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Network Working Group                                     P. Saint-Andre
Internet-Draft                                                 J. Miller
Expires: February 20, March 7, 2004                        Jabber Software Foundation
                                                         August 22,
                                                       September 7, 2003


                         XMPP Instant Messaging
                         draft-ietf-xmpp-im-16
                         draft-ietf-xmpp-im-17

Status of this Memo

   This document is an Internet-Draft and is in full conformance with
   all provisions of Section 10 of RFC2026.

   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF), its areas, and its working groups. Note that other
   groups may also distribute working documents as Internet-Drafts.

   Internet-Drafts are draft documents valid for a maximum of six months
   and may be updated, replaced, or obsoleted by other documents at any
   time. It is inappropriate to use Internet-Drafts as reference
   material or to cite them other than as "work in progress."

   The list of current Internet-Drafts can be accessed at http://
   www.ietf.org/ietf/1id-abstracts.txt.

   The list of Internet-Draft Shadow Directories can be accessed at
   http://www.ietf.org/shadow.html.

   This Internet-Draft will expire on February 20, March 7, 2004.

Copyright Notice

   Copyright (C) The Internet Society (2003). All Rights Reserved.

Abstract

   This document describes specific extensions to and applications of
   the core features of the Extensible Messaging and Presence Protocol (XMPP)
   (XMPP Core [1]) that provide the basic instant messaging and presence
   functionality defined in RFC
   2779. 2779 [2].











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Table of Contents

   1.    Introduction . . . . . . . . . . . . . . . . . . . . . . .    5    6
   1.1   Overview . . . . . . . . . . . . . . . . . . . . . . . . .    5    6
   1.2   Requirements . . . . . . . . . . . . . . . . . . . . . . .    5    6
   1.3   Terminology  . . . . . . . . . . . . . . . . . . . . . . .    5    7
   1.4   Discussion Venue . . . . . . . . . . . . . . . . . . . . .    6    7
   1.5   Intellectual Property Notice . . . . . . . . . . . . . . .    6    7
   2.    Establishing a Session    Syntax of XML Stanzas  . . . . . . . . . . . . . . . . . .    7
   3.    Exchanging Messages    8
   2.1   Message Stanzas  . . . . . . . . . . . . . . . . . . .   10
   3.1   Specifying an Intended Recipient . .    8
   2.1.1 Types of Message . . . . . . . . . . .   10
   3.2   Specifying a Message Type . . . . . . . . . .    8
   2.1.2 Child Elements . . . . . .   10
   3.3   Specifying a Message Body . . . . . . . . . . . . . . . .   11
   3.4   Specifying a Message Subject    9
   2.2   Presence Stanzas . . . . . . . . . . . . . . .   12
   3.5   Specifying a Conversation Thread . . . . . .   10
   2.2.1 Types of Presence  . . . . . . .   12
   4.    Exchanging Presence Information . . . . . . . . . . . . .   14
   4.1   Client and Server Responsibilities   10
   2.2.2 Child Elements . . . . . . . . . . . .   14
   4.2   Specifying Availability Status . . . . . . . . . .   11
   2.3   IQ Stanzas . . . .   17
   4.3   Specifying Detailed Status Information . . . . . . . . . .   17
   4.4   Specifying Presence Priority . . . . . . . . . .   13
   2.4   Extended Namespaces  . . . . .   17
   4.5   Determining When a Contact Went Offline . . . . . . . . .   18
   4.6   Presence Examples . . . . .   13
   3.    Establishing a Session . . . . . . . . . . . . . . . .   19
   5.    Managing Subscriptions . .   15
   4.    Exchanging Messages  . . . . . . . . . . . . . . . .   24
   5.1   Requesting a Subscription . . .   18
   4.1   Specifying an Intended Recipient . . . . . . . . . . . . .   24
   5.2   Handling   18
   4.2   Specifying a Subscription Request Message Type  . . . . . . . . . . . . .   24
   5.3   Cancelling a Subscription from Another Entity . . .   18
   4.3   Specifying a Message Body  . . .   25
   5.4   Unsubscribing from Another Entity's Presence . . . . . . .   25
   6.    Managing One's Roster . . . . . .   18
   4.4   Specifying a Message Subject . . . . . . . . . . . .   26
   6.1   Retrieving One's Roster on Login . . .   19
   4.5   Specifying a Conversation Thread . . . . . . . . . .   26
   6.2   Adding a Roster Item . . .   19
   5.    Exchanging Presence Information  . . . . . . . . . . . . .   21
   5.1   Client and Server Presence Responsibilities  . . .   27
   6.3   Updating a Roster Item . . . .   21
   5.2   Specifying Availability Status . . . . . . . . . . . . . .   28
   6.4   Deleting a Roster Item   24
   5.3   Specifying Detailed Status Information . . . . . . . . . .   24
   5.4   Specifying Presence Priority . . . . . . . .   29
   7.    Integration of Roster Items and Presence Subscriptions . .   30
   7.1   Overview . . . . .   24
   5.5   Presence Examples  . . . . . . . . . . . . . . . . . . . .   30
   7.2   User Subscribes to Contact   25
   6.    Managing Subscriptions . . . . . . . . . . . . . . . .   30
   7.2.1 Alternate Flow: Contact Declines Subscription Request . .   35
   7.3   Creating   29
   6.1   Requesting a Mutual Subscription  . . . . . . . . . . . . . .   36
   7.3.1 Alternate Flow: User Declines . .   29
   6.2   Handling a Subscription Request  . . . .   39
   7.4   Unsubscribing . . . . . . . . .   29
   6.3   Cancelling a Subscription from Another Entity  . . . . . .   30
   6.4   Unsubscribing from Another Entity's Presence . . . . . . .   40
   7.4.1 Case #1: Unsubscribing When Subscription is Not Mutual   30
   7.    Roster Management  . .   40
   7.4.2 Case #2: Unsubscribing When Subscription is Mutual . . . .   43
   7.5   Cancelling a Subscription . . . . . . . . . . . . . .   31
   7.1   Syntax and Semantics . .   45
   7.5.1 Case #1: Cancelling When Subscription is Not Mutual . . .   45
   7.5.2 Case #2: Cancelling When Subscription is Mutual . . . . .   47
   7.6   Removing a Roster Item and Cancelling All Subscriptions .   49
   8.    Subscription States . . . . . . . .   31
   7.2   Business Rules . . . . . . . . . . .   52
   8.1   Defined States . . . . . . . . . . .   31
   7.3   Retrieving One's Roster on Login . . . . . . . . . . .   52
   8.2   Server Handling of Outbound Presence, Categorized by



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         Subscription State . .   32
   7.4   Adding a Roster Item . . . . . . . . . . . . . . . . . .   52
   8.2.1 Subscription State = None .   32
   7.5   Updating a Roster Item . . . . . . . . . . . . . . .   53
   8.2.2 Subscription State = None + Pending Out . . .   34
   7.6   Deleting a Roster Item . . . . . .   53
   8.2.3 Subscription State = None + Pending In . . . . . . . . . .   53
   8.2.4 Subscription State = None + Pending Out/In . .   34
   8.    Integration of Roster Items and Presence Subscriptions . .   36
   8.1   Overview . . . .   53
   8.2.5 Subscription State = To . . . . . . . . . . . . . . . . .   54
   8.2.6 Subscription State = To + Pending In . . . .   36
   8.2   User Subscribes to Contact . . . . . . .   54
   8.2.7 Subscription State = From . . . . . . . . .   36
   8.2.1 Alternate Flow: Contact Declines Subscription Request  . .   41
   8.3   Creating a Mutual Subscription . . . . .   54
   8.2.8 Subscription State = From + Pending Out . . . . . . . . .   54
   8.2.9   42
   8.3.1 Alternate Flow: User Declines Subscription State = Both Request . . . .   45



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   8.4   Unsubscribing  . . . . . . . . . . . .   55
   8.3   Server Handling of Outbound Presence, Categorized by
         Presence Type  . . . . . . . . . . . . . . . . . . . . . .   55
   8.3.1 Subscribe  . . . . . . . . . . . . . . . . .   46
   8.4.1 Case #1: Unsubscribing When Subscription is Not Mutual . .   46
   8.4.2 Case #2: Unsubscribing When Subscription is Mutual . . . .   49
   8.5   Cancelling a Subscription  .   55
   8.3.2 Subscribed . . . . . . . . . . . . . . .   51
   8.5.1 Case #1: Cancelling When Subscription is Not Mutual  . . .   51
   8.5.2 Case #2: Cancelling When Subscription is Mutual  . . . . .   53
   8.6   Removing a Roster Item and Cancelling All Subscriptions  .   55
   8.3.3 Unsubscribe  . . . . .
   9.    Subscription States  . . . . . . . . . . . . . . . . . .   56
   8.3.4 Unsubscribed .   59
   9.1   Defined States . . . . . . . . . . . . . . . . . . . . . .   56
   8.4   59
   9.2   Server Handling of Inbound Outbound Presence, Categorized by
         Subscription State . . . . . . . . . . . . . . . . . . . .   57
   8.4.1   59
   9.2.1 Subscription State = None  . . . . . . . . . . . . . . . .   57
   8.4.2   60
   9.2.2 Subscription State = None + Pending Out  . . . . . . . . .   57
   8.4.3   60
   9.2.3 Subscription State = None + Pending In . . . . . . . . . .   57
   8.4.4   60
   9.2.4 Subscription State = None + Pending Out/In . . . . . . . .   58
   8.4.5   60
   9.2.5 Subscription State = To  . . . . . . . . . . . . . . . . .   58
   8.4.6   61
   9.2.6 Subscription State = To + Pending In . . . . . . . . . . .   58
   8.4.7   61
   9.2.7 Subscription State = From  . . . . . . . . . . . . . . . .   58
   8.4.8   61
   9.2.8 Subscription State = From + Pending Out  . . . . . . . . .   59
   8.4.9   61
   9.2.9 Subscription State = Both  . . . . . . . . . . . . . . . .   59
   8.5   62
   9.3   Server Handling of Inbound Outbound Presence, Categorized by
         Presence Type  . . . . . . . . . . . . . . . . . . . . . .   59
   8.5.1   62
   9.3.1 Subscribe  . . . . . . . . . . . . . . . . . . . . . . . .   59
   8.5.2   62
   9.3.2 Subscribed . . . . . . . . . . . . . . . . . . . . . . . .   60
   8.5.3   62
   9.3.3 Unsubscribe  . . . . . . . . . . . . . . . . . . . . . . .   60
   8.5.4   63
   9.3.4 Unsubscribed . . . . . . . . . . . . . . . . . . . . . . .   60
   8.6   63
   9.4   Server Delivery and Client Acknowledgement Handling of Inbound Presence, Categorized by
         Subscription State Change Notifications . . . . . . . . .   61
   9.    Blocking Communication . . . . . . . . . . .   64
   9.4.1 Subscription State = None  . . . . . . .   62
   9.1   Syntax . . . . . . . . .   64
   9.4.2 Subscription State = None + Pending Out  . . . . . . . . .   64
   9.4.3 Subscription State = None + Pending In . . . . . . . .   62
   9.2   Business Rules . .   64
   9.4.4 Subscription State = None + Pending Out/In . . . . . . . .   65
   9.4.5 Subscription State = To  . . . . . . . . . . . .   64
   9.3   Retrieving One's Privacy Lists . . . . .   65
   9.4.6 Subscription State = To + Pending In . . . . . . . . .   65
   9.4   Managing Active Lists . .   65
   9.4.7 Subscription State = From  . . . . . . . . . . . . . . . .   68
   9.5   Managing the Default List   65
   9.4.8 Subscription State = From + Pending Out  . . . . . . . . .   66
   9.4.9 Subscription State = Both  . . . . . . .   69
   9.6   Editing a Privacy List . . . . . . . . .   66
   9.5   Server Handling of Inbound Presence, Categorized by
         Presence Type  . . . . . . . . .   70
   9.7   Adding a New Privacy List . . . . . . . . . . . . .   66
   9.5.1 Subscribe  . . .   70
   9.8   Removing a Privacy List . . . . . . . . . . . . . . . . .   71
   9.9   Blocking Messages . . . .   66
   9.5.2 Subscribed . . . . . . . . . . . . . . . .   71
   9.10  Blocking Inbound Presence Notifications . . . . . . . .   67
   9.5.3 Unsubscribe  .   73
   9.11  Blocking Outbound Presence Notifications . . . . . . . . .   75
   9.12  Blocking IQs . . . . . . . . . . . . .   67
   9.5.4 Unsubscribed . . . . . . . . . .   76



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   9.13  Blocking All Communication . . . . . . . . . . . . .   67
   9.6   Server Delivery and Client Acknowledgement of
         Subscription State Change Notifications  . . .   78
   9.14  Blocked Entity Attempts to Communicate with User . . . . .   80
   9.15  Higher-Level Heuristics .   68
   10.   Blocking Communication . . . . . . . . . . . . . . . .   80
   10.   Server Rules for Handling XML Stanzas . .   69
   10.1  Syntax and Semantics . . . . . . . .   82
   10.1  No 'to' Address . . . . . . . . . . .   69
   10.2  Business Rules . . . . . . . . . .   82
   10.2  Foreign Domain . . . . . . . . . . . .   71



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   10.3  Retrieving One's Privacy Lists . . . . . . . . . .   82
   10.3  Subdomain . . . .   72
   10.4  Managing Active Lists  . . . . . . . . . . . . . . . . . .   75
   10.5  Managing the Default List  . .   82
   10.4  Bare Domain or Specific Resource . . . . . . . . . . . . .   82
   10.5  User in Same Domain .   76
   10.6  Editing a Privacy List . . . . . . . . . . . . . . . . . .   83
   11.   IANA Considerations   77
   10.7  Adding a New Privacy List  . . . . . . . . . . . . . . . .   78
   10.8  Removing a Privacy List  . . .   85
   11.1  XML Namespace Name for Session Data . . . . . . . . . . .   85
   12.   Security Considerations . . .   78
   10.9  Blocking Messages  . . . . . . . . . . . . . .   86
   13.   Compliance Requirements . . . . . .   78
   10.10 Blocking Inbound Presence Notifications  . . . . . . . . .   80
   10.11 Blocking Outbound Presence Notifications . . .   87
   13.1  Servers . . . . . .   82
   10.12 Blocking IQs . . . . . . . . . . . . . . . . . . .   87
   13.2  Clients . . . .   83
   10.13 Blocking All Communication . . . . . . . . . . . . . . . .   85
   10.14 Blocked Entity Attempts to Communicate with User . . . . .   87
   14.   Differences Between Jabber and XMPP  .
   10.15 Higher-Level Heuristics  . . . . . . . . . .   88
   14.1  Session Creation . . . . . . .   87
   11.   IANA Considerations  . . . . . . . . . . . . . .   88
   14.2  Privacy Rules . . . . .   89
   11.1  XML Namespace Name for Session Data  . . . . . . . . . . .   89
   12.   Internationalization Considerations  . . . . . .   88
         Normative References . . . . .   90
   13.   Security Considerations  . . . . . . . . . . . . . .   89
         Informative References . . .   91
   14.   Server Rules for Handling XML Stanzas  . . . . . . . . . .   92
   15.   Compliance Requirements  . . . . .   90
         Authors' Addresses . . . . . . . . . . . .   94
   15.1  Servers  . . . . . . . .   90
   A.    vCards . . . . . . . . . . . . . . . . .   94
   15.2  Clients  . . . . . . . . .   91
   B.    XML Schemas . . . . . . . . . . . . . . . .   94
         Normative References . . . . . . . . . .   92
   B.1   session . . . . . . . . .   95
         Informative References . . . . . . . . . . . . . . . .   92
   B.2   jabber:iq:last . .   96
         Authors' Addresses . . . . . . . . . . . . . . . . . . . .   92   96
   A.    vCards . . . . . . . . . . . . . . . . . . . . . . . . . .   97
   B.    XML Schemas  . . . . . . . . . . . . . . . . . . . . . . .   98
   B.1   jabber:client namespace  . . . . . . . . . . . . . . . . .   98
   B.2   jabber:server namespace  . . . . . . . . . . . . . . . . .  102
   B.3   jabber:iq:privacy   session  . . . . . . . . . . . . . . . . . . . .   92 . . . . .  106
   B.4   jabber:iq:privacy  . . . . . . . . . . . . . . . . . . . .  106
   B.5   jabber:iq:roster . . . . . . . . . . . . . . . . . . . . .   95  109
   C.    Differences Between Jabber and XMPP  . . . . . . . . . . .  111
   C.1   Session Creation . . . . . . . . . . . . . . . . . . . . .  111
   C.2   Privacy Rules  . . . . . . . . . . . . . . . . . . . . . .  111
   D.    Revision History . . . . . . . . . . . . . . . . . . . . .   97
   C.1  112
   D.1   Changes from draft-ietf-xmpp-im-16 . . . . . . . . . . . .  112
   D.2   Changes from draft-ietf-xmpp-im-15 . . . . . . . . . . . .   97
   C.2  112
   D.3   Changes from draft-ietf-xmpp-im-14 . . . . . . . . . . . .   97
   C.3  113
   D.4   Changes from draft-ietf-xmpp-im-13 . . . . . . . . . . . .   97
   C.4  113
   D.5   Changes from draft-ietf-xmpp-im-12 . . . . . . . . . . . .   97
   C.5  113
   D.6   Changes from draft-ietf-xmpp-im-11 . . . . . . . . . . . .   98
   C.6  113
   D.7   Changes from draft-ietf-xmpp-im-10 . . . . . . . . . . . .   98
   C.7  114
   D.8   Changes from draft-ietf-xmpp-im-09 . . . . . . . . . . . .   98
   C.8  114
   D.9   Changes from draft-ietf-xmpp-im-08 . . . . . . . . . . . .   99
   C.9  114
   D.10  Changes from draft-ietf-xmpp-im-07 . . . . . . . . . . . .   99
   C.10  114
   D.11  Changes from draft-ietf-xmpp-im-06 . . . . . . . . . . . .   99
   C.11  114
   D.12  Changes from draft-ietf-xmpp-im-05 . . . . . . . . . . . .   99
   C.12  115
   D.13  Changes from draft-ietf-xmpp-im-04 . . . . . . . . . . . .   99
   C.13  115



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   D.14  Changes from draft-ietf-xmpp-im-03 . . . . . . . . . . . .  100
   C.14  115
   D.15  Changes from draft-ietf-xmpp-im-02 . . . . . . . . . . . .  100
   C.15  115
   D.16  Changes from draft-ietf-xmpp-im-01 . . . . . . . . . . . .  100
   C.16  116
   D.17  Changes from draft-ietf-xmpp-im-00 . . . . . . . . . . . .  100
   C.17  116
   D.18  Changes from draft-miller-xmpp-im-02 . . . . . . . . . . .  101  116
         Intellectual Property and Copyright Statements . . . . . .  102  117













































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1. Introduction

1.1 Overview

   The core features of the Extensible Messaging and Presence Protocol (XMPP) is a protocol
   for streaming XML [3] elements in order to exchange messages and
   presence information in close to real time. The core features of XMPP
   are defined in XMPP Core [1]. These features -- specifically XML
   streams, stream authentication and encryption, and the <message/>,
   <presence/>, and <iq/> children of the stream root -- provide the
   building blocks for many types of near-real-time applications, which
   may be layered on top of the core by sending application-specific
   data qualified by particular XML namespaces. namespaces [4]. This document
   describes extensions to and applications of XMPP Core that provide
   the basic functionality expected of an instant messaging (IM) and
   presence application as defined in RFC 2779 [2].

1.2 Requirements

   For the purposes of this document, the requirements of a basic
   instant messaging and presence application are defined by RFC 2779
   [2]. At a high level, RFC 2779 stipulates that a user must be able to
   complete the following use cases:

   o  Exchange messages with other users

   o  Exchange presence information with other users

   o  Manage subscriptions to and from other users

   o  Manage items in a contact list (in XMPP this is called a "roster")

   o  Block communications to or from specific other users

   Detailed definitions of these functionality areas are contained in
   RFC 2779, and the interested reader is directed to that document
   regarding the requirements addressed herein.

   Note: while XMPP-based instant messaging and presence meets the
   requirements of RFC 2779, it was not designed explicitly with RFC
   2779 in mind, since the base protocol evolved through an open
   development process within the Jabber open-source community before
   RFC 2779 was written. Note also that although protocols addressing
   many other functionality areas have been defined in the Jabber
   community, such protocols are not included in this document because
   they are not required by RFC 2779 [2].





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1.3 Terminology

   This document inherits the terminology defined in XMPP Core [1].



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   The capitalized key words "MUST", "MUST NOT", "REQUIRED", "SHALL",
   "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED",  "MAY", and
   "OPTIONAL" in this document are to be interpreted as described in RFC
   2119 [3]. [5].

1.4 Discussion Venue

   The authors welcome discussion and comments related to the topics
   presented in this document. The preferred forum is the
   <xmppwg@jabber.org> mailing list, for which archives and subscription
   information are available at <http://www.jabber.org/cgi-bin/mailman/
   listinfo/xmppwg/>.

1.5 Intellectual Property Notice

   This document is in full compliance with all provisions of Section 10
   of RFC 2026. Parts of this specification use the term "jabber" for
   identifying namespaces and other protocol syntax. Jabber[tm] is a
   registered trademark of Jabber, Inc.  Jabber, Inc. grants permission
   to the IETF for use of the Jabber trademark in association with this
   specification and its successors, if any.


























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2. Establishing a Session

   Most Syntax of XML Stanzas

   The basic semantics and common attributes of XML stanzas qualified by
   the 'jabber:client' and 'jabber:server' namespaces are defined in
   XMPP Core [1]. However, these namespaces also define various child
   elements, as well as values for the common 'type' attribute, that are
   specific to instant messaging and presence applications based on applications. Thus, before
   addressing particular "use cases" for such applications, we here
   further describe the syntax of XML stanzas, thereby supplementing the
   discussion in XMPP Core [1].

2.1 Message Stanzas

   Message stanzas in the 'jabber:client' or 'jabber:server' namespace
   are
   implemented via a client-server architecture that requires a user used to
   establish a session on a server in order "push" information to engage another entity. Common uses in the expected
   context of instant messaging and presence activities. However, there are several
   pre-conditions that must be met before a user may establish such a
   session. These include:

   1.  Account Provisioning -- methods for account provisioning include
       account creation by a server administrator as well as in-band
       account registration using single messages, messages sent
   in the 'jabber:iq:register' namespace; context of a chat conversation, messages sent in the latter method context
   of a multi-user chat room, headlines, and errors.

2.1.1 Types of Message

   The 'type' attribute of a message stanza is documented by RECOMMENDED; if included,
   it specifies the Jabber Software Foundation
       [5] at <http://www.jabber.org/protocol/> but is out conversational context of scope for
       this document.

   2.  Authentication and Resource Authorization -- methods for
       completing these pre-conditions are documented the message thus providing
   a hint regarding presentation (e.g., in XMPP Core [1];
       note that client authentication with a server MUST include an
       authorization identity that specifies GUI). If the full JID
       (<user@somedomain/resource>) associated with 'type'
   attribute is included, it SHOULD have one of the connection for
       addressing purposes.

   Once following values
   (any other value MAY be ignored):

   o  chat -- The message is sent in the context of a one-to-one chat
      conversation. A compliant client has authenticated with a server and has authorized a
   full JID, it SHOULD request that the server activate present an instant
   messaging session for interface
      enabling one-to-one chat between the client. This is accomplished two parties, including an
      appropriate conversation history.

   o  error -- An error has occurred related to a previous message sent
      by means of the 'urn:ietf:params:xml:ns:xmpp-session' namespace:

   Step 1: Client requests session with server:

   <iq type='set' id='sess_1'>
     <session xmlns='urn:ietf:params:xml:ns:xmpp-session'/>
   </iq>

   Step 2: Server informs client that session has been created:

   <iq type='result' id='sess_1'/>

   Several sender (for details regarding stanza error conditions are possible. For example, the server may
   encounter syntax, refer to
      XMPP Core [1]). A compliant client SHOULD present an internal condition that prevents it from creating appropriate
      interface informing the
   session, sender of the username or authorization identity may lack permissions
   to create a session, or there may already be an active session
   associated with an authzid nature of the same name.

   If error.

   o  groupchat -- The message is sent in the server encounters context of a multi-user
      chat environment. A compliant client SHOULD present an internal condition that prevents it from
   creating interface
      enabling many-to-many chat between the session, it MUST return parties, including a roster
      of parties in the chatroom and an error.

   Step 2 (alt): Server responds with error (internal server error): appropriate conversation
      history. Full definition of XMPP-based groupchat protocols is out
      of scope for this document.

   o  headline -- The message is probably generated by an automated
      service that delivers or broadcasts content (news, sports, market
      information, RSS feeds, etc.). No reply to the message is
      expected, and a compliant client SHOULD present an interface that



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   <iq type='error' id='sess_1'>
     <session xmlns='urn:ietf:params:xml:ns:xmpp-session'/>
     <error type='wait'>
       <internal-server-error
           xmlns='urn:ietf:params:xml:ns:xmpp-stanzas'/>
     </error>
   </iq>

   If


      appropriately differentiates the username message from standalone messages,
      chat sessions, or authorization identity is groupchat sessions (e.g., by not allowed providing the
      recipient with the ability to create reply).

   o  normal -- The message is a
   session, standalone message to which the server MUST return
      recipient MAY reply if desired.

   An IM application SHOULD support all of the foregoing message types;
   if an error.

   Step 2 (alt): Server responds application receives a message with error (username no 'type' attribute or authzid the
   application does not
   allowed to create session):

   <iq type='error' id='sess_1'>
     <session xmlns='urn:ietf:params:xml:ns:xmpp-session'/>
     <error type='auth'>
       <not-allowed
           xmlns='urn:ietf:params:xml:ns:xmpp-stanzas'/>
     </error>
   </iq>

   If there is already an active session associated with an authzid of understand the same name, value of the server 'type' attribute
   provided, it MUST either (1) terminate the active
   session and allow the newly-requested session, or (2) disallow the
   newly-requested session and maintain consider the existing session. Which message to be of
   these the server does type "normal" (i.e.,
   "normal" is up to the implementation, although it is
   RECOMMENDED to implement (1). In case (1), default).

   Although the server SHOULD send a
   <conflict/> stream error 'type' attribute is NOT REQUIRED, it is considered
   polite to mirror the active session; type in case (2), the
   server SHOULD send a <conflict/> stanza error any replies to the newly-requested
   session.

   Step 2 (alt): Server informs active session of resource conflict
   (case 1):

   <stream:error>
     <conflict xmlns='urn:ietf:params:xml:ns:xmpp-streams'/>
   </stream:error>
   </stream:stream>

   Step 2 (alt): Server informs newly-requested session of resource
   conflict (case 2):

   <iq type='error' id='sess_1'>
     <session xmlns='urn:ietf:params:xml:ns:xmpp-session'/>
     <error type='cancel'>
       <conflict
           xmlns='urn:ietf:params:xml:ns:xmpp-stanzas'/>



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     </error>
   </iq>

   After establishing a session, a client SHOULD send initial presence
   and request its roster as described below, although these actions are
   NOT REQUIRED.













































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3. Exchanging Messages

   Exchanging messages is message; furthermore,
   some specialized applications (e.g., a basic multi-user chat service) MAY
   at their discretion enforce the use of XMPP and is effected when a
   user generates a particular message stanza that is addressed to another user
   (or, more generally, another entity). type
   (e.g., type='groupchat').

2.1.2 Child Elements

   As defined described under Section 10, extended namespaces (Section 2.4), a message
   stanza MAY contain any properly-namespaced child element.

   In accordance with the sender's server default namespace declaration, by default a
   message stanza is responsible for delivering in the 'jabber:client' or 'jabber:server'
   namespace, which defines certain allowable children of message to the
   intended recipient (if
   stanzas. If the recipient message stanza is on the same server) or of type "error", it MUST include an
   <error/> child; for
   routing details, see XMPP Core [1]. Otherwise, the
   message to the recipient's server (if stanza MAY contain any of the recipient is on
   a different server).

   For information regarding the syntax of message stanzas as well as
   their defined attributes and following child elements, refer to XMPP Core [1].

3.1 Specifying an Intended Recipient

   An instant messaging client SHOULD specify elements
   without an intended recipient for
   a message by providing explicit namespace declaration:

   1.  <subject/>

   2.  <body/>

   3.  <thread/>


2.1.2.1 Subject

   The <subject/> element specifies the JID topic of an entity other than the sender in message. The
   <subject/> element SHOULD NOT possess any attributes, with the 'to' attribute
   exception of the <message/> stanza. If the message is being
   sent in reply to a message previously received from an address 'xml:lang' attribute. Multiple instances of the
   form <user@somedomain/resource> (e.g., within
   <subject/> element MAY be included for the context purpose of a chat
   session), the value providing
   alternate versions of the 'to' address SHOULD be the full JID
   (<user@somedomain/resource>) rather than merely <user@somedomain>
   unless same subject, but only if each instance
   possesses an 'xml:lang' attribute with a distinct language value. The
   <subject/> element MUST NOT contain mixed content (as defined in



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   Section 3.2.2 of the sender has knowledge (via presence) that XML specification [3]).

2.1.2.2 Body

   The <body/> element contains the intended
   recipient's resource is no longer available. If textual contents of the message message;
   this child element is being
   sent outside the context of normally included but NOT REQUIRED. The <body/>
   element SHOULD NOT possess any existing chat session or received
   message, attributes, with the value exception of the 'to' address SHOULD be
   'xml:lang' attribute. Multiple instances of the form
   <user@somedomain> rather than <user@somedomain/resource>.

3.2 Specifying <body/> element MAY
   be included but only if each instance possesses an 'xml:lang'
   attribute with a Message Type

   As mentioned in XMPP Core [1], there are several distinct language value. The <body/> element MUST
   NOT contain mixed content (as defined types of
   messages (specified by means of a 'type' attribute within the
   <message/> element). In the context of an instant messaging
   application, a client SHOULD include a message type in order to
   capture the conversational context Section 3.2.2 of the message, thus providing a
   hint regarding presentation (e.g., in XML
   specification [3]).

2.1.2.3 Thread

   The <thread/> element contains a GUI). If the 'type' attribute string that is included, it SHOULD have one of generated by the following values (any other
   value MAY
   sender and that SHOULD be ignored):

   o  chat -- The message is sent copied back in the context of replies; it is used for
   tracking a one-to-one chat
      conversation. A compliant client SHOULD present conversation thread (sometimes referred to as an interface
      enabling one-to-one chat "instant
   messaging session") between the two parties, including an
      appropriate conversation history.

   o  error -- An error has occurred related entities. If used, it MUST be unique
   to a previous message sent
      by that conversation thread within the sender (for details regarding stanza error syntax, refer to
      XMPP Core [1]). A compliant stream and MUST be consistent
   throughout that conversation (a client SHOULD present an appropriate
      interface informing the sender of that receives a message from
   the nature of same full JID but with a different thread ID MUST assume that the error.



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   o  groupchat -- The
   message is sent in question exists outside the context of a multi-user
      chat environment. A compliant client SHOULD present an interface
      enabling many-to-many chat between the parties, including a roster existing
   conversation thread). The use of parties in the chatroom <thread/> element is OPTIONAL
   and an appropriate conversation
      history.

   o  headline -- The message is probably generated by an automated
      service that delivers or broadcasts content (news, sports, market
      information, RSS feeds, etc.). No reply not used to the identify individual messages, only conversations.
   Only one <thread/> element MAY be included in a message is
      expected, stanza, and a compliant client SHOULD present
   it MUST NOT possess any attributes. The <thread/> element MUST be
   treated as an interface that
      appropriately differentiates the message from standalone messages,
      chat sessions, or groupchat sessions (e.g., opaque string by not providing entities; no semantic meaning may be
   derived from it, and only exact comparisons may be made against it.
   The <thread/> element MUST NOT contain mixed content (as defined in
   Section 3.2.2 of the
      recipient XML specification [3]).

2.2 Presence Stanzas

   Presence stanzas are used in the 'jabber:client' or 'jabber:server'
   namespace to express an entity's current availability status (offline
   or online, along with various sub-states of the ability latter and optional
   user-defined descriptive text) and to reply).

   o  normal -- The message is a standalone message communicate that status to
   other entities. Presence stanzas are also used to negotiate and
   manage subscriptions to which the
      recipient MAY reply if desired. This is the default type.

   An IM application SHOULD support all presence of the foregoing message types;
   if an application receives a message with no other entities.

2.2.1 Types of Presence

   The 'type' attribute or the
   application of a presence stanza is OPTIONAL. A presence
   stanza that does not understand the value of the possess a 'type' attribute
   provided, it MUST consider the message is used to signal to be of type "normal".

   Although
   the 'type' attribute is NOT REQUIRED, it server that the sender is considered
   polite to mirror online and available for communication.
   If included, the type in any replies 'type' attribute specifies a lack of availability, a
   request to manage a message; furthermore,
   some specialized applications (e.g., a multi-user chat service) MAY
   at their discretion enforce the use of a particular message type
   (e.g., type='groupchat').

3.3 Specifying a Message Body

   A message stanza MAY (and often will) contain a child <body/> element
   specifying the primary meaning of the message. The content of the
   body element MUST be XML character data and the element MUST NOT
   contain mixed content. If it is necessary to provide the primary
   meaning in an alternate form (e.g., formatted using XHTML), the
   alternate form MUST be contained in some other child of the message
   stanza. However, multiple <body/> elements MAY be included subscription to provide
   the primary meaning in different languages, as long as each such
   element possesses an 'xml:lang' attribute with a distinct value.

   Example: A message with another entity's presence, a body:

   <message
       to='romeo@example.net'
       from='juliet@example.com/balcony'
       xml:lang='en'>
     <body>Wherefore art thou, Romeo?</body>
     <body xml:lang='cz'>Pro&#x010D;e&#x017D; jsi ty, Romeo?</body>



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   </message>


3.4 Specifying


   request for another entity's current presence, or an error related to
   a Message Subject

   A message stanza previously-sent presence stanza. The 'type' attribute MAY contain have one or more child <subject/> elements
   specifying the topic
   of the message. following values:

   o  unavailable -- Signals that the entity is no longer available for
      communication.

   o  subscribe -- The content of sender wishes to subscribe to the subject
   element MUST be XML character data and recipient's
      presence.

   o  subscribed -- The sender has allowed the element MUST NOT contain
   mixed content. Multiple <subject/> elements MAY be included, as long
   as each such element possesses an 'xml:lang' attribute with a
   distinct value.

   Example: recipient to receive
      their presence.

   o  unsubscribe -- A message with a subject:

   <message
       to='romeo@example.net'
       from='juliet@example.com/balcony'
       xml:lang='en'>
     <subject>I implore you!</subject>
     <subject xml:lang='cz'>
       &#x00DA;p&#x011B;nliv&#x011B; prosim!
     </subject>
     <body>Wherefore art thou, Romeo?</body>
     <body xml:lang='cz'>
       Pro&#x010D;e&#x017D; jsi ty, Romeo?
     </body>
   </message>


3.5 Specifying notification that an entity is unsubscribing from
      another entity's presence.

   o  unsubscribed -- The subscription request has been denied or a Conversation Thread
      previously-granted subscription has been cancelled.

   o  probe -- A message request for an entity's current presence; in general,
      SHOULD NOT be sent by a client.

   o  error -- An error has occurred regarding processing or delivery of
      a previously-sent presence stanza.

   For detailed information regarding presence semantics and the
   subscription model used in the context of XMPP-based instant
   messaging and presence applications, refer to the Exchanging Presence
   Information (Section 5) and Managing Subscriptions (Section 6)
   sections of this document.

2.2.2 Child Elements

   As described under extended namespaces (Section 2.4), a presence
   stanza MAY contain a any properly-namespaced child <thread/> element specifying element.

   In accordance with the
   conversation thread default namespace declaration, by default a
   presence stanza is in the 'jabber:client' or 'jabber:server'
   namespace, which defines certain allowable children of presence
   stanzas. If the message presence stanza is situated, for the purpose of tracking type "error", it MUST include
   an <error/> child; for details, see XMPP Core [1]. If the conversation. The content presence
   stanza possesses no 'type' attribute, it MAY contain any of the <thread/> element is
   a random string
   following child elements (note that is generated by the sender in accordance with the algorithm specified in XMPP Core [1]; this string SHOULD <status/> child MAY be
   copied back to the sender sent
   in subsequent replies.

   Example: A threaded conversation:

   <message
       to='romeo@example.net/orchard'
       from='juliet@example.com/balcony'
       type='chat'>
     <body>Art thou not Romeo, and a Montague?</body>
     <thread>e0ffe42b28561960c6b12b944a092794b9683a38</thread>
   </message> presence stanza of type "unavailable" or, for historical
   reasons, "subscribe"):

   1.  <show/>




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   <message
       to='juliet@example.com/balcony'
       from='romeo@example.net/orchard'
       type='chat'>
     <body>Neither, fair saint, if either thee dislike.</body>
     <thread>e0ffe42b28561960c6b12b944a092794b9683a38</thread>
   </message>

   <message
       to='romeo@example.net/orchard'
       from='juliet@example.com/balcony'
       type='chat'>
     <body>How cam'st thou hither, tell me, and wherefore?</body>
     <thread>e0ffe42b28561960c6b12b944a092794b9683a38</thread>
   </message>




































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4. Exchanging Presence Information

   Exchanging presence information is made relatively straightforward
   within XMPP by using presence stanzas. However, we see here a
   contrast to


   2.  <status/>

   3.  <priority/>


2.2.2.1 Show

   The OPTIONAL <show/> element specifies the handling particular availability
   status of messages: although an entity or specific resource (if a client MAY send
   directed presence information to another entity, normally presence
   information <show/> element is sent from a client to its server (with no 'to'
   address) and then broadcasted by the server to any entities that are
   subscribed to the presence of the sending entity. (Note: in the
   terminology of RFC 2778 [6], the only watchers not
   provided, default availability is assumed). Only one <show/> element
   MAY be included in XMPP are
   subscribers.)

   For information regarding the syntax of a presence stanzas as well as
   their defined attributes and child elements, refer to XMPP Core [1].

4.1 Client stanza, and Server Responsibilities

   When a client connects to its server, it SHOULD (but is NOT REQUIRED
   to) send initial presence to possess any
   attributes. The CDATA value SHOULD be one of the server in order to signal its following (values
   other than these four SHOULD be ignored; additional availability for communications. As
   types could be defined herein, through a properly-namespaced child element of
   the initial presence stanza (1) MUST possess no 'to' address (signalling that it stanza):

   o  away -- The entity or resource is meant to be handled by the server on behalf of the user) and (2)
   MUST possess temporarily away.

   o  chat -- The entity or resource is actively interested in chatting.

   o  xa -- The entity or resource is away for an extended period (xa =
      "eXtended Away").

   o  dnd -- The entity or resource is busy (dnd = "Do Not Disturb").

   If no 'type' attribute (signalling the user's
   availability).

   Upon receiving initial presence from a client, the user's server MUST
   do <show/> element is provided, the following:

   1.  Send presence probes (i.e., presence stanzas whose 'type'
       attribute entity is set assumed to be online
   and available.

2.2.2.2 Status

   The OPTIONAL <status/> element contains a value of "probe") from the full JID
       (<user@somedomain/resource>) of the user to the bare JID
       (<contact@otherdomain>) natural-language
   description of any contacts to which the user availability status. It is
       subscribed in order to determine if they are available; such
       contacts are those which are present normally used in the user's roster
   conjunction with the 'subscription' attribute set show element to provide a value detailed description
   of "to" or "both".
       (Note: an availability state (e.g., "In a user or client meeting"). The <status/>
   element SHOULD NOT send presence probes.)

   2.  Broadcast initial presence from possess any attributes, with the full JID (<user@somedomain/
       resource>) exception of the user to the bare JID (<contact@otherdomain>)
   'xml:lang' attribute. Multiple instances of
       any contacts that are subscribed to the user's presence; such
       contacts are those which are present in the user's roster with the 'subscription' <status/> element MAY
   be included but only if each instance possesses an 'xml:lang'
   attribute set to a value of "from" or "both".

   Upon receiving with a presence probe from distinct language value.

2.2.2.3 Priority

   The OPTIONAL <priority/> element specifies the user, the contact's server
   MUST send to the user the last known availability information (i.e.,
   the full XML priority level of the last
   connected resource. The value may be any integer between -128 and
   +127. Only one <priority/> element MAY be included in a presence stanza) provided by each of the
   contact's active sessions (if there exist
   stanza, and it MUST NOT possess any attributes. If no active sessions, the priority is
   provided, a server SHOULD NOT reply consider the priority to be zero. For
   information regarding the semantics of priority values in stanza
   routing within instant messaging and presence probe). The server MUST send applications, refer to



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   this information subject to domain-specific access rules, and only if
   the user is in


   the contact's roster with Server Rules for Handling XML Stanzas (Section 14) section of
   this document.

2.3 IQ Stanzas

   IQ stanzas provide a subscription state structured request-response mechanism. The basic
   semantics of
   "from" or "both" and that mechanism are defined in XMPP Core [1], whereas the contact has not blocked outbound presence
   notifications
   specific semantics required to the user's bare or full JID (as complete particular use cases are
   defined in Section
   9.11). (Note: if all cases by an extended namespace (Section 2.4) (note
   that the server receives a presence probe from a
   subdomain 'jabber:client' and 'jabber:server' namespaces do not define
   any children of the server's hostname or another IQ stanzas). This document defines two such trusted service,
   it extended
   namespaces, one for Roster Management (Section 7) and the other for
   Blocking Communication (Section 10); however, an IQ stanza MAY provide presence
   contain structured information about qualified by any extended namespace.

2.4 Extended Namespaces

   While the user to that entity.)

   Upon receiving initial presence from three XML stanza kinds defined in the user, "jabber:client" or
   "jabber:server" namespace (along with their attributes and child
   elements) provide a basic level of functionality for messaging and
   presence, XMPP uses XML namespaces to extend the contact's server
   MUST deliver stanzas for the user's presence
   purpose of providing additional functionality. Thus a message,
   presence, or IQ stanza to MAY house one or more optional child elements
   containing content that extends the full JIDs
   (<contact@otherdomain/resource>) associated with all meaning of the contact's
   active sessions, but only if message (e.g., an
   XHTML-formatted version of the user message body). This child element MAY
   have any name and MUST possess an 'xmlns' namespace declaration
   (other than "jabber:client", "jabber:server", or "http://
   etherx.jabber.org/streams") that defines all data contained within
   the child element.

   Support for any given extended namespace is in OPTIONAL on the contact's roster with
   a subscription state part of "to" or "both" and the contact has
   any implementation. If an entity does not
   blocked inbound presence notifications from understand such a
   namespace, the user's bare entity's expected behavior depends on whether the
   entity is (1) the recipient or full
   JID (as defined in Section 9.10).

   If (2) an entity that is routing the user's server receives a presence
   stanza of type "error" in
   response to the initial presence recipient:

   Recipient: If a recipient receives a stanza that it forwarded to contains a contact on
   behalf of the user, child
      element it does not understand, it SHOULD NOT send further presence updates to ignore that contact (until and unless specific XML
      data, i.e., it receives SHOULD not process it or present it to a presence probe from the
   contact).

   After sending initial presence, the user MAY update and broadcast its
   presence information at any time during its active session by sending or
      associated application (if any). In particular:

      *  If an entity receives a message or presence stanza with no 'to' address and either no 'type' attribute
   or a 'type' attribute with a value of "unavailable". (Note: a user's
   client SHOULD NOT send a presence update to broadcast information that changes independently of the user's presence and availability.)
   If the presence stanza lacks a 'type' attribute (i.e., expresses
   availability), the user's server MUST broadcast the full
         contains XML of that
   presence stanza to all contacts (1) that are in the user's roster
   with data qualified by a subscription type of "from" or "both", (2) to whom the user
   has not blocked outbound presence, and (3) from whom the server has namespace it does not received a presence error during the user's session. If
         understand, the
   presence stanza has a 'type' attribute set to a value portion of
   "unavailable", the user's server MUST broadcast the full XML of that
   presence stanza to all contacts meeting the three conditions just
   mentioned, as well as to any entities to which the user has sent
   directed available presence during the user's session (if the user
   has not yet sent directed unavailable presence to that entity).

   A user MAY send directed presence to another entity (i.e., a presence
   stanza with a 'to' attribute whose value is in the JID of the other unknown
         namespace SHOULD be ignored.

      *  If an entity and with either no 'type' attribute or receives a 'type' attribute
   whose value is "unavailable"). There are three possible cases:

   1.  If the user sends directed presence to message stanza containing only a contact that is in the
       user's roster with child
         element qualified by a subscription type of "from" or "both" after namespace it does not understand, it



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       having sent initial presence and before sending unavailable
       presence broadcast, the user's server


         MUST route ignore the entire stanza.

      *  If an entity receives an IQ stanza of type "get" or deliver "set"
         containing a child element qualified by a namespace it does not
         understand, the
       full XML entity SHOULD return an IQ stanza of that presence type
         "error" with an error condition of <feature-not-implemented/>.

   Router: If a routing entity (usually a server) handles a stanza (subject to privacy rules) but
       SHOULD NOT otherwise modify the contact's status regarding
       presence broadcast (i.e., that
      contains a child element it does not understand, it SHOULD include ignore
      the contact's JID in
       any subsequent presence broadcasts initiated associated XML data by the user).

   2.  If the user sends directed presence passing it on untouched to an entity that is not in the user's roster with
      recipient.








































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3. Establishing a subscription type of "from" or "both"
       after having sent initial presence Session

   Most instant messaging and before sending unavailable presence broadcast, the user's server MUST route or deliver the
       full XML of applications based on XMPP are
   implemented via a client-server architecture that presence stanza requires a user to the entity but MUST NOT
       modify the contact's status regarding available presence
       broadcast (i.e., it MUST NOT include the entity's JID
   establish a session on a server in order to engage in any
       subsequent broadcasts of available presence initiated by the
       user); however, if the connected resource from which the user
       sent the directed expected
   instant messaging and presence become unavailable, the user's server
       MUST broadcast activities. However, there are several
   pre-conditions that unavailable presence to the entity (if the
       user has not yet sent directed unavailable presence to that
       entity).

   3.  If the user sends directed presence without first sending initial
       presence or after having sent unavailable presence broadcast, the
       user's server MUST treat the entities to which the user sends
       directed presence in the same way that it treats the entities
       listed in Case 2 above.

   Before ending its session with must be met before a server, user may establish such a client SHOULD gracefully
   become unavailable
   session. These include:

   1.  Account Provisioning -- methods for account provisioning include
       account creation by sending a final presence stanza that possesses
   no 'to' attribute and that possesses a 'type' attribute whose value
   is "unavailable" (optionally, the final presence stanza MAY contain
   one or more <status/> elements specifying server administrator as well as in-band
       account registration using the reason why 'jabber:iq:register' namespace;
       the user latter method is
   no longer available). However, documented by the user's Jabber Software Foundation
       [7] at <http://www.jabber.org/protocol/> but is out of scope for
       this document.

   2.  Authentication and Resource Authorization -- methods for
       completing these pre-conditions are documented in XMPP Core [1];
       note that client authentication with a server MUST NOT depend on
   receiving final presence from include an available resource, since the
   resource may become unavailable unexpectedly. If the user's server
   detects
       authorization identity that one of specifies the user's resources has become unavailable full JID
       (<user@somedomain/resource>) associated with the connection for
   any reason (either gracefully or ungracefully), it MUST broadcast
   unavailable presence
       addressing purposes.

   Before attempting to all contacts (1) that are in the user's
   roster establish a session, a client MUST authenticate
   with a subscription type of "from" or "both", (2) to whom the
   user has not blocked outbound presence, and (3) from whom the server
   has not received and authorize a presence error during the user's session; the
   user's server full JID; in order to then establish a
   session, it MUST also send that unavailable presence stanza to any
   entities to which a session activation request (an IQ set
   containing a <session/gt; child element qualified by the user
   'urn:ietf:params:xml:ns:xmpp-session' namespace) as follows:

   Step 1: Client requests session with server:

   <iq type='set' id='sess_1'>
     <session xmlns='urn:ietf:params:xml:ns:xmpp-session'/>
   </iq>

   Step 2: Server informs client that session has sent directed presence during been created:

   <iq type='result' id='sess_1'/>

   Several error conditions are possible. For example, the
   user's session for server may
   encounter an internal condition that resource (if prevents it from creating the user has not yet sent
   directed unavailable presence
   session, the username or authorization identity may lack permissions
   to that entity). Any presence stanza
   with no 'type' attribute and no 'to' attribute that is sent after
   sending directed unavailable presence create a session, or broadcasted unavailable
   presence MUST there may already be broadcasted by an active session
   associated with an authzid of the same name.

   If the server to all subscribers. encounters an internal condition that prevents it from
   creating the session, it MUST return an error.




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4.2 Specifying Availability Status

   A client MAY provide further information about its availability
   status by using the <show/> element. As mentioned in XMPP Core [1],
   the recognized values for


   Step 2 (alt): Server responds with error (internal server error):

   <iq type='error' id='sess_1'>
     <session xmlns='urn:ietf:params:xml:ns:xmpp-session'/>
     <error type='wait'>
       <internal-server-error
           xmlns='urn:ietf:params:xml:ns:xmpp-stanzas'/>
     </error>
   </iq>

   If the show element are:

   o  away -- The entity or resource is temporarily away.

   o  chat -- The entity username or resource authorization identity is actively interested in chatting.

   o  xa -- The entity not allowed to create a
   session, the server MUST return an error.

   Step 2 (alt): Server responds with error (username or resource authzid not
   allowed to create session):

   <iq type='error' id='sess_1'>
     <session xmlns='urn:ietf:params:xml:ns:xmpp-session'/>
     <error type='auth'>
       <not-allowed
           xmlns='urn:ietf:params:xml:ns:xmpp-stanzas'/>
     </error>
   </iq>

   If there is away for already an extended period (xa =
      "eXtended Away").

   o  dnd -- The entity active session associated with an authzid of
   the same name, the server MUST either (1) terminate the active
   session and allow the newly-requested session, or resource is busy (dnd = "Do Not Disturb").

   Example: Availability status:

   <presence>
     <show>dnd</show>
   </presence>

   If no <show/> element (2) disallow the
   newly-requested session and maintain the existing session. Which of
   these the server does is provided, up to the entity implementation, although it is assumed
   RECOMMENDED to be online
   and available.

4.3 Specifying Detailed Status Information implement (1). In conjunction with case (1), the  <show/> element, server SHOULD send a client MAY provide
   detailed status information by using
   <conflict/> stream error to the <status/> element. The
   content of this element is active session; in case (2), the
   server SHOULD send a natural-language description of <conflict/> stanza error to the
   user's current availability status. The content newly-requested
   session.

   Step 2 (alt): Server informs active session of the status element
   MUST be XML character data and the element MUST NOT contain mixed
   content. Multiple <status/> elements MAY be included, as long as each
   such element possesses an 'xml:lang' attribute with a distinct value.

   Example: Detailed status information:

   <presence xml:lang='en'>
     <show>dnd</show>
     <status>Wooing Juliet</status>
     <status xml:lang='cz'>Ja dvo&#x0159;&#x00ED;m Juliet</status>
   </presence>


4.4 Specifying Presence Priority

   A client MAY provide a priority for its resource by using the
   <priority/> element. The content conflict
   (case 1):

   <stream:error>
     <conflict xmlns='urn:ietf:params:xml:ns:xmpp-streams'/>
   </stream:error>
   </stream:stream>

   Step 2 (alt): Server informs newly-requested session of this element is an integer whose
   value is between -128 and +127. If a client does not provide the resource
   conflict (case 2):

   <iq type='error' id='sess_1'>
     <session xmlns='urn:ietf:params:xml:ns:xmpp-session'/>
     <error type='cancel'>



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   priority element in


       <conflict
           xmlns='urn:ietf:params:xml:ns:xmpp-stanzas'/>
     </error>
   </iq>

   After establishing a session, a client SHOULD send initial presence stanza,
   and request its server SHOULD assume that
   the priority value roster as described below, although these actions are
   NOT REQUIRED.











































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4. Exchanging Messages

   Exchanging messages is zero.

   Example: Presence priority:

   <presence xml:lang='en'>
     <show>dnd</show>
     <status>Wooing Juliet</status>
     <status xml:lang='cz'>Ja dvo&#x0159;&#x00ED;m Juliet</status>
     <priority>1</priority>
   </presence>


4.5 Determining When a Contact Went Offline

   The server MUST maintain a record basic use of the time at which XMPP and is effected when a
   user became
   unavailable (whether gracefully or ungracefully). An authorized
   subscriber to that user's presence MAY request the time of last
   activity by sending an IQ generates a message stanza that is addressed to another user
   (or, more generally, another entity). As defined under Server Rules
   for Handling XML Stanzas (Section 14), the user's bare JID
   (<user@somedomain>) containing an empty <query/> element qualified by sender's server is
   responsible for delivering the 'jabber:iq:last' namespace:

   Example: Requesting message to the last active time of an offline user:

   <iq type='get' to='user@somedomain'>
     <query xmlns='jabber:iq:last'/>
   </iq>

   If intended recipient (if
   the entity requesting the time of last activity recipient is an authorized
   subscriber on the same server) or for routing the message to
   the user's presence (i.e., exists in recipient's server (if the user's roster
   with recipient is on a different server).

   For information regarding the 'subscription' attribute set syntax of message stanzas as well as
   their defined attributes and child elements, refer to XMPP Core [1].

4.1 Specifying an Intended Recipient

   An instant messaging client SHOULD specify an intended recipient for
   a value message by providing the JID of "from" or "both")
   and an entity other than the user sender in
   the 'to' attribute of the <message/> stanza. If the message is not blocking IQ stanzas being
   sent in reply to and a message previously received from an address of the entity (as
   defined in Section 9.12),
   form <user@somedomain/resource> (e.g., within the server SHOULD return an IQ stanza context of
   type "result" with a chat
   session), the number value of seconds since the user was last
   active:

   Example: Returning 'to' address SHOULD be the last active time of an offline user:

   <iq from='user@somedomain'
       type='result'
       to='contact@otherdomain/resource'>
     <query seconds='76490' xmlns='jabber:iq:last'/>
   </iq>

   If full JID
   (<user@somedomain/resource>) rather than merely <user@somedomain>
   unless the entity requesting sender has knowledge (via presence) that the time of last activity intended
   recipient's resource is not an
   authorized subscriber to the user's presence (i.e., does not exist in no longer available. If the user's roster with message is being
   sent outside the 'subscription' attribute set to a value context of
   "from" any existing chat session or "both"), received
   message, the server MUST return an IQ stanza of type



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   "error" with an error condition value of forbidden:

   Example: Requester is forbidden to view the last active time of an
   offline user:

   <iq from='user@somedomain'
       type='error'
       to='contact@otherdomain/resource'>
     <query xmlns='jabber:iq:last'/>
     <error type='auth'>
       <forbidden
           xmlns='urn:ietf:params:xml:ns:xmpp-stanzas'/>
     </error>
   </iq>

   Note: this document defines responses to requests for last active
   time only with regard to JIDs 'to' address SHOULD be of the form <user@somedomain>, and only
   with regard to JIDs that correspond to an (offline) instant messaging
   user. The behavior of other JID forms (e.g., <user@somedomain/
   resource> or <somedomain>) and entity types (e.g., online user or
   host) is out
   <user@somedomain> rather than <user@somedomain/resource>.

4.2 Specifying a Message Type

   xxx

4.3 Specifying a Message Body

   A message stanza MAY (and often will) contain a child <body/> element
   specifying the primary meaning of scope and undefined.

4.6 Presence Examples

   The examples in this section illustrate the presence-related
   protocols described above. message. The user is romeo@example.net, he has
   authorized a resource "orchard", content of the
   body element MUST be XML character data and he has the following individuals element MUST NOT
   contain mixed content (as defined in his roster:

   o  juliet@example.com (subscription="both" and she has two active
      sessions, one whose resource is "chamber" and another whose
      resource is "balcony")

   o  benvolio@example.org (subscription="to")

   o  mercutio@shakespeare.lit (subscription="from")

   Example 1: User sends initial presence:

   <presence/>

   Example 2: User's server sends presence probe to contacts with
   subscription="to" and subscription="both" on behalf Section 3.2.2 of the user's
   connected resource:

   <presence
       type='probe'
       from='romeo@example.net/orchard'



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       to='juliet@example.com'/>

   <presence
       type='probe'
       from='romeo@example.net/orchard'
       to='benvolio@example.org'/>

   Example 3: User's server sends initial presence XML
   specification [3]). If it is necessary to contacts with
   subscription="from" and subscription="both" on behalf provide the primary meaning
   in an alternate form (e.g., formatted using XHTML), the alternate
   form MUST be contained in some other child of the user's
   connected resource:

   <presence
       from='romeo@example.net/orchard'
       to='juliet@example.com'/>

   <presence
       from='romeo@example.net/orchard'
       to='mercutio@shakespeare.lit'/>

   Example 4: Contacts' server replies to presence probe on behalf of
   all of the contact's available resources:

   <presence
       from='juliet@example.com/balcony'
       to='romeo@example.net/orchard'
       xml:lang='en'>
     <show>away</show>
     <status>be right back</status>
     <priority>0</priority>
   </presence>

   <presence
       from='juliet@example.com/chamber'
       to='romeo@example.net/orchard'>
     <priority>1</priority>
   </presence>

   <presence
       from='benvolio@example.org/pda'
       to='romeo@example.net/orchard'
       xml:lang='en'>
     <show>dnd</show>
     <status>gallivanting</status>
   </presence>

   Example 5: Contact's server delivers user's initial presence message stanza.
   However, multiple <body/> elements MAY be included to all
   of provide the contact's available resources or returns error to user:
   primary meaning in different languages, as long as each such element
   possesses an 'xml:lang' attribute with a distinct value.

   Example: A message with a body:

   <message



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   <presence
       from='romeo@example.net/orchard'
       to='juliet@example.com/chamber'/>

   <presence
       from='romeo@example.net/orchard'
       to='juliet@example.com/balcony'/>

   <presence
       type='error'
       from='mercutio@shakespeare.lit'
       to='romeo@example.net/orchard'>
     <error type='cancel'>
       <remote-server-not-found
           xmlns='urn:ietf:params:xml:ns:xmpp-stanzas'/>
     </error>
   </presence>

   Example 6: User sends directed presence to another user not in his
   roster:

   <presence
       from='romeo@example.net/orchard'
       to='nurse@example.com'
       xml:lang='en'>
     <show>dnd</show>
     <status>courting Juliet</status>
     <priority>0</priority>
   </presence>

   Example 7: User sends updated available presence information for
   broadcasting:

   <presence


       to='romeo@example.net'
       from='juliet@example.com/balcony'
       xml:lang='en'>
     <show>away</show>
     <status>I shall return!</status>
     <priority>1</priority>
   </presence>

   Example 8: Updated presence information is delivered only to
     <body>Wherefore art thou, Romeo?</body>
     <body xml:lang='cz'>Pro&#x010D;e&#x017D; jsi ty, Romeo?</body>
   </message>


4.4 Specifying a Message Subject

   A message stanza MAY contain one
   contact (not those from whom an error was received or to whom more child <subject/> elements
   specifying the
   user sent directed presence):

   <presence
       from='romeo@example.net/orchard'
       to='juliet@example.com/chamber'
       xml:lang='en'>
     <show>away</show>



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     <status>I shall return!</status>
     <priority>1</priority>
   </presence>

   <presence
       from='romeo@example.net/orchard'
       to='juliet@example.com/balcony'
       xml:lang='en'>
     <show>away</show>
     <status>I shall return!</status>
     <priority>1</priority>
   </presence>

   Example 9: One topic of the contact's resources sends final presence:

   <presence type='unavailable'/>

   Example 10: Contact's server sends unavailable presence information
   to user:

   <presence
       type='unavailable' message. The content of the subject
   element MUST be XML character data and the element MUST NOT contain
   mixed content (as defined in Section 3.2.2 of the XML specification
   [3]). Multiple <subject/> elements MAY be included, as long as each
   such element possesses an 'xml:lang' attribute with a distinct value.

   Example: A message with a subject:

   <message
       to='romeo@example.net'
       from='juliet@example.com/balcony'
       to='romeo@example.net/orchard'/>

   Example 11: User sends final presence:

   <presence type='unavailable'
       xml:lang='en'>
     <status>gone home</status>
   </presence>

   Example 12: Unavailable presence information
     <subject>I implore you!</subject>
     <subject xml:lang='cz'>
       &#x00DA;p&#x011B;nliv&#x011B; prosim!
     </subject>
     <body>Wherefore art thou, Romeo?</body>
     <body xml:lang='cz'>
       Pro&#x010D;e&#x017D; jsi ty, Romeo?
     </body>
   </message>


4.5 Specifying a Conversation Thread

   A message stanza MAY contain a child <thread/> element specifying the
   conversation thread in which the message is delivered to
   contact's one remaining resource as well as to situated, for the person purpose
   of tracking the conversation. The content of the <thread/> element is
   a random string that is generated by the sender in accordance with
   the algorithm specified in XMPP Core [1]; this string SHOULD be
   copied back to whom the
   user sent directed presence:

   <presence
       type='unavailable'
       from='romeo@example.net/orchard'
       to='juliet@example.com/chamber'
       xml:lang='en'>
     <status>gone home</status>
   </presence>

   <presence
       from='romeo@example.net/orchard'
       to='nurse@example.com'
       xml:lang='en'>
     <status>gone home</status> sender in subsequent replies.

   Example: A threaded conversation:

   <message
       to='romeo@example.net/orchard'
       from='juliet@example.com/balcony'



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   </presence>


       type='chat'>
     <body>Art thou not Romeo, and a Montague?</body>
     <thread>e0ffe42b28561960c6b12b944a092794b9683a38</thread>
   </message>

   <message
       to='juliet@example.com/balcony'
       from='romeo@example.net/orchard'
       type='chat'>
     <body>Neither, fair saint, if either thee dislike.</body>
     <thread>e0ffe42b28561960c6b12b944a092794b9683a38</thread>
   </message>

   <message
       to='romeo@example.net/orchard'
       from='juliet@example.com/balcony'
       type='chat'>
     <body>How cam'st thou hither, tell me, and wherefore?</body>
     <thread>e0ffe42b28561960c6b12b944a092794b9683a38</thread>
   </message>































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5. Managing Subscriptions

   In order to protect the privacy of instant messaging users and any
   other entities, Exchanging Presence Information

   Exchanging presence and availability information is disclosed
   only made relatively straightforward
   within XMPP by using presence stanzas. However, we see here a
   contrast to other entities that the user has approved. When handling of messages: although a user has
   agreed that client MAY send
   directed presence information to another entity may view entity, normally presence
   information is sent from a client to its presence, server (with no 'to'
   address) and then broadcasted by the entity is said server to have a subscription any entities that are
   subscribed to the user's presence information. A
   subscription lasts across sessions; indeed, it lasts until of the
   subscriber unsubscribes or sending entity. (Note: in the subscribee cancels
   terminology of RFC 2778 [8], we can say that the
   previously-granted subscription. Subscriptions are managed within only watchers in
   XMPP by sending are subscribers.)

   For information regarding the syntax of presence stanzas containing specially-defined
   attributes.

   Note: there are important interactions between subscriptions and
   rosters; these are as well as
   their defined under Integration of Roster Items and
   Presence Subscriptions (Section 7), attributes and the reader must child elements, refer to that
   section for a complete understanding of presence subscriptions. XMPP Core [1].

5.1 Requesting Client and Server Presence Responsibilities

   When a Subscription

   A request to subscribe client connects to another entity's presence its server, it SHOULD (but is made by
   sending a NOT REQUIRED
   to) send initial presence stanza of type "subscribe".

   Example: Sending a subscription request:

   <presence to='juliet@example.com' type='subscribe'/>

   If the subscription request is being sent to another instant
   messaging user, the JID supplied server in the 'to' attribute SHOULD be of
   the form <contact@otherdomain> rather than <contact@otherdomain/
   resource>.

   A user's server order to signal its
   availability for communications. As defined herein, the initial
   presence stanza (1) MUST NOT automatically approve subscription requests possess no 'to' address (signalling that it
   is meant to be handled by the server on behalf of the user's behalf. All subscription requests user) and (2)
   MUST be directed to possess no 'type' attribute (signalling the user's client. If there is no available resource associated with
   availability).

   Upon receiving initial presence from a client, the user when user's server MUST
   do the subscription request following:

   1.  Send presence probes (i.e., presence stanzas whose 'type'
       attribute is received by set to a value of "probe") from the server, full JID
       (<user@somedomain/resource>) of the
   user's server MUST store user to the subscription request offline for
   delivery when bare JID
       (<contact@otherdomain>) of any contacts to which the user next becomes available. (Note: is
       subscribed in order to determine if a resource
   has authorized a session but has not provided initial presence, they are available; such
       contacts are those which are present in the
   server SHOULD NOT consider it to be available and therefore SHOULD
   NOT send subscription requests user's roster with
       the 'subscription' attribute set to it.)

5.2 Handling a Subscription Request

   When value of "to" or "both".
       (Note: a user or client receives a subscription request SHOULD NOT send presence probes.)

   2.  Broadcast initial presence from another entity, it
   MUST either approve the request by sending a presence stanza full JID (<user@somedomain/
       resource>) of type
   "subscribed" or refuse the request by sending a presence stanza user to the bare JID (<contact@otherdomain>) of
   type "unsubscribed".



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   Example: Approving a subscription request:

   <presence to='romeo@example.net' type='subscribed'/>

   Example: Refusing a presence subscription request:

   <presence to='romeo@example.net' type='unsubscribed'/>


5.3 Cancelling a Subscription from Another Entity

   If a user would like
       any contacts that are subscribed to the user's presence; such
       contacts are those which are present in the user's roster with
       the 'subscription' attribute set to cancel a previously-granted subscription
   request, it sends a presence stanza value of type "unsubscribed".

   Example: Cancelling "from" or "both".

   Upon receiving a previously granted subscription request:

   <presence to='romeo@example.net' type='unsubscribed'/>


5.4 Unsubscribing presence probe from Another Entity's Presence

   If a user would like the user, the contact's server
   MUST send to unsubscribe from the presence user the last known availability information (i.e.,
   the full XML of another
   entity, it sends a the last presence stanza stanza) provided by each of type "unsubscribe".

   Example: Unsubscribing from an entity's presence:

   <presence to='juliet@example.com' type='unsubscribe'/> the
   contact's active sessions (if there exist no active sessions, the
   server SHOULD NOT reply to the presence probe). The server MUST send



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6. Managing One's Roster

   In XMPP, one's contact list


   this information subject to domain-specific access rules, and only if
   the user is called a roster, which consists of any
   number of specific roster items, each in the contact's roster item being identified by with a unique JID (usually subscription state of
   "from" or "both" and the form <contact@otherdomain>). A user's
   roster is stored by contact has not blocked outbound presence
   notifications to the user's server on bare or full JID (as defined under
   Blocking Outbound Presence Notifications (Section 10.11)). (Note: if
   the user's behalf so that
   the user may access roster information server receives a presence probe from any available resource.

   Note: there are important interactions between rosters and
   subscriptions; these are defined under Integration of Roster Items
   and Presence Subscriptions (Section 7), and the reader must refer to
   that section for a complete understanding subdomain of roster management.

   Note: a server MUST ignore any 'to' address on a roster "set", and
   MUST treat any roster "set" as applying to the sender. For added
   safety, a client SHOULD check server's
   hostname or another such trusted service, it MAY provide presence
   information about the "from" address of a roster "push" user to ensure that it is entity.)

   Upon receiving initial presence from a trusted source; specifically, the user, the contact's server
   MUST deliver the user's presence stanza
   should have no 'from' attribute (i.e., implicitly from to the server) or full JIDs
   (<contact@otherdomain/resource>) associated with all of the JID contained contact's
   active sessions, but only if the user is in the 'from' attribute should match contact's roster with
   a subscription state of "to" or "both" and the contact has not
   blocked inbound presence notifications from the user's bare JID or full JID; otherwise, the client SHOULD ignore
   JID (as defined under Blocking Inbound Presence Notifications
   (Section 10.10)).

   If the roster
   "push".

6.1 Retrieving One's Roster on Login

   Upon connecting user's server receives a presence stanza of type "error" in
   response to the server, initial presence that it forwarded to a client contact on
   behalf of the user, it SHOULD request NOT send further presence updates to
   that contact (until and unless it receives a presence probe from the roster
   (however, because receiving
   contact).

   After sending initial presence, the roster may not be desirable for all
   resources, e.g., a connection with limited bandwidth, the client's
   request for the roster is NOT REQUIRED). If an available resource
   does not request the roster user MAY update and broadcast its
   presence information at any time during its active session by sending
   a session, the server SHOULD NOT
   send it presence subscriptions stanza with no 'to' address and associated "roster pushes".

   Example: Client requests current roster from server:

   <iq type='get' id='roster_1'>
     <query xmlns='jabber:iq:roster'/>
   </iq>

   Example: Client receives roster from the server:

   <iq id='roster_1' type='result'>
     <query xmlns='jabber:iq:roster'>
       <item jid='romeo@example.net'
             name='Romeo'
             subscription='both'>
         <group>Friends</group>
       </item>
       <item jid='mercutio@shakespeare.lit'
             name='Mercutio'



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             subscription='both'>
         <group>Friends</group>
       </item>
       <item jid='benvolio@example.org'
             name='Benvolio'
             subscription='both'>
         <group>Friends</group>
       </item>
     </query>
   </iq>


6.2 Adding a Roster Item

   At any time, a user MAY add an item to his either no 'type' attribute
   or her roster.

   Example: Client adds a new item:

   <iq type='set' id='roster_2'>
     <query xmlns='jabber:iq:roster'>
       <item jid='nurse@example.com'
             name='Nurse'>
         <group>Servants</group>
       </item>
     </query>
   </iq>

   The 'type' attribute with a value of the 'jid' attribute "unavailable". (Note: a user's
   client SHOULD be NOT send a presence update to broadcast information
   that changes independently of the form
   <user@somedomain>, especially if user's presence and availability.)
   If the item is associated with another
   (human) instant messaging user.

   The presence stanza lacks a 'type' attribute (i.e., expresses
   availability), the user's server MUST update the roster information in persistent storage,
   and also push broadcast the change out full XML of that
   presence stanza to all of the user's available resources contacts (1) that have requested are in the roster. This "roster push" consists user's roster
   with a subscription type of an IQ
   set "from" or "both", (2) to whom the user
   has not blocked outbound presence, and (3) from whom the server has
   not received a presence error during the user's session. If the
   presence stanza has a 'type' attribute set to a value of
   "unavailable", the client and enables user's server MUST broadcast the full XML of that
   presence stanza to all contacts meeting the three conditions just
   mentioned, as well as to any entities to which the user has sent
   directed available resources presence during the user's session (if the user
   has not yet sent directed unavailable presence to remain in sync that entity).

   A user MAY send directed presence to another entity (i.e., a presence
   stanza with a 'to' attribute whose value is the server-based roster information.

   Example: Server (1) pushes JID of the updated roster information to all
   available resources other
   entity and (2) replies with an IQ result to the sending
   resource:

   <iq type='set'>
     <query xmlns='jabber:iq:roster'>
       <item jid='nurse@example.com'
             name='Nurse'
             subscription='none'>
         <group>Servants</group>
       </item> either no 'type' attribute or a 'type' attribute
   whose value is "unavailable"). There are three possible cases:




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     </query>
   </iq>

   <iq type='set'>
     <query xmlns='jabber:iq:roster'>
       <item jid='nurse@example.com'
             name='Nurse'
             subscription='none'>
         <group>Servants</group>
       </item>
     </query>
   </iq>

   <iq type='result' id='roster_2'/>

   Example: Connected resources reply with an IQ result to


   1.  If the server:

   <iq from='juliet@example.com/balcony'
       to='example.com'
       type='result'/>
   <iq from='juliet@example.com/chamber'
       to='example.com'
       type='result'/>


6.3 Updating user sends directed presence to a Roster Item

   Updating an existing roster item (e.g., changing the group) contact that is done in the same way as adding a new roster item, i.e., by sending the
       user's roster item in an IQ set to the server.

   Example: User updates roster item (added group):

   <iq type='set' id='roster_3'>
     <query xmlns='jabber:iq:roster'>
       <item jid='romeo@example.net'
             name='Romeo'
             subscription='both'>
         <group>Friends</group>
         <group>Lovers</group>
       </item>
     </query>
   </iq>

   As with adding a roster item, when updating a roster item subscription type of "from" or "both" after
       having sent initial presence and before sending unavailable
       presence broadcast, the user's server MUST update route or deliver the roster information in persistent storage, and also
   initiate a "roster push" to all
       full XML of the user's available resources that have requested presence stanza (subject to privacy rules) but
       SHOULD NOT otherwise modify the roster.



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6.4 Deleting a Roster Item

   At contact's status regarding
       presence broadcast (i.e., it SHOULD include the contact's JID in
       any time, a user MAY delete an item from its roster subsequent presence broadcasts initiated by doing an IQ
   set and making sure that the value of user).

   2.  If the 'subscription' attribute user sends directed presence to an entity that is
   "remove" (a compliant server MUST ignore any other values of not in
       the
   'subscription' attribute when received from a client).

   Example: Client removes an item:

   <iq type='set' id='roster_4'>
     <query xmlns='jabber:iq:roster'>
       <item jid='nurse@example.com' subscription='remove'/>
     </query>
   </iq>

   As with adding a user's roster item, when deleting with a roster item subscription type of "from" or "both"
       after having sent initial presence and before sending unavailable
       presence broadcast, the user's server MUST update route or deliver the roster information in persistent storage, initiate a
   "roster push" to all
       full XML of the user's available resources that have
   requested presence stanza to the roster (with entity but MUST NOT
       modify the 'subscription' attribute set to a
   value of "remove"), and send an IQ result to the initiating resource.

   For further information about contact's status regarding available presence
       broadcast (i.e., it MUST NOT include the implications of this command, see
   Section 7.6.




























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7. Integration of Roster Items and Presence Subscriptions

7.1 Overview

   Some level entity's JID in any
       subsequent broadcasts of integration between roster items and available presence
   subscriptions is normally expected initiated by an instant messaging user
   regarding the user's subscriptions to and from other contacts. This
   section describes
       user); however, if the level of integration that must be supported
   within XMPP IM.

   There are four primary subscription states:

   o  None -- Neither connected resource from which the user nor the contact is subscribed to
       sent the
      other's directed presence

   o  To -- The user is subscribed to become unavailable, the contact's user's server
       MUST broadcast that unavailable presence but there
      is no subscription from the contact to the user

   o  From -- There is a subscription from the contact to the user, but entity (if the
       user has not subscribed yet sent directed unavailable presence to that
       entity).

   3.  If the contact's user sends directed presence

   o  Both -- Both without first sending initial
       presence or after having sent unavailable presence broadcast, the user and
       user's server MUST treat the contact are subscribed entities to each
      other's presence (i.e., which the union of 'from' and 'to')

   Each of these states is reflected user sends
       directed presence in the roster of both the user and same way that it treats the contact, thus resulting entities
       listed in durable subscription states. Narrative
   explanations of how these subscription states interact with roster
   items in order to complete certain defined use cases are provided in
   the following sub-sections. Full details regarding server and Case 2 above.

   Before ending its session with a server, a client
   handling of all subscription states (including pending states between
   the primary states listed above) is provided in Section 8.

   If SHOULD gracefully
   become unavailable by sending a connected resource does not both send initial final presence stanza that possesses
   no 'to' attribute and
   request that possesses a 'type' attribute whose value
   is "unavailable" (optionally, the roster, final presence stanza MAY contain
   one or more <status/> elements specifying the reason why the user is
   no longer available). However, the user's server SHOULD MUST NOT send it depend on
   receiving final presence
   subscription requests or "roster pushes".

   The 'from' and 'to' addresess are OPTIONAL in roster pushes; if
   included, their values SHOULD be the full JID of from an available resource, since the
   resource for may become unavailable unexpectedly. If the user's server
   detects that session. A client MUST acknowledge each "roster push" with an IQ
   stanza one of type "result" (for the sake of brevity, these stanzas user's resources has become unavailable for
   any reason (either gracefully or ungracefully), it MUST broadcast
   unavailable presence to all contacts (1) that are
   not shown in the following examples but are required by XMPP Core
   [1]).

7.2 User Subscribes to Contact

   The process by which user's
   roster with a user subscribes subscription type of "from" or "both", (2) to a contact, including whom the
   interaction between roster items
   user has not blocked outbound presence, and subscription states, is defined
   below.



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   1.  In preparation for being able to render (3) from whom the contact in server
   has not received a presence error during the user's
       client interface and for session; the
   user's server MUST also send that unavailable presence stanza to keep track of any
   entities to which the
       subscription, user has sent directed presence during the
   user's client SHOULD perform a "roster set" session for
       the new roster item. This request consists of an IQ stanza of
       type='set' containing a <query/> element in the
       'jabber:iq:roster' namespace, which in turn contains an <item/>
       element that defines the new roster item; resource (if the <item/> element
       MUST possess a 'jid' attribute, MAY possess a 'name' attribute,
       MUST NOT possess a 'subscription' attribute, user has not yet sent
   directed unavailable presence to that entity). Any presence stanza
   with no 'type' attribute and MAY contain one no 'to' attribute that is sent after



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   sending directed unavailable presence or more <group/> child elements:

   <iq type='set' id='int1'>
     <query xmlns='jabber:iq:roster'>
       <item
           jid='contact@otherdomain'
           name='MyContact'>
         <group>MyBuddies</group>
       </item>
     </query>
   </iq>

   2.  As a result, the user's server (1) broadcasted unavailable
   presence MUST initiate a "roster push"
       for be broadcasted by the new roster item server to all available resources associated
       with this user that have requested subscribers.

5.2 Specifying Availability Status

   A client MAY provide further information about its availability
   status by using the roster, setting <show/> element.

   Example: Availability status:

   <presence>
     <show>dnd</show>
   </presence>

   If no <show/> element is provided, the
       'subscription' attribute entity is assumed to a value of "none"; be online
   and (2) MUST reply
       with an IQ stanza of type='result':

   <iq type='set'>
     <query xmlns='jabber:iq:roster'>
       <item
           jid='contact@otherdomain'
           subscription='none'
           name='MyContact'>
         <group>MyBuddies</group>
       </item>
     </query>
   </iq>

   <iq type='result' id='int1'/>

   3.  If available.

5.3 Specifying Detailed Status Information

   In conjunction with the user wants to request  <show/> element, a subscription to client MAY provide
   detailed status information by using the contact's
       presence, <status/> element. The
   content of this element is a natural-language description of the
   user's client MUST send a presence stanza current availability status. The content of
       type='subscribe' to the contact:

   <presence to='contact@otherdomain' type='subscribe'/>

   4.  As a result, status element
   MUST be XML character data and the user's server element MUST initiate a second "roster
       push" to all NOT contain mixed
   content (as defined in Section 3.2.2 of the user's available resources that have XML specification [3]).
   Multiple <status/> elements MAY be included, as long as each such
   element possesses an 'xml:lang' attribute with a distinct value.

   Example: Detailed status information:

   <presence xml:lang='en'>
     <show>dnd</show>
     <status>Wooing Juliet</status>
     <status xml:lang='cz'>Ja dvo&#x0159;&#x00ED;m Juliet</status>
   </presence>


5.4 Specifying Presence Priority

   A client MAY provide a priority for its resource by using the
   <priority/> element (see Priority (Section 2.2.2.3)).

   Example: Presence priority:

   <presence xml:lang='en'>
     <show>dnd</show>
     <status>Wooing Juliet</status>
     <status xml:lang='cz'>Ja dvo&#x0159;&#x00ED;m Juliet</status>



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       requested the roster, setting the contact to the pending
       sub-state of the 'none' subscription state; this pending
       sub-state is denoted by the inclusion of the ask='subscribe'
       attribute


     <priority>1</priority>
   </presence>


5.5 Presence Examples

   The examples in this section illustrate the roster item:

   <iq type='set'>
     <query xmlns='jabber:iq:roster'>
       <item
           jid='contact@otherdomain'
           subscription='none'
           ask='subscribe'
           name='MyContact'>
         <group>MyBuddies</group>
       </item>
     </query>
   </iq>

       Note: if the presence-related
   protocols described above. The user did not create is romeo@example.net, he has
   authorized a roster item before sending the
       subscription request, resource "orchard", and he has the server MUST now create following individuals
   in his roster:

   o  juliet@example.com (subscription="both" and she has two active
      sessions, one whose resource is "chamber" and send a
       "roster push" another whose
      resource is "balcony")

   o  benvolio@example.org (subscription="to")

   o  mercutio@shakespeare.lit (subscription="from")

   Example 1: User sends initial presence:

   <presence/>

   Example 2: User's server sends presence probe to all contacts with
   subscription="to" and subscription="both" on behalf of the user's available resources that have
       requested the roster, absent the 'name' attribute
   connected resource:

   <presence
       type='probe'
       from='romeo@example.net/orchard'
       to='juliet@example.com'/>

   <presence
       type='probe'
       from='romeo@example.net/orchard'
       to='benvolio@example.org'/>

   Example 3: User's server sends initial presence to contacts with
   subscription="from" and subscription="both" on behalf of the <group/
       > child.

   5.  The user's
   connected resource:

   <presence
       from='romeo@example.net/orchard'
       to='juliet@example.com'/>

   <presence
       from='romeo@example.net/orchard'
       to='mercutio@shakespeare.lit'/>



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   Example 4: Contacts' server MUST also stamp the replies to presence stanza probe on behalf of
   all of type
       "subscribe" with the user's bare JID (i.e., <user@somedomain>) as
       the 'from' address. If the contact is served by a different host
       than the user, the user's contact's available resources:

   <presence
       from='juliet@example.com/balcony'
       to='romeo@example.net/orchard'
       xml:lang='en'>
     <show>away</show>
     <status>be right back</status>
     <priority>0</priority>
   </presence>

   <presence
       from='juliet@example.com/chamber'
       to='romeo@example.net/orchard'>
     <priority>1</priority>
   </presence>

   <presence
       from='benvolio@example.org/pda'
       to='romeo@example.net/orchard'
       xml:lang='en'>
     <show>dnd</show>
     <status>gallivanting</status>
   </presence>

   Example 5: Contact's server MUST route the delivers user's initial presence stanza to all
   of the contact's server for delivery available resources or returns error to the contact (this case is
       assumed throughout; however, if the contact is served by the same
       host, then the server can simply deliver the presence stanza
       directly): user:

   <presence
       from='user@somedomain'
       to='contact@otherdomain'
       type='subscribe'/>

   6.  Upon receiving the presence stanza of type "subscribe" addressed
       from='romeo@example.net/orchard'
       to='juliet@example.com/chamber'/>

   <presence
       from='romeo@example.net/orchard'
       to='juliet@example.com/balcony'/>

   <presence
       type='error'
       from='mercutio@shakespeare.lit'
       to='romeo@example.net/orchard'>
     <error type='cancel'>
       <remote-server-not-found
           xmlns='urn:ietf:params:xml:ns:xmpp-stanzas'/>
     </error>
   </presence>





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   Example 6: User sends directed presence to the contact, the contact's server must determine if there is
       at least one active session another user not in which the contact has sent his
   roster:

   <presence
       from='romeo@example.net/orchard'
       to='nurse@example.com'
       xml:lang='en'>
     <show>dnd</show>
     <status>courting Juliet</status>
     <priority>0</priority>
   </presence>

   Example 7: User sends updated available presence and has requested the roster. If so, it MUST
       deliver the subscription request to the contact (if not, the
       contact's server MUST store the subscription request offline information for
       delivery when this condition is next met). No matter when the
       subscription request
   broadcasting:

   <presence xml:lang='en'>
     <show>away</show>
     <status>I shall return!</status>
     <priority>1</priority>
   </presence>

   Example 8: Updated presence information is delivered, the contact must decide
       whether or not to approve it (subject delivered only to configured preferences,
       the contact's client MAY approve one
   contact (not those from whom an error was received or refuse the subscription
       request without presenting it to whom the contact). Here we assume
   user sent directed presence):

   <presence
       from='romeo@example.net/orchard'
       to='juliet@example.com/chamber'
       xml:lang='en'>
     <show>away</show>
     <status>I shall return!</status>
     <priority>1</priority>
   </presence>

   <presence
       from='romeo@example.net/orchard'
       to='juliet@example.com/balcony'
       xml:lang='en'>
     <show>away</show>
     <status>I shall return!</status>
     <priority>1</priority>
   </presence>

   Example 9: One of the contact's resources sends final presence:

   <presence type='unavailable'/>





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       "happy path" that the contact approves the subscription request
       (the alternate flow of declining the subscription request is
       defined in Section 7.2.1). In this case, the contact's client (1)
       SHOULD perform a roster set specifying the desired nickname and
       group for the user; and (2) MUST send a


   Example 10: Contact's server sends unavailable presence stanza of type
       "subscribed" to the user in order information
   to approve the subscription
       request.

   <iq type='set'>
     <query xmlns='jabber:iq:roster'>
       <item
           jid='user@somedomain'
           name='SomeUser'>
         <group>SomeGroup</group>
       </item>
     </query>
   </iq> user:

   <presence to='user@somedomain' type='subscribed'/>

   7.  As a result, the contact's server (1) MUST initiate a "roster
       push" to all available resources associated with the contact that
       have requested the roster, containing a roster item for the user
       with the subscription state set to 'from'; (2) MUST route the
       type='unavailable'
       from='juliet@example.com/balcony'
       to='romeo@example.net/orchard'/>

   Example 11: User sends final presence:

   <presence type='unavailable' xml:lang='en'>
     <status>gone home</status>
   </presence>

   Example 12: Unavailable presence stanza of type "subscribed" information is delivered to the user; and (3) MUST
       send available presence from all of the
   contact's available
       resources one remaining resource as well as to the user:

   <iq type='set'>
     <query xmlns='jabber:iq:roster'>
       <item
           jid='user@somedomain'
           subscription='from'
           name='SomeUser'>
         <group>SomeGroup</group>
       </item>
     </query>
   </iq> person to whom the
   user sent directed presence:

   <presence
       from='contact@otherdomain/resource'
       to='user@somedomain'
       type='subscribed'/>
       type='unavailable'
       from='romeo@example.net/orchard'
       to='juliet@example.com/chamber'
       xml:lang='en'>
     <status>gone home</status>
   </presence>

   <presence
       from='contact@otherdomain/resource'
       to='user@somedomain'/>
       from='romeo@example.net/orchard'
       to='nurse@example.com'
       xml:lang='en'>
     <status>gone home</status>
   </presence>



















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   8.  Upon receiving


6. Managing Subscriptions

   In order to protect the presence stanza privacy of type "subscribed" addressed instant messaging users and any
   other entities, presence and availability information is disclosed
   only to other entities that the user, the user's server MUST first verify user has approved. When a user has
   agreed that another entity may view its presence, the contact entity is in said
   to have a subscription to the user's roster with either of presence information. A
   subscription lasts across sessions; indeed, it lasts until the following states: (a)
       subscription='none', ask='subscribe'
   subscriber unsubscribes or (b) subscription='from',
       ask='subscribe'. If the contact is not in subscribee cancels the user's roster with
       either
   previously-granted subscription. Subscriptions are managed within
   XMPP by sending presence stanzas containing specially-defined
   attributes.

   Note: there are important interactions between subscriptions and
   rosters; these are defined under Integration of those states, the user's server MUST silently ignore Roster Items and
   Presence Subscriptions (Section 8), and the reader must refer to that
   section for a complete understanding of presence subscriptions.

6.1 Requesting a Subscription

   A request to subscribe to another entity's presence is made by
   sending a presence stanza of type "subscribed" (i.e., it MUST NOT route
       it to the user, modify the user's roster, or generate "subscribe".

   Example: Sending a roster
       push to the user's available resources). subscription request:

   <presence to='juliet@example.com' type='subscribe'/>

   If the contact subscription request is being sent to another instant
   messaging user, the JID supplied in the
       user's roster with either 'to' attribute SHOULD be of those states,
   the form <contact@otherdomain> rather than <contact@otherdomain/
   resource>.

   A user's server (1) MUST deliver the presence stanza of type "subscribed" from the
       contact to NOT automatically approve subscription requests
   on the user; (2) user's behalf. All subscription requests MUST initiate a "roster push" be directed to all of
   the user's client. If there is no available resources that have requested the roster,
       containing an updated roster item for the contact resource associated with
   the
       'subscription' attribute set to a value of "to"; and (3) MUST
       deliver user when the available presence stanza subscription request is received from each of by the
       contact's available resources to each of server, the
   user's available
       resources:

   <presence
       to='user@somedomain'
       from='contact@otherdomain'
       type='subscribed'/>

   <iq type='set'>
     <query xmlns='jabber:iq:roster'>
       <item
           jid='contact@otherdomain'
           subscription='to'
           name='MyContact'>
         <group>MyBuddies</group>
       </item>
     </query>
   </iq>

   <presence
       from='contact@otherdomain/resource'
       to='user@somedomain/resource'/>

   9.  Upon receiving server MUST store the presence stanza of type "subscribed", subscription request offline for
   delivery when the user next becomes available. (Note: if a resource
   has authorized a session but has not provided initial presence, the
   server SHOULD acknowledge receipt of that NOT consider it to be available and therefore SHOULD
   NOT send subscription state
       notification through either "affirming" requests to it.)

6.2 Handling a Subscription Request

   When a client receives a subscription request from another entity, it
   MUST either approve the request by sending a presence stanza of type "subscribe" to the contact
   "subscribed" or "denying" it refuse the request by sending a presence stanza of
   type "unsubscribe" to the contact;
       this step does not necessarily affect the subscription state (see
       Section 8 for details), but instead lets the user's server know
       that it must no longer send notification of the subscription
       state change to the user (see Section 8.6). "unsubscribed".



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   From the perspective of the user, there now exists


   Example: Approving a subscription to
   the contact; from the perspective of the contact, there now exists request:

   <presence to='romeo@example.net' type='subscribed'/>

   Example: Refusing a presence subscription request:

   <presence to='romeo@example.net' type='unsubscribed'/>


6.3 Cancelling a Subscription from the user. (Note: Another Entity

   If at this point the a user would like to cancel a previously-granted subscription
   request, it sends
   another a presence stanza of type "unsubscribed".

   Example: Cancelling a previously granted subscription request to the contact, the user's server MUST
   silently ignore that request.)

7.2.1 Alternate Flow: Contact Declines Subscription Request

   The above activity flow represents the "happy path" related request:

   <presence to='romeo@example.net' type='unsubscribed'/>


6.4 Unsubscribing from Another Entity's Presence

   If a user would like to the
   user's subscription request to the contact. The main alternate flow
   occurs if the contact refuses the user's subscription request.

   1.  If the contact wants to refuse the request, the contact's client
       MUST send a presence stanza of type "unsubscribed" to the user
       (instead of unsubscribe from the presence stanza of type "subscribed" sent in Step
       6 of Section 7.2):

   <presence to='user@somedomain' type='unsubscribed'/>

   2.  As another
   entity, it sends a result, the contact's server MUST route the presence stanza
       of type "unsubscribed" to the user, first stamping the 'from'
       address as the bare JID (<contact@otherdomain>) of the contact:

   <presence
       from='contact@otherdomain'
       to='user@somedomain'
       type='unsubscribed'/>

   3.  Upon receiving the presence stanza of type "unsubscribed"
       addressed to the user, the user's server (1) MUST deliver that
       presence stanza to the user and (2) MUST initiate a "roster push"
       to all of the user's available resources that have requested the
       roster, containing "unsubscribe".

   Example: Unsubscribing from an updated roster item for the contact with
       the 'subscription' attribute set to a value of "none" and with no
       'ask' attribute: entity's presence:

   <presence
       from='contact@otherdomain'
       to='user@somedomain'
       type='unsubscribed'/>

   <iq type='set'>
     <query xmlns='jabber:iq:roster'>
       <item
           jid='contact@otherdomain'
           subscription='none'
           name='MyContact'>
         <group>MyBuddies</group> to='juliet@example.com' type='unsubscribe'/>
























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       </item>
     </query>
   </iq>

   4.  Upon receiving the presence stanza


7. Roster Management

   In XMPP, one's contact list is called a roster, which consists of type "unsubscribed", the
       user SHOULD acknowledge receipt any
   number of that subscription state
       notification through either "affirming" it specific roster items, each roster item being identified by sending
   a presence
       stanza unique JID (usually of type "unsubscribe" to the contact or "denying" it form <contact@otherdomain>). A user's
   roster is stored by
       sending a presence stanza of type "subscribe" to the contact;
       this step does not necessarily affect the subscription state (see
       Section 8 for details), but instead lets the user's server know on the user's behalf so that it must no longer send notification
   the user may access roster information from any available resource.

   Note: there are important interactions between rosters and
   subscriptions; these are defined under Integration of Roster Items
   and Presence Subscriptions (Section 8), and the subscription
       state change reader must refer to the user (see Section 8.6).

   As
   that section for a result complete understanding of this activity, roster management.

7.1 Syntax and Semantics

   Rosters are managed using IQ stanzas, specifically by means of a
   <query/> child element qualified by the contact 'jabber:iq:roster' namespace.
   The <query/> element may contain one or more <item/> children, each
   describing a unique roster item or "contact".

   The "key" or unique identifier for each roster item is now a JID,
   encapsulated in the user's roster required 'jid' attribute of the <item/> element.
   The value of the 'jid' attribute SHOULD be of the form
   <user@somedomain>, especially if the item is associated with a subscription another
   (human) instant messaging user.

   The state of "none", whereas the user presence subscription in relation to to a roster
   item is not captured in the
   contact's roster at all.

7.3 Creating a Mutual Subscription

   The user and contact can build on 'subscription' attribute of the foregoing to create a mutual
   subscription (i.e., <item/>
   element. Allowable values for this attribute are "none" (the user
   does not have a subscription of type "both"). The process is
   defined below.

   1.  If the contact wants to create a mutual subscription, the contact, and the contact
       MUST send does not
   have a subscription request to the user), "to" (the user (subject has a subscription
   to
       configured preferences, the contact's client MAY send this
       automatically):

   <presence to='user@somedomain' type='subscribe'/>

   2.  As a result, contact, but the contact's server (1) MUST initiate contact does not have a "roster
       push" subscription to all available resources associated with the
   user), "from" (the contact that has a subscription to the user, but the
   user does not have requested a subscription to the roster, with contact), and "both" (both
   the user still in and the 'from'
       subscription state but with contact have subscriptions to each other).

   Each <item/> element MAY contain a pending 'to' subscription denoted 'name' attribute, which sets the
   "nickname" to be associated with the JID, as determined by the inclusion user
   (not the contact). The value of the ask='subscribe' 'name' attribute is opaque.

   Each <item/> element MAY contain one or more <group/> child elements,
   for use in categorizing JIDs in various "buckets". The CDATA text of
   the <group/> element is opaque.

7.2 Business Rules

   A server MUST ignore any 'to' address on a roster
       item; "set", and (2) MUST route the presence stanza of type "subscribe"
       to the user, first stamping the 'from' address
   treat any roster "set" as applying to the bare JID
       (<contact@otherdomain>) of the contact:

   <iq type='set'>
     <query xmlns='jabber:iq:roster'>
       <item
           jid='user@somedomain'
           subscription='from'
           ask='subscribe'
           name='SomeUser'>
         <group>SomeGroup</group> sender. For added safety, a



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       </item>
     </query>
   </iq>

   <presence
       from='contact@otherdomain'
       to='user@somedomain'
       type='subscribe'/>

   3.  Upon receiving


   client SHOULD check the presence stanza "from" address of type "subscribe" addressed a roster "push" to ensure
   that it is from a trusted source; specifically, the user, stanza should
   have no 'from' attribute (i.e., implicitly from the user's server must determine if there is at
       least one active session server) or the
   JID contained in which the user has sent available
       presence and has requested the roster. If so, 'from' attribute should match the user's server
       MUST deliver the subscription request to the user (if not, it
       MUST store the subscription request offline for delivery when
       this condition is next met). No matter when the subscription
       request is delivered, the user must then decide whether bare
   JID or not to
       approve it (subject to configured preferences, full JID; otherwise, the user's client
       MAY approve or refuse SHOULD ignore the subscription request without presenting
       it roster
   "push".

7.3 Retrieving One's Roster on Login

   Upon connecting to the user). Here we assume the "happy path" that the user
       approves the subscription request (the alternate flow of
       declining the subscription request is defined in Section 7.3.1).
       In this case, the user's client MUST send server, a presence stanza of
       type "subscribed" to client SHOULD request the contact in order to approve roster
   (however, because receiving the
       subscription request.

   <presence to='contact@otherdomain' type='subscribed'/>

   4.  As roster may not be desirable for all
   resources, e.g., a result, connection with limited bandwidth, the user's server (1) MUST initiate a "roster push"
       to all of client's
   request for the user's roster is NOT REQUIRED). If an available resources that have requested resource
   does not request the
       roster, containing a roster item for the contact with the
       'subscription' attribute set to during a value of "both"; (2) MUST route
       the presence stanza of type "subscribed" to the contact, first
       stamping the 'from' address as the bare JID (<user@somedomain>)
       of session, the user; and (3) MUST server SHOULD NOT
   send available it presence subscriptions and associated "roster pushes".

   Example: Client requests current roster from each of
       the user's available resources to the contact: server:

   <iq type='set'> type='get' id='roster_1'>
     <query xmlns='jabber:iq:roster'>
       <item
           jid='contact@otherdomain'
           subscription='both'
           name='MyContact'>
         <group>MyBuddies</group> xmlns='jabber:iq:roster'/>
   </iq>

   Example: Client receives roster from the server:

   <iq id='roster_1' type='result'>
     <query xmlns='jabber:iq:roster'>
       <item jid='romeo@example.net'
             name='Romeo'
             subscription='both'>
         <group>Friends</group>
       </item>
       <item jid='mercutio@shakespeare.lit'
             name='Mercutio'
             subscription='from'>
         <group>Friends</group>
       </item>
       <item jid='benvolio@example.org'
             name='Benvolio'
             subscription='both'>
         <group>Friends</group>
       </item>
     </query>
   </iq>


7.4 Adding a Roster Item

   At any time, a user MAY add an item to his or her roster.



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   <presence
       from='user@somedomain'
       to='contact@otherdomain'
       type='subscribed'/>

   <presence
       from='user@somedomain/resource'
       to='contact@otherdomain'/>

   5.  Upon receiving the presence stanza of type "subscribed" addressed
       to the contact, the contact's


   Example: Client adds a new item:

   <iq type='set' id='roster_2'>
     <query xmlns='jabber:iq:roster'>
       <item jid='nurse@example.com'
             name='Nurse'>
         <group>Servants</group>
       </item>
     </query>
   </iq>

   The server MUST first verify that the
       user is in update the contact's roster with either of the following
       states: (a) subscription='none', ask='subscribe' or (b)
       subscription='from', ask='subscribe'. If the user is not information in persistent storage,
   and also push the
       contact's roster with either change out to all of those states, the contact's
       server MUST silently ignore user's available resources
   that have requested the presence stanza roster. This "roster push" consists of type
       "subscribed" (i.e., it MUST NOT route it to the contact, modify an IQ
   set from the contact's roster, or generate a roster push server to the contact's client and enables all available resources). If the user is resources
   to remain in the contact's roster sync with
       either of those states, the contact's server server-based roster information.

   Example: Server (1) MUST deliver the
       presence stanza of type "subscribed" from the user to pushes the
       contact; (2) MUST initiate a "roster push" updated roster information to all
   available resources associated and (2) replies with the contact that have requested the
       roster, containing an updated roster item for IQ result to the user with the
       'subscription' attribute set to a value of "both"; and (3) MUST
       deliver the available presence stanza received from each of the
       user's available resources to each of the contact's available
       resources:

   <presence
       from='user@somedomain'
       to='contact@otherdomain'
       type='subscribed'/> sending
   resource:

   <iq type='set'>
     <query xmlns='jabber:iq:roster'>
       <item
           jid='user@somedomain'
           subscription='both'
           name='SomeUser'>
         <group>SomeGroup</group> jid='nurse@example.com'
             name='Nurse'
             subscription='none'>
         <group>Servants</group>
       </item>
     </query>
   </iq>

   <presence
       from='user@somedomain/resource'
       to='contact@otherdomain/resource'/>

   <iq type='set'>
     <query xmlns='jabber:iq:roster'>
       <item jid='nurse@example.com'
             name='Nurse'
             subscription='none'>
         <group>Servants</group>
       </item>
     </query>
   </iq>

   <iq type='result' id='roster_2'/>

   Example: Connected resources reply with an IQ result to the server:

   <iq from='juliet@example.com/balcony'
       to='example.com'
       type='result'/>



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   6.  Upon receiving


   <iq from='juliet@example.com/chamber'
       to='example.com'
       type='result'/>


7.5 Updating a Roster Item

   Updating an existing roster item (e.g., changing the presence stanza of type "subscribed", group) is done
   in the
       contact SHOULD acknowledge receipt of that subscription state
       notification through either "affirming" it by sending same way as adding a presence
       stanza of type "subscribe" to the user or "denying" it new roster item, i.e., by sending
       a presence stanza of type "unsubscribe" to the user; this step
       does not necessarily affect
   roster item in an IQ set to the subscription state (see Section 8
       for details), but instead lets server.

   Example: User updates roster item (added group):

   <iq type='set' id='roster_3'>
     <query xmlns='jabber:iq:roster'>
       <item jid='romeo@example.net'
             name='Romeo'
             subscription='both'>
         <group>Friends</group>
         <group>Lovers</group>
       </item>
     </query>
   </iq>

   As with adding a roster item, when updating a roster item the contact's server know that it
       must no longer send notification of the subscription state change
       to
   MUST update the contact (see Section 8.6).

   The user roster information in persistent storage, and the contact now have also
   initiate a mutual subscription "roster push" to each
   other's presence -- i.e., the subscription is of type "both". The
   user's server MUST now send all of the user's current presence information
   to the contact. (Note: If at this point available resources
   that have requested the user sends roster.

7.6 Deleting a subscription
   request to the contact or the contact sends Roster Item

   At any time, a subscription request to user MAY delete an item from its roster by doing an IQ
   set and making sure that the user, value of the sending user's 'subscription' attribute is
   "remove" (a compliant server MUST silently ignore that request
   and not route it to any other values of the intended recipient.)

7.3.1 Alternate Flow: User Declines Subscription Request

   The above activity flow represents
   'subscription' attribute when received from a client).

   Example: Client removes an item:

   <iq type='set' id='roster_4'>
     <query xmlns='jabber:iq:roster'>
       <item jid='nurse@example.com' subscription='remove'/>
     </query>
   </iq>

   As with adding a roster item, when deleting a roster item the "happy path" related to server
   MUST update the
   contact's subscription request roster information in persistent storage, initiate a
   "roster push" to all of the user. The main alternate flow
   occurs if the user refuses user's available resources that have
   requested the contact's subscription request.

   1.  If roster (with the user wants 'subscription' attribute set to refuse the request, the user's client MUST
       send a presence stanza



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   value of type "unsubscribed" "remove"), and send an IQ result to the contact
       (instead of initiating resource.

   For further information about the presence stanza of type "subscribed" sent in Step
       3 implications of Section 7.3):

   <presence to='contact@otherdomain' type='unsubscribed'/>

   2.  As this command, see
   Removing a result, the user's server MUST route the presence stanza Roster Item and Cancelling All Subscriptions (Section
   8.6).














































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8. Integration of
       type "unsubscribed" to the contact, first stamping Roster Items and Presence Subscriptions

8.1 Overview

   Some level of integration between roster items and presence
   subscriptions is normally expected by an instant messaging user
   regarding the 'from'
       address as user's subscriptions to and from other contacts. This
   section describes the bare JID (<user@somedomain>) level of integration that must be supported
   within XMPP IM.

   There are four primary subscription states:

   o  None -- Neither the user:

   <presence
       from='user@somedomain'
       to='contact@otherdomain'
       type='unsubscribed'/>

   3.  Upon receiving user nor the presence stanza of type "unsubscribed"
       addressed contact is subscribed to the contact,
      other's presence

   o  To -- The user is subscribed to the contact's server (1) MUST deliver
       that presence stanza but there
      is no subscription from the contact to the contact; and (2) MUST initiate user

   o  From -- There is a
       "roster push" to all available resources associated with subscription from the contact that have requested to the roster, containing an updated
       roster item for user, but
      the user with the 'subscription' attribute set has not subscribed to
       a value of "from" and with no 'ask' attribute:




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   <presence
       from='user@somedomain'
       to='contact@otherdomain'
       type='unsubscribed'/>

   <iq type='set'>
     <query xmlns='jabber:iq:roster'>
       <item
           jid='user@somedomain'
           subscription='from'
           name='SomeUser'>
         <group>SomeGroup</group>
       </item>
     </query>
   </iq>

   4.  Upon receiving the contact's presence stanza of type "unsubscribed",

   o  Both -- Both the user and the contact SHOULD acknowledge receipt of that subscription state
       notification through either "affirming" it by sending a are subscribed to each
      other's presence
       stanza (i.e., the union of type "unsubscribe" to 'from' and 'to')

   Each of these states is reflected in the user or "denying" it by
       sending a presence stanza roster of type "subscribe" to both the user; this
       step does not necessarily affect user and
   the contact, thus resulting in durable subscription state (see
       Section 8 for details), but instead lets the contact's server
       know that it must no longer send notification states. Narrative
   explanations of the how these subscription
       state change states interact with roster
   items in order to the contact (see Section 8.6).

   As a result of this activity, there has been no change complete certain defined use cases are provided in
   the following sub-sections. Full details regarding server and client
   handling of all subscription state; i.e., states (including pending states between
   the contact primary states listed above) is provided in the user's roster with Subscription States
   (Section 9).

   If a
   subscription state of "to" connected resource does not both send initial presence and
   request the user is in roster, the contact's roster
   with a server SHOULD NOT send it presence
   subscription state requests or "roster pushes".

   The 'from' and 'to' addresess are OPTIONAL in roster pushes; if
   included, their values SHOULD be the full JID of "from".

7.4 Unsubscribing

   At any time after subscribing to a contact's presence, a user MAY
   unsubscribe. While the XML resource for
   that session. A client MUST acknowledge each "roster push" with an IQ
   stanza of type "result" (for the sake of brevity, these stanzas are
   not shown in the following examples but are required by XMPP Core
   [1]).

8.2 User Subscribes to Contact

   The process by which a user sends subscribes to make this happen is a contact, including the same in all instances, the subsequent
   interaction between roster items and subscription state states, is
   different depending on the subscription state obtaining when the
   unsubscribe "command" was sent. Both possible scenarios are defined



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   below.

7.4.1 Case #1: Unsubscribing When Subscription is Not Mutual

   1.  In the first case, the user has a subscription preparation for being able to render the contact but the
   contact does not have a subscription to the user (i.e., in the
   subscription is not yet mutual).

   1.  If user's
       client interface and for the user wants server to unsubscribe from keep track of the contact's presence,
       subscription, the
       user MUST send user's client SHOULD perform a presence "roster set" for
       the new roster item. This request consists of an IQ stanza of type "unsubscribe" to
       type='set' containing a <query/> element in the



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       contact:

   <presence to='contact@otherdomain' type='unsubscribe'/>
       'jabber:iq:roster' namespace, which in turn contains an <item/>
       element that defines the new roster item; the <item/> element
       MUST possess a 'jid' attribute, MAY possess a 'name' attribute,
       MUST NOT possess a 'subscription' attribute, and MAY contain one
       or more <group/> child elements:

   <iq type='set' id='int1'>
     <query xmlns='jabber:iq:roster'>
       <item
           jid='contact@otherdomain'
           name='MyContact'>
         <group>MyBuddies</group>
       </item>
     </query>
   </iq>

   2.  As a result, the user's server (1) MUST send initiate a "roster push"
       for the new roster item to all of the user's available resources associated
       with this user that have requested the roster, containing an updated roster item for the contact with setting the
       'subscription' attribute set to a value of "none"; and (2) MUST route the presence reply
       with an IQ stanza of type "unsubscribe" to the
       contact, first stamping the 'from' address as the bare JID
       (<user@somedomain>) of the user: type='result':

   <iq type='set'>
     <query xmlns='jabber:iq:roster'>
       <item
           jid='contact@otherdomain'
           subscription='none'
           name='MyContact'>
         <group>MyBuddies</group>
       </item>
     </query>
   </iq>

   <presence
       from='user@somedomain'
       to='contact@otherdomain'
       type='unsubscribe'/>

   <iq type='result' id='int1'/>

   3.  Upon receiving  If the user wants to request a subscription to the contact's
       presence, the user's client MUST send a presence stanza of type "unsubscribe"
       addressed
       type='subscribe' to the contact, contact:

   <presence to='contact@otherdomain' type='subscribe'/>




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   4.  As a result, the contact's user's server (1) MUST initiate a second "roster
       push" to all of the user's available resources associated with the
       contact that have
       requested the roster, containing an updated
       roster item for the user with setting the 'subscription' attribute set contact to
       a value the pending
       sub-state of "none" (if the contact 'none' subscription state; this pending
       sub-state is offline, the contact's
       server MUST modify the roster item and send that modified item
       the next time the contact requests denoted by the roster); and (2) MUST
       deliver inclusion of the "unsubscribe" state change notification to ask='subscribe'
       attribute in the
       contact: roster item:

   <iq type='set'>
     <query xmlns='jabber:iq:roster'>
       <item
           jid='user@somedomain'
           jid='contact@otherdomain'
           subscription='none'
           name='SomeUser'>
         <group>SomeGroup</group>
           ask='subscribe'
           name='MyContact'>
         <group>MyBuddies</group>
       </item>
     </query>



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   </iq>

   <presence
       from='user@somedomain'
       to='contact@otherdomain'
       type='unsubscribe'/>

   4.  Upon receiving the presence stanza of type "unsubscribe", the
       contact SHOULD acknowledge receipt of that subscription state
       notification through either "affirming" it by sending a presence
       stanza of type "unsubscribed" to

       Note: if the user or "denying" it by
       sending a presence stanza of type "subscribed" to the user; this
       step does did not necessarily affect create a roster item before sending the
       subscription state (see
       Section 8 for details), but instead lets request, the contact's server
       know that it must no longer MUST now create one and send notification a
       "roster push" to all of the subscription
       state change to user's available resources that have
       requested the contact (see Section 8.6). roster, absent the 'name' attribute and the <group/
       > child.

   5.  The contact's user's server then (1) MUST send a also stamp the presence stanza of type
       "unsubscribed" to
       "subscribe" with the user; and (2) SHOULD send unavailable
       presence from user's bare JID (i.e., <user@somedomain>) as
       the 'from' address. If the contact to is served by a different host
       than the user:

   <presence
       from='contact@otherdomain'
       to='user@somedomain'
       type='unsubscribed'/>

   <presence
       from='contact@otherdomain'
       to='user@somedomain'
       type='unavailable'/>

   6.  When user, the user's server receives a MUST route the presence stanza of type
       "unsubscribed" and/or unavailable presence, it MUST deliver them
       to the user:

   <presence
       from='contact@otherdomain'
       to='user@somedomain'
       type='unsubscribed'/> contact's server for delivery to the contact (this case is
       assumed throughout; however, if the contact is served by the same
       host, then the server can simply deliver the presence stanza
       directly):

   <presence
       from='contact@otherdomain'
       to='user@somedomain'
       type='unavailable'/>

   7.
       from='user@somedomain'
       to='contact@otherdomain'
       type='subscribe'/>

   6.  Upon receiving the presence stanza of type "unsubscribed", "subscribe" addressed
       to the contact, the contact's server must determine if there is
       at least one active session in which the contact has sent
       available presence and has requested the roster. If so, it MUST
       deliver the
       user SHOULD acknowledge receipt of that subscription state
       notification through either "affirming" request to the contact (if not, the
       contact's server MUST store the subscription request offline for
       delivery when this condition is next met). No matter when the
       subscription request is delivered, the contact must decide
       whether or not to approve it by sending a presence (subject to configured preferences,



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       stanza of type "unsubscribe" to


       the contact contact's client MAY approve or "denying" refuse the subscription
       request without presenting it by
       sending a presence stanza of type "subscribe" to the contact;
       this step does not necessarily affect the subscription state (see
       Section 8 for details), but instead lets contact). Here we assume the user's server know
       "happy path" that it must no longer send notification of the contact approves the subscription
       state change to request
       (the alternate flow of declining the user (see Section 8.6).


7.4.2 Case #2: Unsubscribing When Subscription subscription request is Mutual
       defined in Section 8.2.1). In the second this case, the user has contact's client (1)
       SHOULD perform a subscription to roster set specifying the contact desired nickname and
       group for the contact also has a subscription to the user (i.e., the
   subscription is mutual).

   1.  If the user wants to unsubscribe from the contact's presence, the
       user user; and (2) MUST send a presence stanza of type "unsubscribe"
       "subscribed" to the
       contact: user in order to approve the subscription
       request.

   <iq type='set'>
     <query xmlns='jabber:iq:roster'>
       <item
           jid='user@somedomain'
           name='SomeUser'>
         <group>SomeGroup</group>
       </item>
     </query>
   </iq>

   <presence to='contact@otherdomain' type='unsubscribe'/>

   2. to='user@somedomain' type='subscribed'/>

   7.  As a result, the user's contact's server (1) MUST send initiate a "roster
       push" to all of the user's available resources associated with the contact that
       have requested the roster, containing an updated a roster item for the contact user
       with the 'subscription' attribute subscription state set to a value of "from"; and 'from'; (2) MUST route the
       presence stanza of type "unsubscribe" "subscribed" to the
       contact, first stamping the 'from' address as the bare JID
       (<user@somedomain>) user; and (3) MUST
       send available presence from all of the contact's available
       resources to the user:

   <iq type='set'>
     <query xmlns='jabber:iq:roster'>
       <item
           jid='contact@otherdomain'
           jid='user@somedomain'
           subscription='from'
           name='MyContact'>
         <group>MyBuddies</group>
           name='SomeUser'>
         <group>SomeGroup</group>
       </item>
     </query>
   </iq>

   <presence
       from='user@somedomain'
       to='contact@otherdomain'
       type='unsubscribe'/>

   3.
       from='contact@otherdomain/resource'
       to='user@somedomain'
       type='subscribed'/>

   <presence
       from='contact@otherdomain/resource'



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       to='user@somedomain'/>

   8.  Upon receiving the presence stanza of type "unsubscribe" "subscribed" addressed
       to the contact, user, the contact's user's server (1) MUST initiate
       a "roster push" to all available resources associated with first verify that the contact that have requested
       is in the roster, containing an updated



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Internet-Draft           XMPP Instant Messaging              August 2003 user's roster item for with either of the user following states: (a)
       subscription='none', ask='subscribe' or (b) subscription='from',
       ask='subscribe'. If the contact is not in the user's roster with
       either of those states, the 'subscription' attribute set user's server MUST silently ignore
       the presence stanza of type "subscribed" (i.e., it MUST NOT route
       it to the user, modify the user's roster, or generate a value of "to" (if roster
       push to the user's available resources). If the contact is offline, in the contact's
       user's roster with either of those states, the user's server (1)
       MUST modify deliver the roster item and send presence stanza of type "subscribed" from the
       contact to the user; (2) MUST initiate a "roster push" to all of
       the user's available resources that modified item have requested the next
       time roster,
       containing an updated roster item for the contact requests with the roster);
       'subscription' attribute set to a value of "to"; and (2) (3) MUST
       deliver the
       "unsubscribe" state change notification available presence stanza received from each of the
       contact's available resources to each of the contact: user's available
       resources:

   <presence
       to='user@somedomain'
       from='contact@otherdomain'
       type='subscribed'/>

   <iq type='set'>
     <query xmlns='jabber:iq:roster'>
       <item
           jid='user@somedomain'
           jid='contact@otherdomain'
           subscription='to'
           name='SomeUser'>
         <group>SomeGroup</group>
           name='MyContact'>
         <group>MyBuddies</group>
       </item>
     </query>
   </iq>

   <presence
       from='user@somedomain'
       to='contact@otherdomain'
       type='unsubscribe'/>

   4.
       from='contact@otherdomain/resource'
       to='user@somedomain/resource'/>

   9.  Upon receiving the presence stanza of type "unsubscribe", "subscribed", the
       contact user
       SHOULD acknowledge receipt of that subscription state
       notification through either "affirming" it by sending a presence
       stanza of type "unsubscribed" "subscribe" to the user contact or "denying" it by
       sending a presence stanza of type "subscribed" "unsubscribe" to the user; contact;
       this step does not necessarily affect the subscription state (see
       Section 8
       Subscription States (Section 9) for details), but instead lets



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       the contact's user's server know that it must no longer send notification
       of the subscription state change to the contact user (see Section 8.6).

   5.  The contact's server then (1) MUST send a presence stanza 9.6).

   From the perspective of type
       "unsubscribed" the user, there now exists a subscription to
   the user; and (2) SHOULD send unavailable
       presence contact; from the contact to perspective of the user:

   <presence
       from='contact@otherdomain'
       to='user@somedomain' contact, there now exists a
   subscription from the user. (Note: If at this point the user sends
   another subscription request to the contact, the user's server MUST
   silently ignore that request.)

8.2.1 Alternate Flow: Contact Declines Subscription Request

   The above activity flow represents the "happy path" related to the
   user's subscription request to the contact. The main alternate flow
   occurs if the contact refuses the user's subscription request.

   1.  If the contact wants to refuse the request, the contact's client
       MUST send a presence stanza of type "unsubscribed" to the user
       (instead of the presence stanza of type "subscribed" sent in Step
       6 of Section 8.2):

   <presence to='user@somedomain' type='unsubscribed'/>

   2.  As a result, the contact's server MUST route the presence stanza
       of type "unsubscribed" to the user, first stamping the 'from'
       address as the bare JID (<contact@otherdomain>) of the contact:

   <presence
       from='contact@otherdomain'
       to='user@somedomain'
       type='unavailable'/>

   6.  When
       type='unsubscribed'/>

   3.  Upon receiving the user's server receives a presence stanza of type "unsubscribed" and/or unavailable presence, it
       addressed to the user, the user's server (1) MUST deliver them that
       presence stanza to the user and (2) MUST initiate a "roster push"
       to all of the user's available resources that have requested the
       roster, containing an updated roster item for the contact with
       the 'subscription' attribute set to a value of "none" and with no
       'ask' attribute:

   <presence
       from='contact@otherdomain'
       to='user@somedomain'
       type='unsubscribed'/>

   <iq type='set'>
     <query xmlns='jabber:iq:roster'>
       <item
           jid='contact@otherdomain'



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       to the user:

   <presence
       from='contact@otherdomain'
       to='user@somedomain'
       type='unsubscribed'/>

   <presence
       from='contact@otherdomain'
       to='user@somedomain'
       type='unavailable'/>

   7.


           subscription='none'
           name='MyContact'>
         <group>MyBuddies</group>
       </item>
     </query>
   </iq>

   4.  Upon receiving the presence stanza of type "unsubscribed", the
       user SHOULD acknowledge receipt of that subscription state
       notification through either "affirming" it by sending a presence
       stanza of type "unsubscribe" to the contact or "denying" it by
       sending a presence stanza of type "subscribe" to the contact;
       this step does not necessarily affect the subscription state (see
       Section 8
       Subscription States (Section 9) for details), but instead lets
       the user's server know that it must no longer send notification
       of the subscription state change to the user (see Section 8.6).

   Note: Obviously this does not 9.6).

   As a result in removal of the roster item
   from the user's roster, and this activity, the contact still has a subscription to
   the user's presence. In order to both completely cancel a mutual
   subscription and fully remove the roster item from is now in the user's roster,
   the user should update the roster item
   with subscription='remove' as
   defined in Section 7.6.

7.5 Cancelling a Subscription

   At any time after approving a subscription request from a user, a
   contact MAY cancel that subscription. While the XML that state of "none", whereas the contact
   sends to make this happen user is the same not in all instances, the
   subsequent subscription state is different depending on the
   subscription state obtaining when the cancellation was sent. Both
   possible scenarios are defined below.

7.5.1 Case #1: Cancelling When Subscription is Not
   contact's roster at all.

8.3 Creating a Mutual

   In the first case, the Subscription

   The user has a subscription to the and contact but can build on the
   contact does not have foregoing to create a mutual
   subscription to the user (i.e., the a subscription of type "both"). The process is not yet mutual).
   defined below.

   1.  If the contact wants to cancel the user's create a mutual subscription, the contact
       MUST send a presence stanza of type "unsubscribed" subscription request to the
       user:




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       configured preferences, the contact's client MAY send this
       automatically):

   <presence to='user@somedomain' type='unsubscribed'/> type='subscribe'/>

   2.  As a result, the contact's server (1) MUST send initiate a "roster
       push" to all of the contact's available resources associated with the contact that
       have requested the roster, containing an updated roster item for with the user with still in the 'subscription' attribute set to 'from'
       subscription state but with a value pending 'to' subscription denoted
       by the inclusion of "none"; the ask='subscribe' attribute in the roster
       item; and (2) MUST route the presence stanza of type "unsubscribed" "subscribe"
       to the user, first stamping the 'from' address as the bare JID
       (<contact@otherdomain>) of the contact; and (3) SHOULD send
       unavailable presence from the contact to the user: contact:

   <iq type='set'>
     <query xmlns='jabber:iq:roster'>
       <item
           jid='user@somedomain'
           subscription='none'
           subscription='from'



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           ask='subscribe'
           name='SomeUser'>
         <group>SomeGroup</group>
       </item>
     </query>
   </iq>

   <presence
       from='contact@otherdomain'
       to='user@somedomain'
       type='unsubscribed'/>

   <presence
       from='contact@otherdomain'
       to='user@somedomain'
       type='unavailable'/>
       type='subscribe'/>

   3.  Upon receiving the presence stanza of type "unsubscribed" "subscribe" addressed
       to the user, the user's server must determine if there is at
       least one active session in which the user has sent available
       presence and has requested the roster. If so, the user's server
       MUST deliver the subscription request to the user (if not, it
       MUST store the subscription request offline for delivery when
       this condition is next met). No matter when the subscription
       request is delivered, the user must then decide whether or not to
       approve it (subject to configured preferences, the user's client
       MAY approve or refuse the subscription request without presenting
       it to the user). Here we assume the "happy path" that the user
       approves the subscription request (the alternate flow of
       declining the subscription request is defined in Section 8.3.1).
       In this case, the user's client MUST send a presence stanza of
       type "subscribed" to the contact in order to approve the
       subscription request.

   <presence to='contact@otherdomain' type='subscribed'/>

   4.  As a result, the user's server (1) MUST initiate a "roster push"
       to all of the user's available resources that have requested the
       roster, containing an updated a roster item for the contact with the
       'subscription' attribute set to a value of
       "none" (if the user is offline, the user's server "both"; (2) MUST modify the
       roster item and send that modified item route
       the next time presence stanza of type "subscribed" to the user
       requests contact, first
       stamping the roster); (2) MUST deliver 'from' address as the "unsubscribed" state
       change notification to bare JID (<user@somedomain>)
       of the user; and (3) MUST deliver the
       unavailable send available presence to from each of
       the user:

   <iq user's available resources to the contact:

   <iq type='set'>
     <query xmlns='jabber:iq:roster'>
       <item
           jid='contact@otherdomain'
           subscription='none'
           subscription='both'
           name='MyContact'>
         <group>MyBuddies</group>
       </item>



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           name='MyContact'>
         <group>MyBuddies</group>
       </item>


     </query>
   </iq>

   <presence
       from='contact@otherdomain'
       to='user@somedomain'
       type='unsubscribed'/>
       from='user@somedomain'
       to='contact@otherdomain'
       type='subscribed'/>

   <presence
       from='contact@otherdomain'
       to='user@somedomain'
       type='unavailable'/>

   4.
       from='user@somedomain/resource'
       to='contact@otherdomain'/>

   5.  Upon receiving the presence stanza of type "unsubscribed", "subscribed" addressed
       to the
       user SHOULD acknowledge receipt of contact, the contact's server MUST first verify that subscription state
       notification through the
       user is in the contact's roster with either "affirming" it by sending a presence
       stanza of type "unsubscribe" to the contact following
       states: (a) subscription='none', ask='subscribe' or "denying" it by
       sending a presence stanza of type "subscribe" to (b)
       subscription='from', ask='subscribe'. If the contact;
       this step does user is not necessarily affect in the subscription state (see
       Section 8 for details), but instead lets
       contact's roster with either of those states, the user's contact's
       server know
       that it must no longer send notification of MUST silently ignore the subscription
       state change presence stanza of type
       "subscribed" (i.e., it MUST NOT route it to the user (see Section 8.6).


7.5.2 Case #2: Cancelling When Subscription is Mutual

   In the second case, contact, modify
       the user has contact's roster, or generate a subscription roster push to the contact and
   the contact also has a subscription to contact's
       available resources). If the user (i.e., the
   subscription is mutual).

   1.  If the contact wants to cancel in the user's subscription, contact's roster with
       either of those states, the
       contact contact's server (1) MUST send a deliver the
       presence stanza of type "unsubscribed" to "subscribed" from the
       user:

   <presence to='user@somedomain' type='unsubscribed'/>

   2.  As a result, user to the contact's server (1)
       contact; (2) MUST send initiate a "roster push" to all of the contact's available
       resources associated with the contact that have requested the
       roster, containing an updated roster item for the user with the
       'subscription' attribute set to a value of "to"; (2) "both"; and (3) MUST
       route
       deliver the available presence stanza of type "unsubscribed" to the user,
       first stamping the 'from' address as the bare JID
       (<contact@otherdomain>) of the contact; and (3) SHOULD send
       unavailable presence from the contact to the user:




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   <iq type='set'>
     <query xmlns='jabber:iq:roster'>
       <item
           jid='user@somedomain'
           subscription='to'
           name='SomeUser'>
         <group>SomeGroup</group>
       </item>
     </query>
   </iq>

   <presence
       from='contact@otherdomain'
       to='user@somedomain'
       type='unsubscribed'/>

   <presence
       from='contact@otherdomain'
       to='user@somedomain'
       type='unavailable'/>

   3.  Upon receiving the presence stanza of type "unsubscribed"
       addressed to the user, the user's server (1) MUST initiate a
       "roster push" to all received from each of the
       user's available resources that have
       requested the roster, containing an updated roster item for the
       contact with the 'subscription' attribute set to a value each of
       "from" (if the user is offline, the user's server MUST modify the
       roster item and send that modified item the next time the user
       requests the roster); and (2) MUST deliver the "unsubscribed"
       state change notification to the user; and (3) MUST deliver the
       unavailable presence to the user: contact's available
       resources:

   <presence
       from='user@somedomain'
       to='contact@otherdomain'
       type='subscribed'/>

   <iq type='set'>
     <query xmlns='jabber:iq:roster'>
       <item
           jid='contact@otherdomain'
           subscription='from'
           name='MyContact'>
         <group>MyBuddies</group>
           jid='user@somedomain'
           subscription='both'
           name='SomeUser'>
         <group>SomeGroup</group>
       </item>
     </query>
   </iq>

   <presence
       from='contact@otherdomain'
       to='user@somedomain'
       type='unsubscribed'/>




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   <presence
       from='contact@otherdomain'
       to='user@somedomain'
       type='unavailable'/>

   4.
       from='user@somedomain/resource'
       to='contact@otherdomain/resource'/>

   6.  Upon receiving the presence stanza of type "unsubscribed", "subscribed", the
       user
       contact SHOULD acknowledge receipt of that subscription state
       notification through either "affirming" it by sending a presence
       stanza of type "unsubscribe" "subscribe" to the contact user or "denying" it by sending
       a presence stanza of type "subscribe" "unsubscribe" to the contact; user; this step
       does not necessarily affect the subscription state (see
       Section 8
       Subscription States (Section 9) for details), but instead lets
       the user's contact's server know that it must no longer send
       notification of the subscription state change to the user contact (see
       Section 8.6).

   Note: Obviously this does not result in removal of the roster item
   from the contact's roster, 9.6).

   The user and the contact still has now have a mutual subscription to each
   other's presence -- i.e., the user's presence. In order to both completely cancel a mutual subscription and fully remove the roster item from the contact's
   roster, the contact should update the roster item with
   subscription='remove' as defined in Section 7.6.

7.6 Removing a Roster Item and Cancelling All Subscriptions

   Because there may be many steps involved in completely removing a
   roster item and cancelling subscriptions in both directions, XMPP IM
   includes a "shortcut" method for doing so. is of type "both". The process may be
   initiated no matter what
   user's server MUST now send the user's current subscription state is by sending
   a roster set containing an item for the contact with the
   'subscription' attribute set presence information
   to a value of "remove":

   <iq type='set' id='remove1'>
     <query xmlns='jabber:iq:roster'>
       <item
           jid='contact@otherdomain'
           subscription='remove'/>
     </query>
   </iq>

   When the contact. (Note: If at this point the user removes sends a subscription
   request to the contact from his or her roster by setting the
   'subscription' attribute to contact sends a value of "remove", subscription request to
   the user, the sending user's server
   (1) MUST automatically cancel any existing presence silently ignore that request
   and not route it to the intended recipient.)

8.3.1 Alternate Flow: User Declines Subscription Request

   The above activity flow represents the "happy path" related to the
   contact's subscription
   between request to the user. The main alternate flow
   occurs if the user and refuses the contact (both 'to' and 'from' as
   appropriate); (2) MUST remove contact's subscription request.

   1.  If the roster item from user wants to refuse the user's roster
   and inform all of request, the user's available resources of the roster item
   removal; (3) client MUST inform the resource that initiated the removal of
   success; and (4) SHOULD
       send unavailable a presence stanza of type "unsubscribed" to the contact:




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   <presence
       from='user@somedomain'
       to='contact@otherdomain'
       type='unsubscribe'/>

   <presence
       from='user@somedomain'
       to='contact@otherdomain'
       type='unsubscribed'/>

   <iq type='set'>
     <query xmlns='jabber:iq:roster'>
       <item
           jid='contact@otherdomain'
           subscription='remove'/>
     </query>
   </iq>

   <iq type='result' id='remove1'/>

   <presence
       from='user@somedomain'
       to='contact@otherdomain'
       type='unavailable'/>

   Upon receiving contact
       (instead of the presence stanza of type "unsubscribe", "subscribed" sent in Step
       3 of Section 8.3):

   <presence to='contact@otherdomain' type='unsubscribed'/>

   2.  As a result, the
   contact's user's server (1) MUST initiate a "roster push" route the presence stanza of
       type "unsubscribed" to all available
   resources associated with the contact that have requested contact, first stamping the roster,
   containing an updated roster item for 'from'
       address as the user with bare JID (<user@somedomain>) of the
   'subscription' attribute set to a value user:

   <presence
       from='user@somedomain'
       to='contact@otherdomain'
       type='unsubscribed'/>

   3.  Upon receiving the presence stanza of "to" (if type "unsubscribed"
       addressed to the contact is
   offline, contact, the contact's server (1) MUST modify the roster item and send deliver
       that modified item the next time the contact requests presence stanza to the roster); contact; and (2) MUST also deliver the "unsubscribe" state change notification
   to the contact:

   <iq type='set'>
     <query xmlns='jabber:iq:roster'>
       <item
           jid='user@somedomain'
           subscription='to'
           name='SomeUser'>
         <group>SomeGroup</group>
       </item>
     </query>
   </iq>

   <presence
       from='user@somedomain' initiate a



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       to='contact@otherdomain'
       type='unsubscribe'/>

   Upon receiving the presence stanza of type "unsubscribed", the
   contact's server (1) MUST initiate a


       "roster push" to all available resources associated with the
       contact that have requested the roster, containing an updated
       roster item for the user with the 'subscription' attribute set to
       a value of "none" (if the contact is
   offline, the contact's server MUST modify the roster item and send
   that modified item the next time the contact requests the roster); "from" and (2) MUST also deliver the "unsubscribe" state change notification
   to the contact: with no 'ask' attribute:

   <presence
       from='user@somedomain'
       to='contact@otherdomain'
       type='unsubscribed'/>

   <iq type='set'>
     <query xmlns='jabber:iq:roster'>
       <item
           jid='user@somedomain'
           subscription='none'
           subscription='from'
           name='SomeUser'>
         <group>SomeGroup</group>
       </item>
     </query>
   </iq>

   <presence
       from='user@somedomain'
       to='contact@otherdomain'
       type='unsubscribed'/>

   4.  Upon receiving the presence stanza of type "unavailable" addressed to
   the contact, the contact's server MUST deliver "unsubscribed", the unavailable
   presence to the user:

   <presence
       from='user@somedomain'
       to='contact@otherdomain'
       type='unavailable'/>

   Note
       contact SHOULD acknowledge receipt of that when subscription state
       notification through either "affirming" it by sending a presence
       stanza of type "unsubscribe" to the user removes or "denying" it by
       sending a presence stanza of type "subscribe" to the contact from user; this
       step does not necessarily affect the user's roster, subscription state (see
       Subscription States (Section 9) for details), but instead lets
       the end contact's server know that it must no longer send
       notification of the subscription state change to the contact (see
       Section 9.6).

   As a result of this activity, there has been no change in the contact's roster
   subscription state; i.e., the contact is that in the user's roster with a
   subscription state of "to" and the user is still in the contact's roster
   with a subscription state of "none"; in order "from".

8.4 Unsubscribing

   At any time after subscribing to
   completely remove the roster item for a contact's presence, a user MAY
   unsubscribe. While the user, XML that the contact needs user sends to
   also send a roster removal request. make this happen is
   the same in all instances, the subsequent subscription state is
   different depending on the subscription state obtaining when the
   unsubscribe "command" was sent. Both possible scenarios are defined
   below.

8.4.1 Case #1: Unsubscribing When Subscription is Not Mutual




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8. Subscription States

   This section summarizes information about subscription states.

8.1 Defined States

   There are nine possible


   In the first case, the user has a subscription states:

   1.  "None" = you and I are not subscribed to each other, and neither
       of us has requested the contact but the
   contact does not have a subscription from to the user (i.e., the other

   2.  "None + Pending Out" = you and I are not subscribed to each
       other, and I've sent you a
   subscription request but you have is not
       responded yet

   3.  "None + Pending In" = you and I are not subscribed mutual).

   1.  If the user wants to each other,
       and you've sent me unsubscribe from the contact's presence, the
       user MUST send a subscription request but I have not
       responded yet

   4.  "None + Pending Out/In" = you and I are not subscribed presence stanza of type "unsubscribe" to each
       other, you've sent me a subscription request but I have not
       responded yet, and I've sent you the
       contact:

   <presence to='contact@otherdomain' type='unsubscribe'/>

   2.  As a subscription request but you
       have not responded yet

   5.  "To" = I'm subscribed to you (one-way)

   6.  "To + Pending In" = I'm subscribed to you, and you've result, the user's server (1) MUST send me a
       subscription request but I have not responded yet

   7.  "From" = you're subscribed to me (one-way)

   8.  "From + Pending Out" = you're subscribed "roster push" to me, and I've sent you
       a subscription request but you
       all of the user's available resources that have not responded yet

   9.  "Both" = we're subscribed requested the
       roster, containing an updated roster item for the contact with
       the 'subscription' attribute set to each other (two-way)


8.2 Server Handling of Outbound Presence, Categorized by Subscription
    State

   This section defines how a server value of "none"; and (2)
       MUST handle an outbound route the presence stanza of type "subscribe", "subscribed", "unsubscribe", and
   "unsubscribed" (i.e., route it "unsubscribe" to the intended recipient and/or make
   a change
       contact, first stamping the 'from' address as the bare JID
       (<user@somedomain>) of the user:

   <iq type='set'>
     <query xmlns='jabber:iq:roster'>
       <item
           jid='contact@otherdomain'
           subscription='none'
           name='MyContact'>
         <group>MyBuddies</group>
       </item>
     </query>
   </iq>

   <presence
       from='user@somedomain'
       to='contact@otherdomain'
       type='unsubscribe'/>

   3.  Upon receiving the presence stanza of type "unsubscribe"
       addressed to the subscription state), categorized by contact, the current
   subscription state. The general rule is contact's server (1) MUST initiate
       a "roster push" to all available resources associated with the
       contact that have requested the roster, containing an updated
       roster item for the user with the 'subscription' attribute set to
       a value of "none" (if the contact is offline, the contact's
       server MUST route modify the
   stanza to roster item and send that modified item
       the intended recipient if it would change next time the subscription
   state, contact requests the roster); and (2) MUST NOT route
       deliver the stanza if it would not "unsubscribe" state change notification to the
   subscription state. Detailed definitions are contained in the
       contact:

   <iq type='set'>
     <query xmlns='jabber:iq:roster'>
       <item



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   following sections. Naturally, if


           jid='user@somedomain'
           subscription='none'
           name='SomeUser'>
         <group>SomeGroup</group>
       </item>
     </query>
   </iq>

   <presence
       from='user@somedomain'
       to='contact@otherdomain'
       type='unsubscribe'/>

   4.  Upon receiving the presence stanza changes of type "unsubscribe", the
       contact SHOULD acknowledge receipt of that subscription
   state, state
       notification through either "affirming" it by sending a presence
       stanza of type "unsubscribed" to the server MUST also change user or "denying" it by
       sending a presence stanza of type "subscribed" to the user; this
       step does not necessarily affect the subscription state.

8.2.1 state (see
       Subscription State = None

   +-------------------------------------------------------+
   |  STANZA TYPE   |  ROUTE?  |  NEW STATE                |
   +-------------------------------------------------------+
   |  subscribe     |  yes     |  "None + Pending Out"     |
   |  subscribed    |  no      | States (Section 9) for details), but instead lets
       the contact's server know that it must no longer send
       notification of the subscription state change          |
   |  unsubscribe   |  no      |  no to the contact (see
       Section 9.6).

   5.  The contact's server then (1) MUST send a presence stanza of type
       "unsubscribed" to the user; and (2) SHOULD send unavailable
       presence from the contact to the user:

   <presence
       from='contact@otherdomain'
       to='user@somedomain'
       type='unsubscribed'/>

   <presence
       from='contact@otherdomain'
       to='user@somedomain'
       type='unavailable'/>

   6.  When the user's server receives a presence stanza of type
       "unsubscribed" and/or unavailable presence, it MUST deliver them
       to the user:

   <presence
       from='contact@otherdomain'
       to='user@somedomain'
       type='unsubscribed'/>

   <presence



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       from='contact@otherdomain'
       to='user@somedomain'
       type='unavailable'/>

   7.  Upon receiving the presence stanza of type "unsubscribed", the
       user SHOULD acknowledge receipt of that subscription state change          |
   |  unsubscribed  |  no      |  no
       notification through either "affirming" it by sending a presence
       stanza of type "unsubscribe" to the contact or "denying" it by
       sending a presence stanza of type "subscribe" to the contact;
       this step does not necessarily affect the subscription state change          |
   +-------------------------------------------------------+


8.2.2 (see
       Subscription State = None + Pending Out

   +-------------------------------------------------------+
   |  STANZA TYPE   |  ROUTE?  |  NEW STATE                |
   +-------------------------------------------------------+
   |  subscribe     |  no      |  no state change          |
   |  subscribed    |  no      |  no state change          |
   |  unsubscribe   |  yes     |  "None"                   |
   |  unsubscribed  |  no      | States (Section 9) for details), but instead lets
       the user's server know that it must no longer send notification
       of the subscription state change          |
   +-------------------------------------------------------+


8.2.3 Subscription State = None + Pending In

   +-------------------------------------------------------+
   |  STANZA TYPE   |  ROUTE?  |  NEW STATE                |
   +-------------------------------------------------------+
   |  subscribe     |  yes     |  "None + Pending Out/In"  |
   |  subscribed    |  yes     |  "From"                   |
   |  unsubscribe   |  no      |  no state change          |
   |  unsubscribed  |  yes     |  "None"                   |
   +-------------------------------------------------------+


8.2.4 to the user (see Section 9.6).


8.4.2 Case #2: Unsubscribing When Subscription State = None + Pending Out/In

   +-------------------------------------------------------+
   |  STANZA TYPE   |  ROUTE?  |  NEW STATE                |
   +-------------------------------------------------------+
   |  subscribe     |  no      |  no state change          |
   |  subscribed    |  yes     |  "From + Pending Out"     |
   | is Mutual

   In the second case, the user has a subscription to the contact and
   the contact also has a subscription to the user (i.e., the
   subscription is mutual).

   1.  If the user wants to unsubscribe   |  yes     |  "None + Pending In"      |
   |  unsubscribed  |  yes     |  "None + Pending Out"     | from the contact's presence, the
       user MUST send a presence stanza of type "unsubscribe" to the
       contact:

   <presence to='contact@otherdomain' type='unsubscribe'/>

   2.  As a result, the user's server (1) MUST send a "roster push" to
       all of the user's available resources that have requested the
       roster, containing an updated roster item for the contact with
       the 'subscription' attribute set to a value of "from"; and (2)
       MUST route the presence stanza of type "unsubscribe" to the
       contact, first stamping the 'from' address as the bare JID
       (<user@somedomain>) of the user:

   <iq type='set'>
     <query xmlns='jabber:iq:roster'>
       <item
           jid='contact@otherdomain'
           subscription='from'
           name='MyContact'>
         <group>MyBuddies</group>
       </item>
     </query>
   </iq>

   <presence
       from='user@somedomain'



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   +-------------------------------------------------------+


8.2.5 Subscription State = To

   +-------------------------------------------------------+
   |  STANZA TYPE   |  ROUTE?  |  NEW STATE                |
   +-------------------------------------------------------+
   |  subscribe     |  no      |  no


       to='contact@otherdomain'
       type='unsubscribe'/>

   3.  Upon receiving the presence stanza of type "unsubscribe"
       addressed to the contact, the contact's server (1) MUST initiate
       a "roster push" to all available resources associated with the
       contact that have requested the roster, containing an updated
       roster item for the user with the 'subscription' attribute set to
       a value of "to" (if the contact is offline, the contact's server
       MUST modify the roster item and send that modified item the next
       time the contact requests the roster); and (2) MUST deliver the
       "unsubscribe" state change          |
   |  subscribed    |  no      |  no notification to the contact:

   <iq type='set'>
     <query xmlns='jabber:iq:roster'>
       <item
           jid='user@somedomain'
           subscription='to'
           name='SomeUser'>
         <group>SomeGroup</group>
       </item>
     </query>
   </iq>

   <presence
       from='user@somedomain'
       to='contact@otherdomain'
       type='unsubscribe'/>

   4.  Upon receiving the presence stanza of type "unsubscribe", the
       contact SHOULD acknowledge receipt of that subscription state change          |
   |  unsubscribe   |  yes     |  "None"                   |
   |  unsubscribed  |  no      |  no
       notification through either "affirming" it by sending a presence
       stanza of type "unsubscribed" to the user or "denying" it by
       sending a presence stanza of type "subscribed" to the user; this
       step does not necessarily affect the subscription state change          |
   +-------------------------------------------------------+


8.2.6 (see
       Subscription State = To + Pending In

   +-------------------------------------------------------+
   |  STANZA TYPE   |  ROUTE?  |  NEW STATE                |
   +-------------------------------------------------------+
   |  subscribe     |  no      | States (Section 9) for details), but instead lets
       the contact's server know that it must no longer send
       notification of the subscription state change          |
   |  subscribed    |  yes     |  "Both"                   |
   |  unsubscribe   |  yes     |  "None + Pending In"      |
   |  unsubscribed  |  yes     |  "To"                     |
   +-------------------------------------------------------+


8.2.7 Subscription State = From

   +-------------------------------------------------------+
   |  STANZA TYPE   |  ROUTE?  |  NEW STATE                |
   +-------------------------------------------------------+
   |  subscribe     |  yes     |  "From + Pending Out"     |
   |  subscribed    |  no      |  no state change          |
   |  unsubscribe   |  no      |  no state change          |
   |  unsubscribed  |  yes     |  "None"                   |
   +-------------------------------------------------------+


8.2.8 Subscription State = From + Pending Out

   +-------------------------------------------------------+
   |  STANZA TYPE   |  ROUTE?  |  NEW STATE                |
   +-------------------------------------------------------+
   |  subscribe     |  no      |  no state change          |
   |  subscribed    |  no      |  no state change          |
   |  unsubscribe   |  yes     |  "From"                   |
   |  unsubscribed  |  yes     |  "None + Pending Out"     | to the contact (see
       Section 9.6).

   5.  The contact's server then (1) MUST send a presence stanza of type
       "unsubscribed" to the user; and (2) SHOULD send unavailable
       presence from the contact to the user:

   <presence
       from='contact@otherdomain'
       to='user@somedomain'
       type='unsubscribed'/>



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   +-------------------------------------------------------+


8.2.9 Subscription State = Both

   +-------------------------------------------------------+
   |  STANZA TYPE   |  ROUTE?  |  NEW STATE                |
   +-------------------------------------------------------+
   |  subscribe     |  no      |  no state change          |
   |  subscribed    |  no      |  no state change          |
   |  unsubscribe   |  yes     |  "From"                   |
   |  unsubscribed  |  yes     |  "To"                     |
   +-------------------------------------------------------+


8.3 Server Handling of Outbound Presence, Categorized by Presence Type

   This section defines how a


   <presence
       from='contact@otherdomain'
       to='user@somedomain'
       type='unavailable'/>

   6.  When the user's server MUST handle an outbound receives a presence stanza of type "subscribe", "subscribed", "unsubscribe", and
       "unsubscribed" (i.e., route and/or unavailable presence, it MUST deliver them
       to the intended recipient and/or make user:

   <presence
       from='contact@otherdomain'
       to='user@somedomain'
       type='unsubscribed'/>

   <presence
       from='contact@otherdomain'
       to='user@somedomain'
       type='unavailable'/>

   7.  Upon receiving the presence stanza of type "unsubscribed", the
       user SHOULD acknowledge receipt of that subscription state
       notification through either "affirming" it by sending a change presence
       stanza of type "unsubscribe" to the subscription state), categorized contact or "denying" it by
       sending a presence type.

8.3.1 Subscribe

   +----------------------------------------------------------------+
   |  EXISTING STATE          |  ROUTE?  |  NEW STATE               |
   +----------------------------------------------------------------+
   |  "None"                  |  yes     |  "None + Pending Out"    |
   |  "None + Pending Out"    |  no      |  no state change         |
   |  "None + Pending In"     |  yes     |  "None + Pending Out/In" |
   |  "None + Pending Out/In" |  no      |  no state change         |
   |  "To"                    |  no      |  no state change         |
   |  "To + Pending In"       |  no      |  no state change         |
   |  "From"                  |  yes     |  "From + Pending Out"    |
   |  "From + Pending Out"    |  no      |  no state change         |
   |  "Both"                  |  no      |  no state change         |
   +----------------------------------------------------------------+


8.3.2 Subscribed

   +----------------------------------------------------------------+
   |  EXISTING STATE          |  ROUTE?  |  NEW STATE               |
   +----------------------------------------------------------------+
   |  "None"                  |  no      |  no stanza of type "subscribe" to the contact;
       this step does not necessarily affect the subscription state change         |
   |  "None + Pending Out"    |  no      | (see
       Subscription States (Section 9) for details), but instead lets
       the user's server know that it must no longer send notification
       of the subscription state change         |
   |  "None + Pending In"     |  yes     |  "From"                  |
   |  "None + Pending Out/In" |  yes     |  "From + Pending Out"    | to the user (see Section 9.6).

   Note: Obviously this does not result in removal of the roster item
   from the user's roster, and the contact still has a subscription to
   the user's presence. In order to both completely cancel a mutual
   subscription and fully remove the roster item from the user's roster,
   the user should update the roster item with subscription='remove' as
   defined under Removing a Roster Item and Cancelling All Subscriptions
   (Section 8.6).

8.5 Cancelling a Subscription

   At any time after approving a subscription request from a user, a
   contact MAY cancel that subscription. While the XML that the contact
   sends to make this happen is the same in all instances, the
   subsequent subscription state is different depending on the
   subscription state obtaining when the cancellation was sent. Both
   possible scenarios are defined below.

8.5.1 Case #1: Cancelling When Subscription is Not Mutual




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   |  "To"                    |  no      |  no state change         |
   |  "To + Pending In"       |  yes     |  "Both"                  |
   |  "From"                  |  no      |  no state change         |
   |  "From + Pending Out"    |  no      |  no state change         |
   |  "Both"                  |  no      |  no state change         |
   +----------------------------------------------------------------+


8.3.3 Unsubscribe

   +----------------------------------------------------------------+
   |  EXISTING STATE          |  ROUTE?  |  NEW STATE               |
   +----------------------------------------------------------------+
   |  "None"                  |  no      |  no state change         |
   |  "None + Pending Out"    |  no      |  no state change         |
   |  "None + Pending In"     |  no      |  no state change         |
   |  "None + Pending Out/In" |  yes     |  "None + Pending In"     |
   |  "To"                    |  yes     |  "None"                  |
   |  "To + Pending In"       |  yes     |  "None + Pending In"     |
   |  "From"                  |  no      |  no state change         |
   |  "From + Pending Out"    |  yes     |  "From"                  |
   |  "Both"                  |  yes     |  "From"                  |
   +----------------------------------------------------------------+

   Note: When


   In the first case, the user has a subscription to the contact but the
   contact does not have a subscription to the user sends an outbound (i.e., the
   subscription is not yet mutual).

   1.  If the contact wants to cancel the user's subscription, the
       contact MUST send a presence stanza of type
   "unsubscribe" that results in "unsubscribed" to the
       user:

   <presence to='user@somedomain' type='unsubscribed'/>

   2.  As a subscription state change, result, the contact's server SHOULD auto-reply by sending (1) MUST send a "roster push"
       to all of the contact's available resources that have requested
       the roster, containing an updated roster item for the user with
       the 'subscription' attribute set to a value of "none"; (2) MUST
       route the presence stanza of type "unsubscribed" to the user on behalf user,
       first stamping the 'from' address as the bare JID
       (<contact@otherdomain>) of the contact contact; and MUST
   deliver that (3) SHOULD send
       unavailable presence from the contact to the user:

   <iq type='set'>
     <query xmlns='jabber:iq:roster'>
       <item
           jid='user@somedomain'
           subscription='none'
           name='SomeUser'>
         <group>SomeGroup</group>
       </item>
     </query>
   </iq>

   <presence
       from='contact@otherdomain'
       to='user@somedomain'
       type='unsubscribed'/>

   <presence
       from='contact@otherdomain'
       to='user@somedomain'
       type='unavailable'/>

   3.  Upon receiving the presence stanza of type "unsubscribed"
       addressed to the contact.

8.3.4 Unsubscribed

   +----------------------------------------------------------------+
   |  EXISTING STATE          |  ROUTE?  |  NEW STATE               |
   +----------------------------------------------------------------+
   |  "None"                  |  no      |  no state change         |
   |  "None + Pending Out"    |  no      |  no state change         |
   |  "None + Pending In"     |  yes     |  "None"                  |
   |  "None + Pending Out/In" |  yes     |  "None + Pending Out"    |
   |  "To"                    |  no      |  no user, the user's server (1) MUST initiate a
       "roster push" to all of the user's available resources that have
       requested the roster, containing an updated roster item for the
       contact with the 'subscription' attribute set to a value of
       "none" (if the user is offline, the user's server MUST modify the
       roster item and send that modified item the next time the user
       requests the roster); (2) MUST deliver the "unsubscribed" state change         |
   |  "To + Pending In"       |  yes     |  "To"                    |
   |  "From"                  |  yes     |  "None"                  |
   |  "From + Pending Out"    |  yes     |  "None + Pending Out"    |
   |  "Both"                  |  yes     |  "To"                    |
   +----------------------------------------------------------------+



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8.4 Server Handling of Inbound Presence, Categorized by Subscription
    State

   This section defines how a server


       change notification to the user; and (3) MUST handle an inbound deliver the
       unavailable presence to the user:

   <iq type='set'>
     <query xmlns='jabber:iq:roster'>
       <item
           jid='contact@otherdomain'
           subscription='none'
           name='MyContact'>
         <group>MyBuddies</group>
       </item>
     </query>
   </iq>

   <presence
       from='contact@otherdomain'
       to='user@somedomain'
       type='unsubscribed'/>

   <presence
       from='contact@otherdomain'
       to='user@somedomain'
       type='unavailable'/>

   4.  Upon receiving the presence stanza of type "subscribe", "subscribed", "unsubscribe", and
   "unsubscribed" (i.e., deliver it to the intended recipient and/or
   make a change to "unsubscribed", the
       user SHOULD acknowledge receipt of that subscription state), categorized state
       notification through either "affirming" it by subscription
   state. (Note: some sending a presence
       stanza of type "unsubscribe" to the contact or "denying" it by
       sending a presence stanza of type should never be
   received as inbound stanzas, since the sender's server MUST NOT route
   them "subscribe" to the intended recipient; however, these stanza types are
   included for contact;
       this step does not necessarily affect the sake of completeness.)

8.4.1 Subscription State = None

   +--------------------------------------------------------+
   |  STANZA TYPE   |  DELIVER?  |  NEW STATE               |
   +--------------------------------------------------------+
   |  subscribe     |  yes       |  "None + Pending In"     |
   |  subscribed    |  no        |  no state change         |
   |  unsubscribe   |  no        |  no state change         |
   |  unsubscribed  |  no        |  no subscription state change         |
   +--------------------------------------------------------+


8.4.2 (see
       Subscription State = None + Pending Out

   +--------------------------------------------------------+
   |  STANZA TYPE   |  DELIVER?  |  NEW STATE               |
   +--------------------------------------------------------+
   |  subscribe     |  yes       |  "None + Pending Out/In" |
   |  subscribed    |  yes       |  "To"                    |
   |  unsubscribe   |  no        | States (Section 9) for details), but instead lets
       the user's server know that it must no longer send notification
       of the subscription state change         |
   |  unsubscribed  |  yes       |  "None"                  |
   +--------------------------------------------------------+


8.4.3 to the user (see Section 9.6).


8.5.2 Case #2: Cancelling When Subscription State = None + Pending is Mutual

   In

   +--------------------------------------------------------+
   |  STANZA TYPE   |  DELIVER?  |  NEW STATE               |
   +--------------------------------------------------------+
   |  subscribe     |  no        |  no state change         |
   |  subscribed    |  no        |  no state change         |
   |  unsubscribe   |  yes       |  "None"                  |
   |  unsubscribed  |  no        |  no state change         |
   +--------------------------------------------------------+





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8.4.4 Subscription State = None + Pending Out/In

   +--------------------------------------------------------+
   |  STANZA TYPE   |  DELIVER?  |  NEW STATE               |
   +--------------------------------------------------------+
   |  subscribe     |  no        |  no state change         |
   |  subscribed    |  yes       |  "To + Pending In"       |
   |  unsubscribe   |  yes       |  "None + Pending Out"    |
   |  unsubscribed  |  yes       |  "None + Pending In"     |
   +--------------------------------------------------------+


8.4.5 Subscription State = To

   +--------------------------------------------------------+
   |  STANZA TYPE   |  DELIVER?  |  NEW STATE               |
   +--------------------------------------------------------+
   |  subscribe     |  yes       |  "To + Pending In"       |
   |  subscribed    |  no        |  no state change         |
   |  unsubscribe   |  no        |  no state change         |
   |  unsubscribed  |  yes       |  "None"                  |
   +--------------------------------------------------------+


8.4.6 Subscription State = To + Pending In

   +--------------------------------------------------------+
   |  STANZA TYPE   |  DELIVER?  |  NEW STATE               |
   +--------------------------------------------------------+
   |  subscribe     |  no        |  no state change         |
   |  subscribed    |  no        |  no state change         |
   |  unsubscribe   |  yes       |  "To"                    |
   |  unsubscribed  |  yes       |  "None + Pending In"     |
   +--------------------------------------------------------+


8.4.7 Subscription State = From

   +--------------------------------------------------------+
   |  STANZA TYPE   |  DELIVER?  |  NEW STATE               |
   +--------------------------------------------------------+
   |  subscribe     |  no        |  no state change         |
   |  subscribed    |  no        |  no state change         |
   |  unsubscribe   |  yes       |  "None"                  |
   |  unsubscribed  |  no        |  no state change         |
   +--------------------------------------------------------+ the second case, the user has a subscription to the contact and
   the contact also has a subscription to the user (i.e., the
   subscription is mutual).

   1.  If the contact wants to cancel the user's subscription, the
       contact MUST send a presence stanza of type "unsubscribed" to the
       user:

   <presence to='user@somedomain' type='unsubscribed'/>





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8.4.8 Subscription State = From + Pending Out

   +--------------------------------------------------------+
   |  STANZA TYPE   |  DELIVER?  |  NEW STATE               |
   +--------------------------------------------------------+
   |  subscribe     |  no        |  no state change         |
   |  subscribed    |  yes       |  "Both"                  |
   |  unsubscribe   |  yes       |  "None + Pending Out"    |
   |  unsubscribed  |  yes       |  "From"                  |
   +--------------------------------------------------------+


8.4.9 Subscription State = Both

   +--------------------------------------------------------+
   |  STANZA TYPE   |  DELIVER?  |  NEW STATE               |
   +--------------------------------------------------------+
   |  subscribe     |  no        |  no state change         |
   |  subscribed    |  no        |  no state change         |
   |  unsubscribe   |  yes       |  "To"                    |
   |  unsubscribed  |  yes       |  "From"                  |
   +--------------------------------------------------------+


8.5 Server Handling of Inbound Presence, Categorized by Presence Type

   This section defines how


   2.  As a result, the contact's server (1) MUST handle send a "roster push"
       to all of the contact's available resources that have requested
       the roster, containing an inbound updated roster item for the user with
       the 'subscription' attribute set to a value of "to"; (2) MUST
       route the presence stanza of type "subscribe", "subscribed", "unsubscribe", "unsubscribed" to the user,
       first stamping the 'from' address as the bare JID
       (<contact@otherdomain>) of the contact; and (3) SHOULD send
       unavailable presence from the contact to the user:

   <iq type='set'>
     <query xmlns='jabber:iq:roster'>
       <item
           jid='user@somedomain'
           subscription='to'
           name='SomeUser'>
         <group>SomeGroup</group>
       </item>
     </query>
   </iq>

   <presence
       from='contact@otherdomain'
       to='user@somedomain'
       type='unsubscribed'/>

   <presence
       from='contact@otherdomain'
       to='user@somedomain'
       type='unavailable'/>

   3.  Upon receiving the presence stanza of type "unsubscribed" (i.e., deliver it
       addressed to the intended recipient and/or
   make user, the user's server (1) MUST initiate a change
       "roster push" to all of the subscription state), categorized by presence
   type.

8.5.1 Subscribe

   +------------------------------------------------------------------+
   |  EXISTING STATE          |  DELIVER?  |  NEW STATE               |
   +------------------------------------------------------------------+
   |  "None"                  |  yes       |  "None + Pending In"     |
   |  "None + Pending Out"    |  yes       |  "None + Pending Out/In" |
   |  "None + Pending In"     |  no        |  no state change         |
   |  "None + Pending Out/In" |  no        |  no state change         |
   |  "To"                    |  yes       |  "To + Pending In"       |
   |  "To + Pending In"       |  no        |  no state change         |
   |  "From"                  |  no        |  no state change         |
   |  "From + Pending Out"    |  no        |  no state change         |
   |  "Both"                  |  no        |  no user's available resources that have
       requested the roster, containing an updated roster item for the
       contact with the 'subscription' attribute set to a value of
       "from" (if the user is offline, the user's server MUST modify the
       roster item and send that modified item the next time the user
       requests the roster); and (2) MUST deliver the "unsubscribed"
       state change         |
   +------------------------------------------------------------------+ notification to the user; and (3) MUST deliver the
       unavailable presence to the user:

   <iq type='set'>
     <query xmlns='jabber:iq:roster'>
       <item
           jid='contact@otherdomain'
           subscription='from'
           name='MyContact'>
         <group>MyBuddies</group>



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8.5.2 Subscribed

   +------------------------------------------------------------------+
   |  EXISTING STATE          |  DELIVER?  |  NEW STATE               |
   +------------------------------------------------------------------+
   |  "None"                  |  no        |  no state change         |
   |  "None + Pending Out"    |  yes       |  "To"                    |
   |  "None + Pending In"     |  no        |  no


       </item>
     </query>
   </iq>

   <presence
       from='contact@otherdomain'
       to='user@somedomain'
       type='unsubscribed'/>

   <presence
       from='contact@otherdomain'
       to='user@somedomain'
       type='unavailable'/>

   4.  Upon receiving the presence stanza of type "unsubscribed", the
       user SHOULD acknowledge receipt of that subscription state change         |
   |  "None + Pending Out/In" |  yes       |  "To + Pending In"       |
   |  "To"                    |  no        |  no state change         |
   |  "To + Pending In"       |  no        |  no state change         |
   |  "From"                  |  no        |  no
       notification through either "affirming" it by sending a presence
       stanza of type "unsubscribe" to the contact or "denying" it by
       sending a presence stanza of type "subscribe" to the contact;
       this step does not necessarily affect the subscription state change         |
   |  "From + Pending Out"    |  yes       |  "Both"                  |
   |  "Both"                  |  no        | (see
       Subscription States (Section 9) for details), but instead lets
       the user's server know that it must no longer send notification
       of the subscription state change         |
   +------------------------------------------------------------------+


8.5.3 Unsubscribe

   +------------------------------------------------------------------+
   |  EXISTING STATE          |  DELIVER?  |  NEW STATE               |
   +------------------------------------------------------------------+
   |  "None"                  |  no        | to the user (see Section 9.6).

   Note: Obviously this does not result in removal of the roster item
   from the contact's roster, and the contact still has a subscription
   to the user's presence. In order to both completely cancel a mutual
   subscription and fully remove the roster item from the contact's
   roster, the contact should update the roster item with
   subscription='remove' as defined under Removing a Roster Item and
   Cancelling All Subscriptions (Section 8.6).

8.6 Removing a Roster Item and Cancelling All Subscriptions

   Because there may be many steps involved in completely removing a
   roster item and cancelling subscriptions in both directions, XMPP IM
   includes a "shortcut" method for doing so. The process may be
   initiated no matter what the current subscription state change         |
   |  "None + Pending Out"    |  no        |  no state change         |
   |  "None + Pending In"     |  yes       |  "None"                  |
   |  "None + Pending Out/In" |  yes       |  "None + Pending Out"    |
   |  "To"                    |  no        |  no state change         |
   |  "To + Pending In"       |  yes       |  "To"                    |
   |  "From"                  |  yes       |  "None"                  |
   |  "From + Pending Out"    |  yes       |  "None + Pending Out     |
   |  "Both"                  |  yes       |  "To"                    |
   +------------------------------------------------------------------+


8.5.4 Unsubscribed

   +------------------------------------------------------------------+
   |  EXISTING STATE          |  DELIVER?  |  NEW STATE               |
   +------------------------------------------------------------------+
   |  "None"                  |  no        |  no state change         |
   |  "None + Pending Out"    |  yes       |  "None"                  |
   |  "None + Pending In"     |  no        |  no state change         |
   |  "None + Pending Out/In" |  yes       |  "None + Pending In"     |
   |  "To"                    |  yes       |  "None"                  |
   |  "To + Pending In"       |  yes       |  "None + Pending In"     |
   |  "From"                  |  no        |  no state change         |
   |  "From + Pending Out"    |  yes       |  "From"                  |
   |  "Both"                  |  yes       |  "From"                  | is by sending
   a roster set containing an item for the contact with the
   'subscription' attribute set to a value of "remove":

   <iq type='set' id='remove1'>
     <query xmlns='jabber:iq:roster'>
       <item
           jid='contact@otherdomain'
           subscription='remove'/>
     </query>
   </iq>



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   +------------------------------------------------------------------+


8.6 Server Delivery and Client Acknowledgement of Subscription State
    Change Notifications


   When the user removes a server receives an inbound presence contact from his or her roster by setting the
   'subscription' attribute to a value of type "subscribe",
   "subscribed", "unsubscribe", and "unsubscribed" that consists of a "remove", the user's server
   (1) MUST automatically cancel any existing presence subscription state change notification, in addition to sending
   between the user and the contact (both 'to' and 'from' as
   appropriate); (2) MUST remove the
   appropriate "roster push" (or updated roster when item from the user's roster is next
   requested), it MUST deliver
   and inform all of the notification to user's available resources of the intended
   recipient at least once.

   A server roster item
   removal; (3) MUST require inform the recipient resource that initiated the removal of
   success; and (4) SHOULD send unavailable presence to approve or refuse a
   subscription request (i.e., an inbound the contact:

   <presence
       from='user@somedomain'
       to='contact@otherdomain'
       type='unsubscribe'/>

   <presence
       from='user@somedomain'
       to='contact@otherdomain'
       type='unsubscribed'/>

   <iq type='set'>
     <query xmlns='jabber:iq:roster'>
       <item
           jid='contact@otherdomain'
           subscription='remove'/>
     </query>
   </iq>

   <iq type='result' id='remove1'/>

   <presence
       from='user@somedomain'
       to='contact@otherdomain'
       type='unavailable'/>

   Upon receiving the presence stanza of type
   "subscribe") and MAY require "unsubscribe", the recipient
   contact's server (1) MUST initiate a "roster push" to acknowledge receipt of all available
   resources associated with the state change notification. In order contact that have requested the roster,
   containing an updated roster item for the user with the
   'subscription' attribute set to require acknowledgement, a value of "to" (if the contact is
   offline, the contact's server SHOULD send MUST modify the notification to roster item and send
   that modified item the recipient each next time the
   recipient logs in, until contact requests the recipient acknowledges receipt of roster);
   and (2) MUST also deliver the "unsubscribe" state change notification by "affirming" or "denying" the notification, as shown
   in
   to the following table:

   +--------------------------------------------------+
   |  NOTIFICATION  |  ACCEPT        |  DENY          |
   +--------------------------------------------------+
   |  subscribe     |  subscribed    |  unsubscribed  |
   |  subscribed    |  subscribe     |  unsubscribe   |
   |  unsubscribe   |  unsubscribed  |  subscribed    |
   |  unsubscribed  |  unsubscribe   |  subscribe     |
   +--------------------------------------------------+

   Obviously, given the foregoing subscription state charts, some contact:

   <iq type='set'>
     <query xmlns='jabber:iq:roster'>
       <item
           jid='user@somedomain'



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           subscription='to'
           name='SomeUser'>
         <group>SomeGroup</group>
       </item>
     </query>
   </iq>

   <presence
       from='user@somedomain'
       to='contact@otherdomain'
       type='unsubscribe'/>

   Upon receiving the
   acknowledgement and denial stanzas will be routed to presence stanza of type "unsubscribed", the contact and
   result in subscription state changes, while others will not. However,
   any such stanzas
   contact's server (1) MUST result in the server's no longer sending the
   subscription state notification initiate a "roster push" to all available
   resources associated with the user.

   Because contact that have requested the sender's server MUST automatically generate outbound
   presence stanzas of type "unsubscribe" and "unsubscribed" upon
   receiving a roster,
   containing an updated roster set item for the user with the
   'subscription' attribute set to a value of "remove" (see Section 7.6), "none" (if the contact is
   offline, the contact's server MUST treat a modify the roster
   remove request as equivalent to sending those presence stanzas for
   purposes of determining whether to continue sending subscription item and send
   that modified item the next time the contact requests the roster);
   and (2) MUST also deliver the "unsubscribe" state change notifications notification
   to the contact:

   <iq type='set'>
     <query xmlns='jabber:iq:roster'>
       <item
           jid='user@somedomain'
           subscription='none'
           name='SomeUser'>
         <group>SomeGroup</group>
       </item>
     </query>
   </iq>

   <presence
       from='user@somedomain'
       to='contact@otherdomain'
       type='unsubscribed'/>

   Upon receiving the presence stanza of type "subscribe" or "subscribed" "unavailable" addressed to
   the
   user. contact, the contact's server MUST deliver the unavailable
   presence to the user:

   <presence
       from='user@somedomain'
       to='contact@otherdomain'
       type='unavailable'/>

   Note that when the user removes the contact from the user's roster,



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9. Blocking Communication

   Most instant messaging systems have found it necessary to implement
   some method for users to block communications from particular other
   users (this is also required by sections 5.1.5, 5.1.15, 5.3.2, and
   5.4.10 of RFC 2779 [2]). In XMPP this is done using


   the
   'jabber:iq:privacy' namespace by managing one's privacy lists.

   Server-side privacy lists enable successful completion end state of the
   following use cases:

   o  Retrieving one's privacy lists.

   o  Adding, removing, and editing one's privacy lists.

   o  Setting, changing, or declining active lists.

   o  Setting, changing, or declining the default list (i.e., the list
      that contact's roster is active by default).

   o  Allowing or blocking messages based on JID, group, or subscription
      type (or globally).

   o  Allowing or blocking inbound presence notifications based on JID,
      group, or subscription type (or globally).

   o  Allowing or blocking outbound presence notifications based on JID,
      group, or subscription type (or globally).

   o  Allowing or blocking IQs based on JID, group, or subscription type
      (or globally).

   o  Allowing or blocking all communications based on JID, group, or
      subscription type (or globally).

   Note: presence notifications do not include presence subscriptions,
   only presence information that the user is broadcasted to entities that are
   subscribed to a user's presence information. Thus this includes
   presence stanzas still in
   the contact's roster with no 'type' attribute or a subscription state of type='unavailable'
   only.

9.1 Syntax

   A user MAY define one or more privacy lists, which are stored by the
   user's server. Each <list/> element contains one or more rules "none"; in order to
   completely remove the
   form of <item/> elements, and each <item/> element uses attributes to
   define a privacy rule type, a specific value to which the rules
   applies, the relevant action, and the place of the roster item in for the user, the contact needs to
   also send a roster removal request.















































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   processing order.

   The syntax is as follows:

   <iq>
     <query xmlns='jabber:iq:privacy'>
       <list name='foo'>
         <item
             type='[jid|group|subscription]'
             value='bar'
             action='[accept|deny]'
             order='unsignedInt'/>
       </list>
     </query>
   </iq>

   If the type is "jid", then the 'value' attribute MUST contain a valid
   Jabber ID. JIDs


9. Subscription States

   This section summarizes information about subscription states.

9.1 Defined States

   There are matched in the following order: <user@somedomain/
   resource>, then <user@somedomain>, then <somedomain/resource>, then
   <somedomain>. If the value is <user@somedomain>, then any connected
   resource for that user@somedomain matches. If the value is
   <somedomain/resource>, then only that resource matches. If the value
   is <somedomain>, then any user@somedomain (or subdomain) matches.

   If the type is "group", then the 'value' attribute SHOULD contain the
   name nine possible subscription states:

   1.  "None" = you and I are not subscribed to each other, and neither
       of us has requested a group in subscription from the user's roster. (If a client attempts other

   2.  "None + Pending Out" = you and I are not subscribed to
   update, create, or delete a list item with each
       other, and I've sent you a group that is subscription request but you have not in the
   user's roster, the server SHOULD return
       responded yet

   3.  "None + Pending In" = you and I are not subscribed to the client an
   <item-not-found/> stanza error.)

   If the type is "subscription", then the 'value' attribute MUST be one
   of "both", "to", "from", or "none" as defined in XMPP Core [1].

   If no 'type' attribute is included, the rule provides the
   "fall-through" case.

   The 'action' attribute MUST be included each other,
       and its value MUST be either
   "accept" or "deny".

   The 'order' attribute MUST be included you've sent me a subscription request but I have not
       responded yet

   4.  "None + Pending Out/In" = you and its value MUST be I are not subscribed to each
       other, you've sent me a
   non-negative integer that is unique among all items in the list. (If subscription request but I have not
       responded yet, and I've sent you a client attempts subscription request but you
       have not responded yet

   5.  "To" = I'm subscribed to create or update you (one-way)

   6.  "To + Pending In" = I'm subscribed to you, and you've send me a list with non-unique order
   values, the server MUST return
       subscription request but I have not responded yet

   7.  "From" = you're subscribed to the client me (one-way)

   8.  "From + Pending Out" = you're subscribed to me, and I've sent you
       a <bad-request/> stanza
   error.

   Within the 'jabber:iq:privacy' namespace, the <query/> child subscription request but you have not responded yet

   9.  "Both" = we're subscribed to each other (two-way)


9.2 Server Handling of Outbound Presence, Categorized by Subscription
    State

   This section defines how a
   client-generated IQ server MUST handle an outbound presence
   stanza of type "set" MUST NOT include more than
   one child element "subscribe", "subscribed", "unsubscribe", and
   "unsubscribed" (i.e., route it to the stanza must contain only one <active/>



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   element, one <default/> element, or one <list/> element); if intended recipient and/or make
   a client
   violates this rule, the server MUST return change to the client a
   <bad-request/> stanza error.)

   When a client adds or updates a privacy list, subscription state), categorized by the <list/> element
   SHOULD contain at least one <item/> child element; when a client
   removes current
   subscription state. The general rule is that a privacy list, server MUST route the <list/> element SHOULD contain no <item/>
   child element.

   When a client updates a privacy list, it must include all of
   stanza to the
   desired items (i.e., not a "delta").

9.2 Business Rules

   1.  If there is an active list set for a session, intended recipient if it affects only would change the
       session for which it is activated, subscription
   state, and only for the duration of
       the session. Only MUST NOT route the active list for that session is processed
       (i.e., stanza if it would not change the default list is ignored).

   2.  The default list applies to
   subscription state. Detailed definitions are contained in the user as a whole, and is processed



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   following sections. Naturally, if there is no active list set for the target session/resource to
       which a stanza is addressed, or if there are no current sessions
       for changes the user.

   3.  If there is no active list set for a session (or there are no
       current sessions for the user), and there is no default list,
       then all stanzas SHOULD BE accepted or appropriately processed by
       the server on behalf of the user.

   4.  Privacy lists SHOULD be the first routing and delivery rule
       applied by a server, trumping the other rules specified in
       Section 10.

   5.  The order in which privacy list items are processed by the server
       is important. List items MUST be processed in ascending order
       determined by the values of the 'order' attribute for each <item/
       >.

   6.  As soon as a stanza is matched against a privacy list, subscription
   state, the server
       SHOULD appropriately handle the stanza and cease processing.

   7.  If no fall-through item is provided in a list, the fall-through
       action is assumed to be "accept".

   8.  If a user updates the definition for an active list, subsequent
       processing based on that active list MUST use the updated
       definition (for all resources to which that active list currently
       applies).



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   9.  If a also change to the subscription state.

9.2.1 Subscription State = None

   +-------------------------------------------------------+
   |  STANZA TYPE   |  ROUTE?  |  NEW STATE                |
   +-------------------------------------------------------+
   |  subscribe     |  yes     |  "None + Pending Out"     |
   |  subscribed    |  no      |  no state or roster group of a roster
       item defined in an active list occurs during a user's session,
       subsequent processing based on that active list MUST take into
       account the changed change          |
   |  unsubscribe   |  no      |  no state or group (for all resources to which
       that active list currently applies).


9.3 Retrieving One's Privacy Lists

   Example: Client requests names of change          |
   |  unsubscribed  |  no      |  no state change          |
   +-------------------------------------------------------+


9.2.2 Subscription State = None + Pending Out

   +-------------------------------------------------------+
   |  STANZA TYPE   |  ROUTE?  |  NEW STATE                |
   +-------------------------------------------------------+
   |  subscribe     |  no      |  no state change          |
   |  subscribed    |  no      |  no state change          |
   |  unsubscribe   |  yes     |  "None"                   |
   |  unsubscribed  |  no      |  no state change          |
   +-------------------------------------------------------+


9.2.3 Subscription State = None + Pending In

   +-------------------------------------------------------+
   |  STANZA TYPE   |  ROUTE?  |  NEW STATE                |
   +-------------------------------------------------------+
   |  subscribe     |  yes     |  "None + Pending Out/In"  |
   |  subscribed    |  yes     |  "From"                   |
   |  unsubscribe   |  no      |  no state change          |
   |  unsubscribed  |  yes     |  "None"                   |
   +-------------------------------------------------------+


9.2.4 Subscription State = None + Pending Out/In

   +-------------------------------------------------------+
   |  STANZA TYPE   |  ROUTE?  |  NEW STATE                |
   +-------------------------------------------------------+
   |  subscribe     |  no      |  no state change          |
   |  subscribed    |  yes     |  "From + Pending Out"     |
   |  unsubscribe   |  yes     |  "None + Pending In"      |
   |  unsubscribed  |  yes     |  "None + Pending Out"     |



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   +-------------------------------------------------------+


9.2.5 Subscription State = To

   +-------------------------------------------------------+
   |  STANZA TYPE   |  ROUTE?  |  NEW STATE                |
   +-------------------------------------------------------+
   |  subscribe     |  no      |  no state change          |
   |  subscribed    |  no      |  no state change          |
   |  unsubscribe   |  yes     |  "None"                   |
   |  unsubscribed  |  no      |  no state change          |
   +-------------------------------------------------------+


9.2.6 Subscription State = To + Pending In

   +-------------------------------------------------------+
   |  STANZA TYPE   |  ROUTE?  |  NEW STATE                |
   +-------------------------------------------------------+
   |  subscribe     |  no      |  no state change          |
   |  subscribed    |  yes     |  "Both"                   |
   |  unsubscribe   |  yes     |  "None + Pending In"      |
   |  unsubscribed  |  yes     |  "To"                     |
   +-------------------------------------------------------+


9.2.7 Subscription State = From

   +-------------------------------------------------------+
   |  STANZA TYPE   |  ROUTE?  |  NEW STATE                |
   +-------------------------------------------------------+
   |  subscribe     |  yes     |  "From + Pending Out"     |
   |  subscribed    |  no      |  no state change          |
   |  unsubscribe   |  no      |  no state change          |
   |  unsubscribed  |  yes     |  "None"                   |
   +-------------------------------------------------------+


9.2.8 Subscription State = From + Pending Out

   +-------------------------------------------------------+
   |  STANZA TYPE   |  ROUTE?  |  NEW STATE                |
   +-------------------------------------------------------+
   |  subscribe     |  no      |  no state change          |
   |  subscribed    |  no      |  no state change          |
   |  unsubscribe   |  yes     |  "From"                   |
   |  unsubscribed  |  yes     |  "None + Pending Out"     |



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   +-------------------------------------------------------+


9.2.9 Subscription State = Both

   +-------------------------------------------------------+
   |  STANZA TYPE   |  ROUTE?  |  NEW STATE                |
   +-------------------------------------------------------+
   |  subscribe     |  no      |  no state change          |
   |  subscribed    |  no      |  no state change          |
   |  unsubscribe   |  yes     |  "From"                   |
   |  unsubscribed  |  yes     |  "To"                     |
   +-------------------------------------------------------+


9.3 Server Handling of Outbound Presence, Categorized by Presence Type

   This section defines how a server MUST handle an outbound presence
   stanza of type "subscribe", "subscribed", "unsubscribe", and
   "unsubscribed" (i.e., route it to the intended recipient and/or make
   a change to the subscription state), categorized by presence type.

9.3.1 Subscribe

   +----------------------------------------------------------------+
   |  EXISTING STATE          |  ROUTE?  |  NEW STATE               |
   +----------------------------------------------------------------+
   |  "None"                  |  yes     |  "None + Pending Out"    |
   |  "None + Pending Out"    |  no      |  no state change         |
   |  "None + Pending In"     |  yes     |  "None + Pending Out/In" |
   |  "None + Pending Out/In" |  no      |  no state change         |
   |  "To"                    |  no      |  no state change         |
   |  "To + Pending In"       |  no      |  no state change         |
   |  "From"                  |  yes     |  "From + Pending Out"    |
   |  "From + Pending Out"    |  no      |  no state change         |
   |  "Both"                  |  no      |  no state change         |
   +----------------------------------------------------------------+


9.3.2 Subscribed

   +----------------------------------------------------------------+
   |  EXISTING STATE          |  ROUTE?  |  NEW STATE               |
   +----------------------------------------------------------------+
   |  "None"                  |  no      |  no state change         |
   |  "None + Pending Out"    |  no      |  no state change         |
   |  "None + Pending In"     |  yes     |  "From"                  |
   |  "None + Pending Out/In" |  yes     |  "From + Pending Out"    |



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   |  "To"                    |  no      |  no state change         |
   |  "To + Pending In"       |  yes     |  "Both"                  |
   |  "From"                  |  no      |  no state change         |
   |  "From + Pending Out"    |  no      |  no state change         |
   |  "Both"                  |  no      |  no state change         |
   +----------------------------------------------------------------+


9.3.3 Unsubscribe

   +----------------------------------------------------------------+
   |  EXISTING STATE          |  ROUTE?  |  NEW STATE               |
   +----------------------------------------------------------------+
   |  "None"                  |  no      |  no state change         |
   |  "None + Pending Out"    |  no      |  no state change         |
   |  "None + Pending In"     |  no      |  no state change         |
   |  "None + Pending Out/In" |  yes     |  "None + Pending In"     |
   |  "To"                    |  yes     |  "None"                  |
   |  "To + Pending In"       |  yes     |  "None + Pending In"     |
   |  "From"                  |  no      |  no state change         |
   |  "From + Pending Out"    |  yes     |  "From"                  |
   |  "Both"                  |  yes     |  "From"                  |
   +----------------------------------------------------------------+

   Note: When a user sends an outbound presence stanza of type
   "unsubscribe" that results in a subscription state change, the
   contact's server SHOULD auto-reply by sending a presence stanza of
   type "unsubscribed" to the user on behalf of the contact and MUST
   deliver that presence stanza to the contact.

9.3.4 Unsubscribed

   +----------------------------------------------------------------+
   |  EXISTING STATE          |  ROUTE?  |  NEW STATE               |
   +----------------------------------------------------------------+
   |  "None"                  |  no      |  no state change         |
   |  "None + Pending Out"    |  no      |  no state change         |
   |  "None + Pending In"     |  yes     |  "None"                  |
   |  "None + Pending Out/In" |  yes     |  "None + Pending Out"    |
   |  "To"                    |  no      |  no state change         |
   |  "To + Pending In"       |  yes     |  "To"                    |
   |  "From"                  |  yes     |  "None"                  |
   |  "From + Pending Out"    |  yes     |  "None + Pending Out"    |
   |  "Both"                  |  yes     |  "To"                    |
   +----------------------------------------------------------------+






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9.4 Server Handling of Inbound Presence, Categorized by Subscription
    State

   This section defines how a server MUST handle an inbound presence
   stanza of type "subscribe", "subscribed", "unsubscribe", and
   "unsubscribed" (i.e., deliver it to the intended recipient and/or
   make a change to the subscription state), categorized by subscription
   state. (Note: some of the presence stanza types should never be
   received as inbound stanzas, since the sender's server MUST NOT route
   them to the intended recipient; however, these stanza types are
   included for the sake of completeness.)

9.4.1 Subscription State = None

   +--------------------------------------------------------+
   |  STANZA TYPE   |  DELIVER?  |  NEW STATE               |
   +--------------------------------------------------------+
   |  subscribe     |  yes       |  "None + Pending In"     |
   |  subscribed    |  no        |  no state change         |
   |  unsubscribe   |  no        |  no state change         |
   |  unsubscribed  |  no        |  no state change         |
   +--------------------------------------------------------+


9.4.2 Subscription State = None + Pending Out

   +--------------------------------------------------------+
   |  STANZA TYPE   |  DELIVER?  |  NEW STATE               |
   +--------------------------------------------------------+
   |  subscribe     |  yes       |  "None + Pending Out/In" |
   |  subscribed    |  yes       |  "To"                    |
   |  unsubscribe   |  no        |  no state change         |
   |  unsubscribed  |  yes       |  "None"                  |
   +--------------------------------------------------------+


9.4.3 Subscription State = None + Pending In

   +--------------------------------------------------------+
   |  STANZA TYPE   |  DELIVER?  |  NEW STATE               |
   +--------------------------------------------------------+
   |  subscribe     |  no        |  no state change         |
   |  subscribed    |  no        |  no state change         |
   |  unsubscribe   |  yes       |  "None"                  |
   |  unsubscribed  |  no        |  no state change         |
   +--------------------------------------------------------+





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9.4.4 Subscription State = None + Pending Out/In

   +--------------------------------------------------------+
   |  STANZA TYPE   |  DELIVER?  |  NEW STATE               |
   +--------------------------------------------------------+
   |  subscribe     |  no        |  no state change         |
   |  subscribed    |  yes       |  "To + Pending In"       |
   |  unsubscribe   |  yes       |  "None + Pending Out"    |
   |  unsubscribed  |  yes       |  "None + Pending In"     |
   +--------------------------------------------------------+


9.4.5 Subscription State = To

   +--------------------------------------------------------+
   |  STANZA TYPE   |  DELIVER?  |  NEW STATE               |
   +--------------------------------------------------------+
   |  subscribe     |  yes       |  "To + Pending In"       |
   |  subscribed    |  no        |  no state change         |
   |  unsubscribe   |  no        |  no state change         |
   |  unsubscribed  |  yes       |  "None"                  |
   +--------------------------------------------------------+


9.4.6 Subscription State = To + Pending In

   +--------------------------------------------------------+
   |  STANZA TYPE   |  DELIVER?  |  NEW STATE               |
   +--------------------------------------------------------+
   |  subscribe     |  no        |  no state change         |
   |  subscribed    |  no        |  no state change         |
   |  unsubscribe   |  yes       |  "To"                    |
   |  unsubscribed  |  yes       |  "None + Pending In"     |
   +--------------------------------------------------------+


9.4.7 Subscription State = From

   +--------------------------------------------------------+
   |  STANZA TYPE   |  DELIVER?  |  NEW STATE               |
   +--------------------------------------------------------+
   |  subscribe     |  no        |  no state change         |
   |  subscribed    |  no        |  no state change         |
   |  unsubscribe   |  yes       |  "None"                  |
   |  unsubscribed  |  no        |  no state change         |
   +--------------------------------------------------------+





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9.4.8 Subscription State = From + Pending Out

   +--------------------------------------------------------+
   |  STANZA TYPE   |  DELIVER?  |  NEW STATE               |
   +--------------------------------------------------------+
   |  subscribe     |  no        |  no state change         |
   |  subscribed    |  yes       |  "Both"                  |
   |  unsubscribe   |  yes       |  "None + Pending Out"    |
   |  unsubscribed  |  yes       |  "From"                  |
   +--------------------------------------------------------+


9.4.9 Subscription State = Both

   +--------------------------------------------------------+
   |  STANZA TYPE   |  DELIVER?  |  NEW STATE               |
   +--------------------------------------------------------+
   |  subscribe     |  no        |  no state change         |
   |  subscribed    |  no        |  no state change         |
   |  unsubscribe   |  yes       |  "To"                    |
   |  unsubscribed  |  yes       |  "From"                  |
   +--------------------------------------------------------+


9.5 Server Handling of Inbound Presence, Categorized by Presence Type

   This section defines how a server MUST handle an inbound presence
   stanza of type "subscribe", "subscribed", "unsubscribe", and
   "unsubscribed" (i.e., deliver it to the intended recipient and/or
   make a change to the subscription state), categorized by presence
   type.

9.5.1 Subscribe

   +------------------------------------------------------------------+
   |  EXISTING STATE          |  DELIVER?  |  NEW STATE               |
   +------------------------------------------------------------------+
   |  "None"                  |  yes       |  "None + Pending In"     |
   |  "None + Pending Out"    |  yes       |  "None + Pending Out/In" |
   |  "None + Pending In"     |  no        |  no state change         |
   |  "None + Pending Out/In" |  no        |  no state change         |
   |  "To"                    |  yes       |  "To + Pending In"       |
   |  "To + Pending In"       |  no        |  no state change         |
   |  "From"                  |  no        |  no state change         |
   |  "From + Pending Out"    |  no        |  no state change         |
   |  "Both"                  |  no        |  no state change         |
   +------------------------------------------------------------------+




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9.5.2 Subscribed

   +------------------------------------------------------------------+
   |  EXISTING STATE          |  DELIVER?  |  NEW STATE               |
   +------------------------------------------------------------------+
   |  "None"                  |  no        |  no state change         |
   |  "None + Pending Out"    |  yes       |  "To"                    |
   |  "None + Pending In"     |  no        |  no state change         |
   |  "None + Pending Out/In" |  yes       |  "To + Pending In"       |
   |  "To"                    |  no        |  no state change         |
   |  "To + Pending In"       |  no        |  no state change         |
   |  "From"                  |  no        |  no state change         |
   |  "From + Pending Out"    |  yes       |  "Both"                  |
   |  "Both"                  |  no        |  no state change         |
   +------------------------------------------------------------------+


9.5.3 Unsubscribe

   +------------------------------------------------------------------+
   |  EXISTING STATE          |  DELIVER?  |  NEW STATE               |
   +------------------------------------------------------------------+
   |  "None"                  |  no        |  no state change         |
   |  "None + Pending Out"    |  no        |  no state change         |
   |  "None + Pending In"     |  yes       |  "None"                  |
   |  "None + Pending Out/In" |  yes       |  "None + Pending Out"    |
   |  "To"                    |  no        |  no state change         |
   |  "To + Pending In"       |  yes       |  "To"                    |
   |  "From"                  |  yes       |  "None"                  |
   |  "From + Pending Out"    |  yes       |  "None + Pending Out     |
   |  "Both"                  |  yes       |  "To"                    |
   +------------------------------------------------------------------+


9.5.4 Unsubscribed

   +------------------------------------------------------------------+
   |  EXISTING STATE          |  DELIVER?  |  NEW STATE               |
   +------------------------------------------------------------------+
   |  "None"                  |  no        |  no state change         |
   |  "None + Pending Out"    |  yes       |  "None"                  |
   |  "None + Pending In"     |  no        |  no state change         |
   |  "None + Pending Out/In" |  yes       |  "None + Pending In"     |
   |  "To"                    |  yes       |  "None"                  |
   |  "To + Pending In"       |  yes       |  "None + Pending In"     |
   |  "From"                  |  no        |  no state change         |
   |  "From + Pending Out"    |  yes       |  "From"                  |
   |  "Both"                  |  yes       |  "From"                  |



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   +------------------------------------------------------------------+


9.6 Server Delivery and Client Acknowledgement of Subscription State
    Change Notifications

   When a server receives an inbound presence of type "subscribe",
   "subscribed", "unsubscribe", and "unsubscribed" that consists of a
   subscription state change notification, in addition to sending the
   appropriate "roster push" (or updated roster when the roster is next
   requested), it MUST deliver the notification to the intended
   recipient at least once.

   A server MUST require the recipient to approve or refuse a
   subscription request (i.e., an inbound presence stanza of type
   "subscribe") and MAY require the recipient to acknowledge receipt of
   the state change notification. In order to require acknowledgement, a
   server SHOULD send the notification to the recipient each time the
   recipient logs in, until the recipient acknowledges receipt of the
   notification by "affirming" or "denying" the notification, as shown
   in the following table:

   +--------------------------------------------------+
   |  NOTIFICATION  |  ACCEPT        |  DENY          |
   +--------------------------------------------------+
   |  subscribe     |  subscribed    |  unsubscribed  |
   |  subscribed    |  subscribe     |  unsubscribe   |
   |  unsubscribe   |  unsubscribed  |  subscribed    |
   |  unsubscribed  |  unsubscribe   |  subscribe     |
   +--------------------------------------------------+

   Obviously, given the foregoing subscription state charts, some the
   acknowledgement and denial stanzas will be routed to the contact and
   result in subscription state changes, while others will not. However,
   any such stanzas MUST result in the server's no longer sending the
   subscription state notification to the user.

   Because the sender's server MUST automatically generate outbound
   presence stanzas of type "unsubscribe" and "unsubscribed" upon
   receiving a roster set with the 'subscription' attribute set to a
   value of "remove" (see Removing a Roster Item and Cancelling All
   Subscriptions (Section 8.6)) the server MUST treat a roster remove
   request as equivalent to sending those presence stanzas for purposes
   of determining whether to continue sending subscription state change
   notifications of type "subscribe" or "subscribed" to the user.






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10. Blocking Communication

   Most instant messaging systems have found it necessary to implement
   some method for users to block communications from particular other
   users (this is also required by sections 5.1.5, 5.1.15, 5.3.2, and
   5.4.10 of RFC 2779 [2]). In XMPP this is done using the
   'jabber:iq:privacy' namespace by managing one's privacy lists.

   Server-side privacy lists enable successful completion of the
   following use cases:

   o  Retrieving one's privacy lists.

   o  Adding, removing, and editing one's privacy lists.

   o  Setting, changing, or declining active lists.

   o  Setting, changing, or declining the default list (i.e., the list
      that is active by default).

   o  Allowing or blocking messages based on JID, group, or subscription
      type (or globally).

   o  Allowing or blocking inbound presence notifications based on JID,
      group, or subscription type (or globally).

   o  Allowing or blocking outbound presence notifications based on JID,
      group, or subscription type (or globally).

   o  Allowing or blocking IQs based on JID, group, or subscription type
      (or globally).

   o  Allowing or blocking all communications based on JID, group, or
      subscription type (or globally).

   Note: presence notifications do not include presence subscriptions,
   only presence information that is broadcasted to entities that are
   subscribed to a user's presence information. Thus this includes
   presence stanzas with no 'type' attribute or of type='unavailable'
   only.

10.1 Syntax and Semantics

   A user MAY define one or more privacy lists, which are stored by the
   user's server. Each <list/> element contains one or more rules in the
   form of <item/> elements, and each <item/> element uses attributes to
   define a privacy rule type, a specific value to which the rules
   applies, the relevant action, and the place of the item in the



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   processing order.

   The syntax is as follows:

   <iq>
     <query xmlns='jabber:iq:privacy'>
       <list name='foo'>
         <item
             type='[jid|group|subscription]'
             value='bar'
             action='[accept|deny]'
             order='unsignedInt'/>
       </list>
     </query>
   </iq>

   If the type is "jid", then the 'value' attribute MUST contain a valid
   Jabber ID. JIDs are matched in the following order: <user@somedomain/
   resource>, then <user@somedomain>, then <somedomain/resource>, then
   <somedomain>. If the value is <user@somedomain>, then any connected
   resource for that user@somedomain matches. If the value is
   <somedomain/resource>, then only that resource matches. If the value
   is <somedomain>, then any user@somedomain (or subdomain) matches.

   If the type is "group", then the 'value' attribute SHOULD contain the
   name of a group in the user's roster. (If a client attempts to
   update, create, or delete a list item with a group that is not in the
   user's roster, the server SHOULD return to the client an
   <item-not-found/> stanza error.)

   If the type is "subscription", then the 'value' attribute MUST be one
   of "both", "to", "from", or "none" as defined in XMPP Core [1] and
   described under Managing One's Roster (Section 7).

   If no 'type' attribute is included, the rule provides the
   "fall-through" case.

   The 'action' attribute MUST be included and its value MUST be either
   "accept" or "deny".

   The 'order' attribute MUST be included and its value MUST be a
   non-negative integer that is unique among all items in the list. (If
   a client attempts to create or update a list with non-unique order
   values, the server MUST return to the client a <bad-request/> stanza
   error.

   Within the 'jabber:iq:privacy' namespace, the <query/> child of a
   client-generated IQ stanza of type "set" MUST NOT include more than



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   one child element (i.e., the stanza must contain only one <active/>
   element, one <default/> element, or one <list/> element); if a client
   violates this rule, the server MUST return to the client a
   <bad-request/> stanza error.)

   When a client adds or updates a privacy list, the <list/> element
   SHOULD contain at least one <item/> child element; when a client
   removes a privacy list, the <list/> element SHOULD contain no <item/>
   child element.

   When a client updates a privacy list, it must include all of the
   desired items (i.e., not a "delta").

10.2 Business Rules

   1.  If there is an active list set for a session, it affects only the
       session for which it is activated, and only for the duration of
       the session. Only the active list for that session is processed
       (i.e., the default list is ignored).

   2.  The default list applies to the user as a whole, and is processed
       if there is no active list set for the target session/resource to
       which a stanza is addressed, or if there are no current sessions
       for the user.

   3.  If there is no active list set for a session (or there are no
       current sessions for the user), and there is no default list,
       then all stanzas SHOULD BE accepted or appropriately processed by
       the server on behalf of the user.

   4.  Privacy lists MUST be the first rule applied by a server,
       superseding (1) the routing and delivery rules specified in
       Server Rules for Handling XML Stanzas (Section 14), and (2) the
       handling of subscription-related presence stanzas (and
       corresponding generation of roster pushes) specified in
       Integration of Roster Items and Presence Subscriptions (Section
       8).

   5.  The order in which privacy list items are processed by the server
       is important. List items MUST be processed in ascending order
       determined by the values of the 'order' attribute for each <item/
       >.

   6.  As soon as a stanza is matched against a privacy list, the server
       SHOULD appropriately handle the stanza and cease processing.

   7.  If no fall-through item is provided in a list, the fall-through
       action is assumed to be "accept".



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   8.  If a user updates the definition for an active list, subsequent
       processing based on that active list MUST use the updated
       definition (for all resources to which that active list currently
       applies).

   9.  If a change to the subscription state or roster group of a roster
       item defined in an active list occurs during a user's session,
       subsequent processing based on that active list MUST take into
       account the changed state or group (for all resources to which
       that active list currently applies).


10.3 Retrieving One's Privacy Lists

   Example: Client requests names of privacy lists from server:

   <iq type='get' id='getlist1'>
     <query xmlns='jabber:iq:privacy'/>
   </iq>

   Example: Server sends names of privacy lists to client, preceded by
   active list and default list:

   <iq type='result' id='getlist1' to='romeo@example.net/orchard'>
     <query xmlns='jabber:iq:privacy'>
       <active name='private'/>
       <default name='public'/>
       <list name='public'/>
       <list name='private'/>
       <list name='special'/>
     </query>
   </iq>

   Example: Client requests a privacy list from server:

   <iq type='get' id='getlist2'>
     <query xmlns='jabber:iq:privacy'>
       <list name='public'/>
     </query>
   </iq>

   Example: Server sends a privacy list to client:

   <iq type='result' id='getlist2' to='romeo@example.net/orchard'>
     <query xmlns='jabber:iq:privacy'>
       <list name='public'>
         <item type='jid'
               value='tybalt@example.com'
               action='deny'
               order='1'/>
         <item action='allow' order='2'/>
       </list>
     </query>



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               action='deny'
               order='1'/>
         <item action='allow' order='2'/>
       </list>
     </query>
   </iq>

   Example: Client requests another privacy list from server:

   <iq type='get' id='getlist3'>
     <query xmlns='jabber:iq:privacy'>
       <list name='private'/>
     </query>
   </iq>

   Example: Server sends another privacy list to client:

   <iq type='result' id='getlist3' to='romeo@example.net/orchard'>
     <query xmlns='jabber:iq:privacy'>
       <list name='private'>
         <item type='subscription'
               value='both'
               action='allow'
               order='10'/>
         <item action='deny' order='15'/>
       </list>
     </query>
   </iq>

   Example: Client requests yet another privacy list from server:

   <iq type='get' id='getlist4'>
     <query xmlns='jabber:iq:privacy'>
       <list name='special'/>
     </query>
   </iq>

   Example: Server sends yet another privacy list to client:

   <iq type='result' id='getlist4' to='romeo@example.net/orchard'>
     <query xmlns='jabber:iq:privacy'>
       <list name='special'>
         <item type='jid'
               value='juliet@example.com'
               action='allow'
               order='6'/>
         <item type='jid'
               value='benvolio@example.org'
               action='allow'
               order='7'/>
         <item type='jid'
               value='mercutio@shakespeare.lit'
               action='allow'



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               action='allow'
               order='7'/>
         <item type='jid'
               value='mercutio@shakespeare.lit'
               action='allow'
               order='42'/>
         <item action='deny' order='666'/>
       </list>
     </query>
   </iq>

   In this example, the user has three lists: (1) 'public', which allows
   communications from everyone except one specific entity (this is the
   default list); (2) 'private', which allows communications only with
   contacts who have a bidirectional subscription with the user (this is
   the active list); and (3) 'special', which allows communications only
   with three specific entities.

   If the user attempts to retrieve a list but a list by that name does
   not exist, the server MUST return an <item-not-found> stanza error to
   the user:

   Example: Client attempts to retrieve non-existent list:

   <iq type='error' id='getlist5'>
     <query xmlns='jabber:iq:privacy'>
       <list name='The Empty Set'/>
     </query>
     <error type='cancel'>
       <item-not-found
           xmlns='urn:ietf:params:xml:ns:xmpp-stanzas'/>
     </error>
   </iq>

   The user is allowed to retrieve only one list at a time. If the user
   attempts to retrieve more than one list in the same request, the
   server MUST return a <bad request> stanza error to the user:

   Example: Client attempts to retrieve more than one list:

   <iq type='error' id='getlist6'>
     <query xmlns='jabber:iq:privacy'>
       <list name='public'/>
       <list name='private'/>
       <list name='special'/>
     </query>
     <error type='modify'>
       <bad-request
           xmlns='urn:ietf:params:xml:ns:xmpp-stanzas'/>
     </error>
   </iq>



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9.4


           xmlns='urn:ietf:params:xml:ns:xmpp-stanzas'/>
     </error>
   </iq>


10.4 Managing Active Lists

   In order to set or change the active list currently being applied by
   the server, the user MUST send an IQ stanza of type "set" with a
   <query/> element qualified by the 'jabber:iq:privacy' namespace that
   contains an empty <active/> child element possessing a 'name'
   attribute whose value is set to the desired list name.

   Example: Client requests change of active list:

   <iq type='set' id='active1'>
     <query xmlns='jabber:iq:privacy'>
       <active name='special'/>
     </query>
   </iq>

   The server MUST activate and apply the requested list before sending
   the result back to the client.

   Example: Server acknowledges success of active list change:

   <iq type='result' id='active1' to='juliet@example.com/balcony'/>

   If the user attempts to set an active list but a list by that name
   does not exist, the server MUST return an <item-not-found> stanza
   error to the user:

   Example: Client attempts to set a non-existent list as active:

   <iq type='error' id='active2'>
     <query xmlns='jabber:iq:privacy'>
       <active name='The Empty Set'/>
     </query>
     <error type='cancel'>
       <item-not-found
           xmlns='urn:ietf:params:xml:ns:xmpp-stanzas'/>
     </error>
   </iq>

   In order to decline the use of any active list, a user MUST send an
   empty <active/> element with no name.

   Example: Client declines the use of active lists:

   <iq type='set' id='active2'>
     <query xmlns='jabber:iq:privacy'>
       <active/>
     </query>



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   <iq type='set' id='active2'>
     <query xmlns='jabber:iq:privacy'>
       <active/>
     </query>
   </iq>


9.5


10.5 Managing the Default List

   In order to change its default list, the user MUST send an IQ stanza
   of type "set" with a <query/> element qualified by the
   'jabber:iq:privacy' namespace that contains an empty <default/> child
   element possessing a 'name' attribute whose value is set to the
   desired list name.

   Example: Client requests change of default list:

   <iq type='set' id='default1'>
     <query xmlns='jabber:iq:privacy'>
       <default name='special'/>
     </query>
   </iq>

   Example: Server acknowledges success of default list change:

   <iq type='result' id='default1' to='juliet@example.com/balcony'/>

   If the user attempts to set a default list but a list by that name
   does not exist, the server MUST return an <item-not-found> stanza
   error to the user:

   Example: Client attempts to set a non-existent list as default:

   <iq type='error' id='default2'>
     <query xmlns='jabber:iq:privacy'>
       <default name='The Empty Set'/>
     </query>
     <error type='cancel'>
       <item-not-found
           xmlns='urn:ietf:params:xml:ns:xmpp-stanzas'/>
     </error>
   </iq>

   In order to decline the use of a default list (i.e., to use the
   domain's stanza routing rules at all times), a user MUST send an
   empty <default/> element with no name.

   Example: Client declines the use of the default list:

   <iq type='set' id='default2'>
     <query xmlns='jabber:iq:privacy'>
       <default/>



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   <iq type='set' id='default2'>
     <query xmlns='jabber:iq:privacy'>
       <default/>
     </query>
   </iq>


9.6


10.6 Editing a Privacy List

   In order to edit a privacy list, the user MUST send an IQ stanza of
   type "set" with a <query/> element qualified by the
   'jabber:iq:privacy' namespace that contains one <list/> child element
   possessing a 'name' attribute whose value is set to the list name the
   user would like to edit. The <list/> element MUST contain one or more
   <item/> elements, which specify the user's desired changes to the
   list by including all elements in the list (not the "delta").

   Example: Client edits a privacy list:

   <iq type='set' id='edit1'>
     <query xmlns='jabber:iq:privacy'>
       <list name='public'>
         <item type='jid'
               value='tybalt@example.com'
               action='deny'
               order='3'/>
         <item type='jid'
               value='paris@example.org'
               action='deny'
               order='5'/>
         <item action='allow' order='68'/>
       </list>
     </query>
   </iq>

   Note: The value of the 'order' attribute for any given item is not
   fixed. Thus in the foregoing example if the user would like to add 4
   items between the "tybalt@example.com" item and the
   "paris@example.org" item, the user's client MUST renumber the
   relevant items before submitting the list to the server.

   Example: Server acknowledges success of list edit:

   <iq type='result' id='edit1' to='juliet@example.com/balcony'/>


9.7







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10.7 Adding a New Privacy List

   The same protocol used to edit an existing list is used to create a
   new list. If the list name matches that of an existing list, the
   request to add a new list will overwrite the old one.



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9.8

10.8 Removing a Privacy List

   In order to remove a privacy list, the user MUST send an IQ stanza of
   type "set" with a <query/> element qualified by the
   'jabber:iq:privacy' namespace that contains one empty <list/> child
   element possessing a 'name' attribute whose value is set to the list
   name the user would like to remove.

   Example: Client removes a privacy list:

   <iq type='set' id='remove1'>
     <query xmlns='jabber:iq:privacy'>
       <list name='private'/>
     </query>
   </iq>

   Example: Server acknowledges success of list removal:

   <iq type='result' id='remove1' to='juliet@example.com/balcony'/>

   If a user attempts to remove an active list or the default list, the
   server MUST return a <conflict/> stanza error to the user. The user
   MUST first set another list to active or default before removing it.

   If the user attempts to remove a list but a list by that name does
   not exist, the server MUST return an <item-not-found> stanza error to
   the user:

   If the user attempts to remove more than one list in the same
   request, the server MUST return a <bad request> stanza error to the
   user.

9.9

10.9 Blocking Messages

   Server-side privacy lists enable a user to block incoming messages
   from other users based on the other user's JID, roster group, or
   subscription status (or globally). The following examples illustrate
   the protocol.

   Example: User blocks based on JID:

   <iq type='set' id='msg1'>
     <query xmlns='jabber:iq:privacy'>
       <list name='message-jid-example'>
         <item type='jid'
               value='tybalt@example.com'
               action='deny'
               order='3'>



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     <query xmlns='jabber:iq:privacy'>
       <list name='message-jid-example'>
         <item type='jid'
               value='tybalt@example.com'
               action='deny'
               order='3'>
           <message/>
         </item>
       </list>
     </query>
   </iq>

   As a result of creating and applying the foregoing list, the user
   will not receive messages from the user with the specified JID.

   Example: User blocks based on roster group:

   <iq type='set' id='msg2'>
     <query xmlns='jabber:iq:privacy'>
       <list name='message-group-example'>
         <item type='group'
               value='Enemies'
               action='deny'
               order='4'>
           <message/>
         </item>
       </list>
     </query>
   </iq>

   As a result of creating and applying the foregoing list, the user
   will not receive messages from any users in the specified roster
   group.

   Example: User blocks based on subscription type:

   <iq type='set' id='msg3'>
     <query xmlns='jabber:iq:privacy'>
       <list name='message-sub-example'>
         <item type='subscription'
               value='none'
               action='deny'
               order='5'>
           <message/>
         </item>
       </list>
     </query>
   </iq>



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   As a result of creating and applying the foregoing list, the user
   will not receive messages from any users with the specified
   subscription type.

   Example: User blocks globally:



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   <iq type='set' id='msg4'>
     <query xmlns='jabber:iq:privacy'>
       <list name='message-global-example'>
         <item action='deny' order='6'>
           <message/>
         </item>
       </list>
     </query>
   </iq>

   As a result of creating and applying the foregoing list, the user
   will not receive messages from any other users.

9.10

10.10 Blocking Inbound Presence Notifications

   Server-side privacy lists enable a user to block incoming presence
   notifications from other users based on the other user's JID, roster
   group, or subscription status (or globally). The following examples
   illustrate the protocol.

   Note: presence notifications do not include presence subscriptions,
   only presence information that is broadcasted to the user because the
   user previously subscribed to a contact's presence information. Thus
   this includes presence stanzas with no 'type' attribute or of
   type='unavailable' only.

   Example: User blocks based on JID:

   <iq type='set' id='presin1'>
     <query xmlns='jabber:iq:privacy'>
       <list name='presin-jid-example'>
         <item type='jid'
               value='tybalt@example.com'
               action='deny'
               order='7'>
           <presence-in/>
         </item>
       </list>
     </query>
   </iq>

   As a result of creating and applying the foregoing list, the user



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   will not receive presence notifications from the user with the
   specified JID.

   Example: User blocks based on roster group:

   <iq type='set' id='presin2'>



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     <query xmlns='jabber:iq:privacy'>
       <list name='presin-group-example'>
         <item type='group'
               value='Enemies'
               action='deny'
               order='8'>
           <presence-in/>
         </item>
       </list>
     </query>
   </iq>

   As a result of creating and applying the foregoing list, the user
   will not receive presence notifications from any users in the
   specified roster group.

   Example: User blocks based on subscription type:

   <iq type='set' id='presin3'>
     <query xmlns='jabber:iq:privacy'>
       <list name='presin-sub-example'>
         <item type='subscription'
               value='to'
               action='deny'
               order='9'>
           <presence-in/>
         </item>
       </list>
     </query>
   </iq>

   As a result of creating and applying the foregoing list, the user
   will not receive presence notifications from any users with the
   specified subscription type.

   Example: User blocks globally:

   <iq type='set' id='presin4'>
     <query xmlns='jabber:iq:privacy'>
       <list name='presin-global-example'>
         <item action='deny' order='11'>
           <presence-in/>



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         </item>
       </list>
     </query>
   </iq>

   As a result of creating and applying the foregoing list, the user



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   will not receive presence notifications from any other users.

9.11

10.11 Blocking Outbound Presence Notifications

   Server-side privacy lists enable a user to block outgoing presence
   notifications to other users based on the other user's JID, roster
   group, or subscription status (or globally). The following examples
   illustrate the protocol.

   Note: presence notifications do not include presence subscriptions,
   only presence information that is broadcasted to contacts because
   those contacts previously subscribed to the user's presence
   information. Thus this includes presence stanzas with no 'type'
   attribute or of type='unavailable' only. Note also that because
   information about last activity MAY be requested by a contact (as
   defined in Section 4.5), a user SHOULD block both outbound presence
   and IQs in relation that is broadcasted to any given entity. contacts because
   those contacts previously subscribed to the user's presence
   information. Thus this includes presence stanzas with no 'type'
   attribute or of type='unavailable' only.

   Example: User blocks based on JID:

   <iq type='set' id='presout1'>
     <query xmlns='jabber:iq:privacy'>
       <list name='presout-jid-example'>
         <item type='jid'
               value='tybalt@example.com'
               action='deny'
               order='13'>
           <presence-out/>
         </item>
       </list>
     </query>
   </iq>

   As a result of creating and applying the foregoing list, the user
   will not send presence notifications to the user with the specified
   JID.

   Example: User blocks based on roster group:

   <iq type='set' id='presout2'>
     <query xmlns='jabber:iq:privacy'>
       <list name='presout-group-example'>
         <item type='group'
               value='Enemies'
               action='deny'
               order='15'>
           <presence-out/>
         </item>



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               order='15'>
           <presence-out/>
         </item>
       </list>
     </query>
   </iq>

   As a result of creating and applying the foregoing list, the user
   will not send presence notifications to any users in the specified
   roster group.

   Example: User blocks based on subscription type:

   <iq type='set' id='presout3'>
     <query xmlns='jabber:iq:privacy'>
       <list name='presout-sub-example'>
         <item type='subscription'
               value='from'
               action='deny'
               order='17'>
           <presence-out/>
         </item>
       </list>
     </query>
   </iq>

   As a result of creating and applying the foregoing list, the user
   will not send presence notifications to any users with the specified
   subscription type.

   Example: User blocks globally:

   <iq type='set' id='presout4'>
     <query xmlns='jabber:iq:privacy'>
       <list name='presout-global-example'>
         <item action='deny' order='23'>
           <presence-out/>
         </item>
       </list>
     </query>
   </iq>

   As a result of creating and applying the foregoing list, the user
   will not send presence notifications to any other users.

9.12

10.12 Blocking IQs

   Server-side privacy lists enable a user to block incoming IQ requests



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   of type "get" or "set" from other users based on the other user's
   JID, roster group, or subscription status (or globally). The
   following examples illustrate the protocol.



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   Example: User blocks based on JID:

   <iq type='set' id='iq1'>
     <query xmlns='jabber:iq:privacy'>
       <list name='iq-jid-example'>
         <item type='jid'
               value='tybalt@example.com'
               action='deny'
               order='29'>
           <iq/>
         </item>
       </list>
     </query>
   </iq>

   As a result of creating and applying the foregoing list, the user
   will not receive IQ requests of type "get" or "set" from the user
   with the specified JID.

   Example: User blocks based on roster group:

   <iq type='set' id='iq2'>
     <query xmlns='jabber:iq:privacy'>
       <list name='iq-group-example'>
         <item type='group'
               value='Enemies'
               action='deny'
               order='31'>
           <iq/>
         </item>
       </list>
     </query>
   </iq>

   As a result of creating and applying the foregoing list, the user
   will not receive IQ requests of type "get" or "set" from any users in
   the specified roster group.

   Example: User blocks based on subscription type:

   <iq type='set' id='iq3'>
     <query xmlns='jabber:iq:privacy'>
       <list name='iq-sub-example'>
         <item type='subscription'
               value='none'
               action='deny'
               order='17'>
           <iq/>



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               value='none'
               action='deny'
               order='17'>
           <iq/>
         </item>
       </list>
     </query>
   </iq>

   As a result of creating and applying the foregoing list, the user
   will not receive IQ requests of type "get" or "set" from any users
   with the specified subscription type.

   Example: User blocks globally:

   <iq type='set' id='iq4'>
     <query xmlns='jabber:iq:privacy'>
       <list name='iq-global-example'>
         <item action='deny' order='1'>
           <iq/>
         </item>
       </list>
     </query>
   </iq>

   As a result of creating and applying the foregoing list, the user
   will not receive IQ requests of type "get" or "set" from any other
   users.

9.13

10.13 Blocking All Communication

   Server-side privacy lists enable a user to block all communications stanzas from and presence
   to other users based on the other user's JID, roster group, or
   subscription status (or globally). Note that this includes
   subscription-related presence stanzas, which are excluded by Blocking
   Inbound Presence Notifications (Section 10.10). The following
   examples illustrate the protocol.

   Example: User blocks based on JID:

   <iq type='set' id='all1'>
     <query xmlns='jabber:iq:privacy'>
       <list name='all-jid-example'>
         <item type='jid'
               value='tybalt@example.com'
               action='deny'
               order='23'/>
       </list>



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     </query>
   </iq>

   As a result of creating and applying the foregoing list, the user
   will not receive any communications from, nor send any stanzas to,
   the user with the specified JID.



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   Example: User blocks based on roster group:

   <iq type='set' id='all2'>
     <query xmlns='jabber:iq:privacy'>
       <list name='all-group-example'>
         <item type='group'
               value='Enemies'
               action='deny'
               order='13'/>
       </list>
     </query>
   </iq>

   As a result of creating and applying the foregoing list, the user
   will not receive any communications from, nor send any stanzas to,
   any users in the specified roster group.

   Example: User blocks based on subscription type:

   <iq type='set' id='all3'>
     <query xmlns='jabber:iq:privacy'>
       <list name='all-sub-example'>
         <item type='subscription'
               value='none'
               action='deny'
               order='11'/>
       </list>
     </query>
   </iq>

   As a result of creating and applying the foregoing list, the user
   will not receive any communications from, nor send any stanzas to,
   any users with the specified subscription type.

   Example: User blocks globally:

   <iq type='set' id='all4'>
     <query xmlns='jabber:iq:privacy'>
       <list name='all-global-example'>
         <item action='deny' order='7'/>
       </list>



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     </query>
   </iq>

   As a result of creating and applying the foregoing list, the user
   will not receive any communications from, nor send any stanzas to,
   any other users.




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9.14

10.14 Blocked Entity Attempts to Communicate with User

   If a blocked entity attempts to send messages or presence
   notifications to the user, the user's server SHOULD silently drop the
   stanza and MUST NOT return an error to the sending entity.

   If a blocked entity attempts to send an IQ stanza of type "get" or
   "set" to the user, the user's server MUST return to the sending
   entity a <feature-not-implemented/> stanza error, since this is the
   standard error code sent from a client that does not understand the
   namespace of an IQ get or set. IQ stanzas of other types SHOULD be
   silently dropped by the server.

   Example: Blocked entity attempts to send IQ get:

   <iq type='get'
       to='romeo@example.net'
       from='tybalt@example.com/pda'
       id='probing1'>
     <query xmlns='jabber:iq:last'/> xmlns='jabber:iq:version'/>
   </iq>

   Example: Server returns error to blocked entity:

   <iq type='error'
       from='romeo@example.net'
       to='tybalt@example.com/pda'
       id='probing1'>
     <query xmlns='jabber:iq:last'/> xmlns='jabber:iq:version'/>
     <error type='cancel'>
       <feature-not-implemented
           xmlns='urn:ietf:params:xml:ns:xmpp-stanzas'/>
     </error>
   </iq>


9.15


10.15 Higher-Level Heuristics

   When building a representation of a higher-level privacy heuristic, a
   client SHOULD use the simplest possible representation.




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   For example, the heuristic "block all communications with any user
   not in my roster" could be constructed in any of the following ways:

   o  allow communications from all JIDs in my roster (i.e., listing
      each JID as a separate list item), but block communications with
      everyone else




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   o  allow communications from any user who is in one of the groups
      that make up my roster (i.e., listing each group as a separate
      list item), but block communications from everyone else

   o  allow communications from any user with whom I have a subscription
      of 'both' or 'to' or 'from' (i.e., listing each subscription value
      separately), but block communications from everyone else

   o  block communications from anyone whose subscription state is
      'none'

   The final representation is the simplest and SHOULD be used; here is
   the XML that would be sent that would be sent in this case:

   <iq type='set' id='heuristic1'>
     <query xmlns='jabber:iq:privacy'>
       <list name='heuristic-example'>
         <item type='subscription'
               value='none'
               action='deny'
               order='437'/>
       </list>
     </query>
   </iq>




















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11. IANA Considerations

   For several related IANA considerations, refer to XMPP Core [1].

11.1 XML Namespace Name for Session Data

   A URN sub-namespace for session-related data in the Extensible
   Messaging and Presence Protocol (XMPP) is defined as follows.

   URI: urn:ietf:params:xml:ns:xmpp-session

   Specification: [RFCXXXX]

   Description: This is the XML namespace name for session-related data
      in this case:

   <iq type='set' id='heuristic1'>
     <query xmlns='jabber:iq:privacy'>
       <list name='heuristic-example'>
         <item type='subscription'
               value='none'
               action='deny'
               order='437'/>
       </list>
     </query>
   </iq> the Extensible Messaging and Presence Protocol (XMPP) as
      defined by [RFCXXXX].

   Registrant Contact: IETF, XMPP Working Group, <xmppwg@jabber.org>

































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10. Server Rules for Handling XML Stanzas

   Each server implementation will contain its own "delivery tree" for
   handling stanzas it receives. Such a tree determines whether a stanza
   needs to be routed to another domain, processed internally, or
   delivered to a connected resource associated with a registered user.
   The following rules apply:

10.1 No 'to' Address

   If the stanza possesses no 'to' attribute, the server SHOULD process
   it on behalf of the entity that sent it. Because all stanzas received
   from other servers MUST possess a 'to' attribute, this rule applies
   only to stanzas received from an entity that is connected to the
   server (usually an active client session). If the server receives a
   presence stanza with no 'to' attribute, the server SHOULD broadcast
   it to the entities that are subscribed


12. Internationalization Considerations

   For internationalization considerations, refer to the sending entity's
   presence as defined under Section 4.1. If the server receives an IQ
   stanza of type "get" or "set" with no 'to' attribute and it
   understands the namespace that qualifies the content of the stanza,
   it MUST process the stanza on behalf of sending entity (where the
   meaning of "process" is determined by the semantics relevant
   section of XMPP Core [1].















































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13. Security Considerations

   Core security considerations for XMPP are defined in the qualifying
   namespace).

10.2 Foreign Domain

   If the hostname relevant
   section of the domain identifier portion XMPP Core [1].

   Additional considerations that apply only to instant messaging and
   presence applications of the JID contained XMPP are defined in the 'to' attribute does not match several places within
   this document; specifically:

   o  When a server processes a stanza of any kind whose intended
      recipient is a user associated with one of the configured hostnames
   of server's hostnames,
      the server itself or MUST first apply any privacy rules (Section 10) that
      are in force (see Server Rules for Handling XML Stanzas (Section
      14)).

   o  When a subdomain thereof, the server SHOULD route
   the processes an inbound presence stanza to the foreign domain (subject to local service
   provisioning and security policies regarding inter-domain
   communication). If routing to the recipient's server of type "probe"
      whose intended recipient is unsuccessful, a user associated with one of the
      server's hostnames, the sender's server MUST return an error to NOT reveal the sender; user's presence
      information if the
   recipient's server can be contacted but delivery by the recipient's
   server to the recipient sender is unsuccessful, the recipient's server MUST
   return an error a user who is not authorized to the sender
      receive that information as determined by way of the sender's server.

10.3 Subdomain

   If the hostname of the domain identifier portion of the JID contained
   in the 'to' attribute matches presence subscriptions
      (see Client and Server Presence Responsibilities (Section 5.1)).

   o  When a subdomain of one of the configured
   hostnames of the server itself, the server MAY process the processes an outbound presence stanza
   itself with no type
      or MAY route of type "unavailable", it MUST follow the stanza rules defined under
      Client and Server Presence Responsibilities (Section 5.1) in order
      to a specialized service ensure that such presence information is
   responsible for not broadcasted to
      entities that subdomain (if any).

10.4 Bare Domain or Specific Resource

   If the hostname of the domain identifier portion of the JID contained are not authorized to know such information.
























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   in the 'to' attribute matches the hostname of the server itself and
   the JID contained in the 'to' attribute is of the form <somedomain>
   or <somedomain/resource>, the server (or a


14. Server Rules for Handling XML Stanzas

   Basic delivery rules for servers are defined resource thereof)
   SHOULD process the stanza as appropriate in XMPP Core [1]. This
   section defines additional rules for the stanza type. If the
   stanza is an IQ stanza and the server understands the namespace that
   qualifies the content of the stanza, the server SHOULD process the
   request according to the semantics of the qualifying namespace, instant messaging and
   MUST reply with an IQ of type "result" or "error".

10.5 User in Same Domain presence
   applications.

   If the hostname of the domain identifier portion of the JID contained
   in the 'to' attribute of a stanza matches the hostname of the server
   itself and the JID contained in the 'to' attribute is of the form
   <user@somedomain> or <user@somedomain/resource>, the server SHOULD MUST
   first apply any privacy rules (Section 9) 10) that are in force. If
   privacy rules allow the stanza, it SHOULD be routed or delivered to
   the intended recipient of the stanza as represented by the JID
   contained in the 'to' attribute. The following additional rules apply:

   1.  If the JID contains a resource identifier (i.e., is of the form
       <user@somedomain/resource>) and there is an available resource
       whose authzid matches the full JID, the recipient's server SHOULD
       deliver the stanza apply
   to the session that exactly matches the
       resource identifier.

   2.  If the JID contains a resource identifier instant messaging and there is no
       available resource whose authzid matches the full JID, the
       recipient's server SHOULD return to the sender a
       <recipient-unavailable/> stanza error.

   3. presence applications, over and above those
   defined in XMPP Core [1]:

   1.  If the JID is of the form <user@somedomain> and there is at least
       one available resource available for the user, the recipient's
       server MUST follow these rules:

       1.  For message stanzas, the server SHOULD deliver the stanza to
           the available resource that provided the highest value for
           the <priority/> element (if the resource did not provide a
           priority, the server SHOULD consider it to have provided a
           value of zero). If two resources have the same priority, the
           server MAY use some other rule (e.g., most recent connect
           time or activity time) to choose between them. However, the
           server MUST NOT deliver the stanza to an available resource
           that provided a negative value for the <priority/> element.

       2.  For presence stanzas other than those of type "probe", the
           server MUST deliver the stanza to all available resources,
           except that the server MUST NOT deliver the stanza to an



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           available resource that provided a negative value for the
           <priority/> element; for presence probes, the server SHOULD
           reply based on the rules defined in Section 4.1. Client and Server
           Presence Responsibilities (Section 5.1).

       3.  For IQ stanzas, the server itself MUST reply on behalf of the
           user with either an IQ result or an IQ error, and MUST NOT
           deliver the IQ stanza to any of the available resources.
           Specifically, if the semantics of the qualifying namespace
           define a reply that the server can provide, the server MUST
           reply to the stanza on behalf of the user (e.g., this is the
           case with the 'jabber:iq:last' protocol defined above); user; if not, the server
           MUST reply with a <service-unavailable/> stanza error.

   4.





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   2.  If the JID is of the form <user@somedomain> and there are no
       available resources associated with the user (e.g., an instant
       messaging user is offline), how the stanza is handled depends on
       the stanza type:

       1.  For presence stanzas of type "subscribe", the server MUST
           maintain a record of the stanza, as specified under Section
           4.1. Client
           and Server Presence Responsibilities (Section 5.1).

       2.  For all other presence stanzas, the server SHOULD silently
           ignore the stanza by not storing it for later delivery or
           replying to it on behalf of the user.

       3.  For message stanzas, the server MAY choose to store the
           stanza on behalf of the user and deliver it when the user
           next becomes available. However, if offline message storage
           is not enabled, the server MUST return to the sender a
           <service-unavailable/> stanza error. (Note: offline message
           storage is not defined in XMPP since it strictly is a matter
           of implementation and service provisioning.)

       4.  For IQ stanzas, the server itself MUST reply on behalf of the
           user with either an IQ result or an IQ error. Specifically,
           if the semantics of the qualifying namespace define a reply
           that the server can provide, the server MUST reply to the
           stanza on behalf of the user (e.g., this is user; if not, the case server MUST reply
           with a <service-unavailable/> stanza error.
























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15. Compliance Requirements

   This section summarizes the
           'jabber:iq:last' protocol specific aspects of the Extensible
   Messaging and Presence Protocol that MUST be supported by instant
   messaging servers and client in order to be considered compliant
   implementations. All such applications MUST comply with the
   requirements specified in XMPP Core [1]. The text in this section
   specifies additional compliance requirements for instant messaging
   servers and clients; the requirements described here supplement but
   do not supersede the core requirements.

15.1 Servers

   In addition to core server compliance requirements, an instant
   messaging and presence application server MUST additionally support
   the following IM-related protocols:

   o  All server-related instant messaging syntax and semantics defined
      in this document, including presence broadcast on behalf of
      clients, presence subscriptions, roster storage and manipulation,
      privacy rules, and IM-specific routing and delivery rules


15.2 Clients

   In addition to core client compliance requirements, an instant
   messaging client MUST additionally support the following IM-related
   protocols:

   o  Generation and handling of the IM-specific semantics of XML
      stanzas as defined by the XML schemas, including the 'type'
      attribute of message and presence stanzas as well as their child
      elements

   o  All client-related instant messaging syntax and semantics defined
      in this document, including presence subscriptions, roster
      management, and privacy rules

   o  End-to-end object encryption as defined above); if not, the server
           MUST reply with a <service-unavailable/> stanza error. in XMPP e2e [6]












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11. IANA Considerations

   For several related IANA considerations, refer to XMPP Core [1].

11.1 XML Namespace Name for Session Data

   A URN sub-namespace for session-related data


Normative References

   [1]  Saint-Andre, P. and J. Miller, "XMPP Core",
        draft-ietf-xmpp-core-18 (work in the Extensible
   Messaging progress), September 2003.

   [2]  Day, M., Aggarwal, S. and J. Vincent, "Instant Messaging /
        Presence Protocol (XMPP) is defined as follows.

   URI: urn:ietf:params:xml:ns:xmpp-session

   Specification: [RFCXXXX]

   Description: This is the XML namespace name Requirements", RFC 2779, February 2000.

   [3]  World Wide Web Consortium, "Extensible Markup Language (XML) 1.0
        (Second Edition)", W3C xml, October 2000, <http://www.w3.org/TR/
        2000/REC-xml-20001006>.

   [4]  World Wide Web Consortium, "Namespaces in XML", W3C xml-names,
        January 1999, <http://www.w3.org/TR/1999/REC-xml-names-19990114/
        >.

   [5]  Bradner, S., "Key words for session-related data use in the Extensible Messaging and Presence Protocol (XMPP) as
      defined by [RFCXXXX].

   Registrant Contact: IETF, XMPP Working Group, <xmppwg@jabber.org> RFCs to Indicate Requirement
        Levels", BCP 14, RFC 2119, March 1997.

   [6]  Saint-Andre, P., "End-to-End Object Encryption in XMPP",
        draft-ietf-xmpp-e2e-05 (work in progress), August 2003.






























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12. Security Considerations

   For security considerations, refer to the relevant section of XMPP
   Core [1].


Informative References

   [7]  Jabber Software Foundation, "Jabber Software Foundation",
        <http://www.jabber.org/>.

   [8]  Day, M., Rosenberg, J. and H. Sugano, "A Model for Presence and
        Instant Messaging", RFC 2778, February 2000, <http://
        www.ietf.org/rfc/rfc2778.txt>.

   [9]  Dawson, F. and T. Howes, "vCard MIME Directory Profile", RFC
        2426, September 1998.


Authors' Addresses

   Peter Saint-Andre
   Jabber Software Foundation

   EMail: stpeter@jabber.org


   Jeremie Miller
   Jabber Software Foundation

   EMail: jeremie@jabber.org


























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13. Compliance Requirements

   This section summarizes the specific aspects of the Extensible 96]

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Appendix A. vCards

   Sections 3.1.3 and Presence Protocol 4.1.4 of RFC 2779 [2] require that MUST it be supported by instant
   messaging servers and client in order possible
   to be considered compliant
   implementations. All such applications MUST comply with the
   requirements specified in XMPP Core [1]. The text in this section
   specifies additional compliance requirements retrieve out-of-band contact information for instant messaging
   servers and clients; the requirements described here supplement but
   do not supersede the core requirements.

13.1 Servers

   In addition to core server compliance requirements, an instant
   messaging application server MUST additionally support other users (e.g.,
   telephone number or email address). An XML representation of the following
   IM-related protocols:

   o  All server-related instant messaging syntax and semantics
   vCard specification defined in this document, including presence broadcast on behalf of
      clients, presence subscriptions, roster storage and manipulation,
      privacy rules, and IM-specific routing and delivery rules


13.2 Clients

   In addition to core client compliance requirements, an instant
   messaging client MUST additionally support the following IM-related
   protocols:

   o  Generation and handling of RFC 2426 [9] is in common use within
   the IM-specific semantics Jabber community to provide such information but is out of XML
      stanzas as defined by the XML schemas, including the 'type'
      attribute scope
   for XMPP (documentation of message and presence stanzas as well as their child
      elements

   o  All client-related instant messaging syntax and semantics defined
      in this document, including presence subscriptions, roster
      management, and privacy rules

   o  End-to-end object encryption as defined protocol is contained in "JEP-0054:
   vcard-temp", published by the Jabber Software Foundation [7]).










































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Appendix B. XML Schemas

   The following XML schemas are descriptive, not normative. For schemas
   defining the core features of XMPP, refer to XMPP e2e [4] Core [1].

B.1 jabber:client namespace

   <?xml version='1.0' encoding='UTF-8'?>

   <xs:schema
       xmlns:xs='http://www.w3.org/2001/XMLSchema'
       xmlns:xml='http://www.w3.org/XML/1998/namespace'
       targetNamespace='jabber:client'
       xmlns='jabber:client'
       elementFormDefault='qualified'>

     <xs:import namespace='http://www.w3.org/XML/1998/namespace'
                schemaLocation='http://www.w3.org/2001/xml.xsd'/>

     <xs:element name='message'>
        <xs:complexType>
           <xs:sequence>
              <xs:element ref='subject'
                          minOccurs='0'
                          maxOccurs='unbounded'/>
              <xs:element ref='body'
                          minOccurs='0'
                          maxOccurs='unbounded'/>
              <xs:element ref='thread'
                          minOccurs='0'
                          maxOccurs='1'/>
              <xs:any     namespace='##other'
                          minOccurs='0'
                          maxOccurs='unbounded'/>
              <xs:element ref='error'
                          minOccurs='0'
                          maxOccurs='1'/>
           </xs:sequence>
           <xs:attribute name='to'
                         type='xs:string'
                         use='optional'/>
           <xs:attribute name='from'
                         type='xs:string'
                         use='optional'/>
           <xs:attribute name='id'
                         type='xs:NMTOKEN'
                         use='optional'/>
           <xs:attribute ref='xml:lang' use='optional'/>



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           <xs:attribute name='type' use='optional'>
             <xs:simpleType>
               <xs:restriction base='xs:NCName'>
                 <xs:enumeration value='chat'/>
                 <xs:enumeration value='error'/>
                 <xs:enumeration value='groupchat'/>
                 <xs:enumeration value='headline'/>
                 <xs:enumeration value='normal'/>
               </xs:restriction>
             </xs:simpleType>
           </xs:attribute>
        </xs:complexType>
     </xs:element>

     <xs:element name='body' type='xs:string'>
       <xs:complexType>
         <xs:attribute ref='xml:lang' use='optional'/>
       </xs:complexType>
     </xs:element>

     <xs:element name='subject' type='xs:string'>
       <xs:complexType>
         <xs:attribute ref='xml:lang' use='optional'/>
       </xs:complexType>
     </xs:element>

     <xs:element name='thread' type='xs:NMTOKEN'/>

     <xs:element name='presence'>
       <xs:complexType>
         <xs:sequence>
           <xs:element ref='show'
                       minOccurs='0'
                       maxOccurs='1'/>
           <xs:element ref='status'
                       minOccurs='0'
                       maxOccurs='unbounded'/>
           <xs:element ref='priority'
                       minOccurs='0'
                       maxOccurs='1'/>
           <xs:any     namespace='##other'
                       minOccurs='0'
                       maxOccurs='unbounded'/>
           <xs:element ref='error'
                       minOccurs='0'
                       maxOccurs='1'/>
         </xs:sequence>
         <xs:attribute name='to'



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                       type='xs:string'
                       use='optional'/>
         <xs:attribute name='from'
                       type='xs:string'
                       use='optional'/>
         <xs:attribute name='id'
                       type='xs:NMTOKEN'
                       use='optional'/>
         <xs:attribute ref='xml:lang' use='optional'/>
         <xs:attribute name='type' use='optional'>
           <xs:simpleType>
             <xs:restriction base='xs:NCName'>
               <xs:enumeration value='subscribe'/>
               <xs:enumeration value='subscribed'/>
               <xs:enumeration value='unsubscribe'/>
               <xs:enumeration value='unsubscribed'/>
               <xs:enumeration value='unavailable'/>
               <xs:enumeration value='error'/>
             </xs:restriction>
           </xs:simpleType>
         </xs:attribute>
       </xs:complexType>
     </xs:element>

     <xs:element name='show'>
       <xs:simpleType>
         <xs:restriction base='xs:NCName'>
           <xs:enumeration value='away'/>
           <xs:enumeration value='chat'/>
           <xs:enumeration value='dnd'/>
           <xs:enumeration value='xa'/>
         </xs:restriction>
       </xs:simpleType>
     </xs:element>

     <xs:element name='status' type='xs:string'>
       <xs:complexType>
         <xs:attribute ref='xml:lang' use='optional'/>
       </xs:complexType>
     </xs:element>

     <xs:element name='priority' type='xs:byte'/>

     <xs:element name='iq'>
       <xs:complexType>
         <xs:sequence>
           <xs:any     namespace='##other'
                       minOccurs='0'



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                       maxOccurs='1'/>
           <xs:element ref='error'
                       minOccurs='0'
                       maxOccurs='1'/>
         </xs:sequence>
         <xs:attribute name='to'
                       type='xs:string'
                       use='optional'/>
         <xs:attribute name='from'
                       type='xs:string'
                       use='optional'/>
         <xs:attribute name='id'
                       type='xs:NMTOKEN'
                       use='required'/>
         <xs:attribute ref='xml:lang' use='optional'/>
         <xs:attribute name='type' use='required'>
           <xs:simpleType>
             <xs:restriction base='xs:NCName'>
               <xs:enumeration value='get'/>
               <xs:enumeration value='set'/>
               <xs:enumeration value='result'/>
               <xs:enumeration value='error'/>
             </xs:restriction>
           </xs:simpleType>
         </xs:attribute>
       </xs:complexType>
     </xs:element>

     <xs:element name='error'>
       <xs:complexType>
         <xs:sequence>
           <xs:any namespace='urn:ietf:params:xml:ns:xmpp-stanzas'
                   maxOccurs='1'/>
           <text   namespace='urn:ietf:params:xml:ns:xmpp-stanzas'
                   minOccurs='0'
                   maxOccurs='1'/>
           <xs:any
               namespace='##other'
               minOccurs='0'
               maxOccurs='1'/>
         </xs:sequence>
         <xs:attribute name='type' use='required'/>
           <xs:simpleType>
             <xs:restriction base='xs:NCName'>
               <xs:enumeration value='cancel'/>
               <xs:enumeration value='continue'/>
               <xs:enumeration value='modify'/>
               <xs:enumeration value='auth'/>



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14. Differences Between Jabber and XMPP

   This section is non-normative.

   XMPP has been adapted from the protocols originally developed in the
   Jabber open-source community, which can be thought of as "XMPP 0.9".
   Because there exists a large installed base of Jabber implementations
   and deployments, it may be helpful to specify the key differences
   between Jabber and XMPP in order to expedite and encourage upgrades
   of those implementations and deployments to XMPP. This section
   summarizes the differences that relate specifically to instant
   messaging applications, and the corresponding section of XMPP Core
   [1] summarizes the differences that relate to all XMPP applications.

14.1 Session Creation

   The client-to-server authentication protocol developed in Jabber
   community assumes that the client is an IM client and therefore
   initiates an IM session upon successful authentication (documention
   of this protocol is contained in "JEP-0078: Non-SASL Authentication",
   published by the Jabber Software Foundation [5]). XMPP maintains a
   stricter separation between core functionality and IM functionality;
   therefore, an IM session is not created until the client specifically
   requests one using the protocol defined in the Establishing a Session
   (Section 2) section of this document.

14.2 Privacy Rules

   The Jabber community began to define a protocol for communications
   blocking (privacy rules) in late 2001, but that effort was deprecated
   once the XMPP Working Group was formed. Therefore the protocol
   defined in the Blocking Communication (Section 9) section of this
   document is the only such protocol defined for use in the Jabber
   community.


               <xs:enumeration value='wait'/>
             </xs:restriction>
           </xs:simpleType>
         </xs:attribute>
       </xs:complexType>
     </xs:element>

   </xs:schema>


B.2 jabber:server namespace

   <?xml version='1.0' encoding='UTF-8'?>

   <xs:schema
       xmlns:xs='http://www.w3.org/2001/XMLSchema'
       xmlns:xml='http://www.w3.org/XML/1998/namespace'
       targetNamespace='jabber:server'
       xmlns='jabber:server'
       elementFormDefault='qualified'>

     <xs:import namespace='http://www.w3.org/XML/1998/namespace'
                schemaLocation='http://www.w3.org/2001/xml.xsd'/>

     <xs:element name='message'>
        <xs:complexType>
           <xs:sequence>
              <xs:element ref='subject'
                          minOccurs='0'
                          maxOccurs='unbounded'/>
              <xs:element ref='body'
                          minOccurs='0'
                          maxOccurs='unbounded'/>
              <xs:element ref='thread'
                          minOccurs='0'
                          maxOccurs='1'/>
              <xs:any     namespace='##other'
                          minOccurs='0'
                          maxOccurs='unbounded'/>
              <xs:element ref='error'
                          minOccurs='0'
                          maxOccurs='1'/>
           </xs:sequence>
           <xs:attribute name='to'
                         type='xs:string'
                         use='required'/>
           <xs:attribute name='from'
                         type='xs:string'



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Normative References

   [1]  Saint-Andre, P. and J. Miller, "XMPP Core",
        draft-ietf-xmpp-core-17 (work in progress), August 2003.

   [2]  Day, M., Aggarwal, S. and J. Vincent, "Instant Messaging /
        Presence Protocol Requirements", RFC 2779, February 2000.

   [3]  Bradner, S., "Key words for use in RFCs to Indicate Requirement
        Levels", BCP 14, RFC 2119, March 1997.

   [4]  Saint-Andre, P., "End-to-End Object Encryption in XMPP",
        draft-ietf-xmpp-e2e-05 (work in progress), August 2003.


                         use='required'/>
           <xs:attribute name='id'
                         type='xs:NMTOKEN'
                         use='optional'/>
           <xs:attribute ref='xml:lang' use='optional'/>
           <xs:attribute name='type' use='optional'>
             <xs:simpleType>
               <xs:restriction base='xs:NCName'>
                 <xs:enumeration value='chat'/>
                 <xs:enumeration value='error'/>
                 <xs:enumeration value='groupchat'/>
                 <xs:enumeration value='headline'/>
                 <xs:enumeration value='normal'/>
               </xs:restriction>
             </xs:simpleType>
           </xs:attribute>
        </xs:complexType>
     </xs:element>

     <xs:element name='body' type='xs:string'>
       <xs:complexType>
         <xs:attribute ref='xml:lang' use='optional'/>
       </xs:complexType>
     </xs:element>

     <xs:element name='subject' type='xs:string'>
       <xs:complexType>
         <xs:attribute ref='xml:lang' use='optional'/>
       </xs:complexType>
     </xs:element>

     <xs:element name='thread' type='xs:NMTOKEN'/>

     <xs:element name='presence'>
       <xs:complexType>
         <xs:sequence>
           <xs:element ref='show'
                       minOccurs='0'
                       maxOccurs='1'/>
           <xs:element ref='status'
                       minOccurs='0'
                       maxOccurs='unbounded'/>
           <xs:element ref='priority'
                       minOccurs='0'
                       maxOccurs='1'/>
           <xs:any     namespace='##other'
                       minOccurs='0'
                       maxOccurs='unbounded'/>



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Informative References

   [5]  Jabber Software Foundation, "Jabber Software Foundation",
        <http://www.jabber.org/>.

   [6]  Day, M., Rosenberg, J. and H. Sugano, "A Model for Presence and
        Instant Messaging", RFC 2778, February 2000, <http://
        www.ietf.org/rfc/rfc2778.txt>.

   [7]  Dawson, F. and T. Howes, "vCard MIME Directory Profile", RFC
        2426,           September 1998.


Authors' Addresses

   Peter Saint-Andre
   Jabber Software Foundation

   EMail: stpeter@jabber.org


   Jeremie Miller
   Jabber Software Foundation

   EMail: jeremie@jabber.org 2003


           <xs:element ref='error'
                       minOccurs='0'
                       maxOccurs='1'/>
         </xs:sequence>
         <xs:attribute name='to'
                       type='xs:string'
                       use='required'/>
         <xs:attribute name='from'
                       type='xs:string'
                       use='required'/>
         <xs:attribute name='id'
                       type='xs:NMTOKEN'
                       use='optional'/>
         <xs:attribute ref='xml:lang' use='optional'/>
         <xs:attribute name='type' use='optional'>
           <xs:simpleType>
             <xs:restriction base='xs:NCName'>
               <xs:enumeration value='subscribe'/>
               <xs:enumeration value='subscribed'/>
               <xs:enumeration value='unsubscribe'/>
               <xs:enumeration value='unsubscribed'/>
               <xs:enumeration value='unavailable'/>
               <xs:enumeration value='error'/>
             </xs:restriction>
           </xs:simpleType>
         </xs:attribute>
       </xs:complexType>
     </xs:element>

     <xs:element name='show'>
       <xs:simpleType>
         <xs:restriction base='xs:NCName'>
           <xs:enumeration value='away'/>
           <xs:enumeration value='chat'/>
           <xs:enumeration value='dnd'/>
           <xs:enumeration value='xa'/>
         </xs:restriction>
       </xs:simpleType>
     </xs:element>

     <xs:element name='status' type='xs:string'>
       <xs:complexType>
         <xs:attribute ref='xml:lang' use='optional'/>
       </xs:complexType>
     </xs:element>

     <xs:element name='priority' type='xs:byte'/>




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Appendix A. vCards

   Sections 3.1.3 and 4.1.4 of RFC 2779 [2] require that it be possible
   to retrieve contact information for other users (e.g., telephone
   number or email address). An XML representation of the vCard
   specification defined in RFC 2426 [7] is in common use within the
   Jabber community to provide such information but is out of scope for
   XMPP (documentation of this protocol is contained in "JEP-0054:
   vcard-temp", published by the Jabber Software Foundation [5]).


     <xs:element name='iq'>
       <xs:complexType>
         <xs:sequence>
           <xs:any     namespace='##other'
                       minOccurs='0'
                       maxOccurs='1'/>
           <xs:element ref='error'
                       minOccurs='0'
                       maxOccurs='1'/>
         </xs:sequence>
         <xs:attribute name='to'
                       type='xs:string'
                       use='required'/>
         <xs:attribute name='from'
                       type='xs:string'
                       use='required'/>
         <xs:attribute name='id'
                       type='xs:NMTOKEN'
                       use='required'/>
         <xs:attribute ref='xml:lang' use='optional'/>
         <xs:attribute name='type' use='required'>
           <xs:simpleType>
             <xs:restriction base='xs:NCName'>
               <xs:enumeration value='get'/>
               <xs:enumeration value='set'/>
               <xs:enumeration value='result'/>
               <xs:enumeration value='error'/>
             </xs:restriction>
           </xs:simpleType>
         </xs:attribute>
       </xs:complexType>
     </xs:element>

     <xs:element name='error'>
       <xs:complexType>
         <xs:sequence>
           <xs:any namespace='urn:ietf:params:xml:ns:xmpp-stanzas'
                   maxOccurs='1'/>
           <text   namespace='urn:ietf:params:xml:ns:xmpp-stanzas'
                   minOccurs='0'
                   maxOccurs='1'/>
           <xs:any
               namespace='##other'
               minOccurs='0'
               maxOccurs='1'/>
         </xs:sequence>
         <xs:attribute name='type' use='required'/>
           <xs:simpleType>



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Appendix B. XML Schemas

   The following XML schemas are descriptive, not normative. For schemas
   defining the core features of XMPP, refer to XMPP Core [1].

B.1


             <xs:restriction base='xs:NCName'>
               <xs:enumeration value='cancel'/>
               <xs:enumeration value='continue'/>
               <xs:enumeration value='modify'/>
               <xs:enumeration value='auth'/>
               <xs:enumeration value='wait'/>
             </xs:restriction>
           </xs:simpleType>
         </xs:attribute>
       </xs:complexType>
     </xs:element>

   </xs:schema>


B.3 session

   <?xml version='1.0' encoding='UTF-8'?>
   <xs:schema
       xmlns:xs='http://www.w3.org/2001/XMLSchema'
       targetNamespace='urn:ietf:params:xml:ns:xmpp-session'
       xmlns='urn:ietf:params:xml:ns:xmpp-session'
       elementFormDefault='qualified'>

     <xs:element name='session' type='empty'/>

     <xs:simpleType name='empty'>
       <xs:restriction base='xs:string'>
         <xs:enumeration value=''/>
       </xs:restriction>
     </xs:simpleType>

   </xs:schema>


B.2 jabber:iq:last


B.4 jabber:iq:privacy

   <?xml version='1.0' encoding='UTF-8'?>
   <xs:schema
       xmlns:xs='http://www.w3.org/2001/XMLSchema'
       targetNamespace='jabber:iq:last'
       xmlns='jabber:iq:last'
       targetNamespace='jabber:iq:privacy'
       xmlns='jabber:iq:privacy'
       elementFormDefault='qualified'>

     <xs:element name='query'>
       <xs:complexType>
         <xs:attribute name='seconds'
                       type='xs:unsignedLong'
                       use='optional'/>
       </xs:complexType>
     </xs:element>

   </xs:schema>


B.3 jabber:iq:privacy

   <?xml version='1.0' encoding='UTF-8'?>
         <xs:sequence>
           <xs:element ref='active'



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   <xs:schema
       xmlns:xs='http://www.w3.org/2001/XMLSchema'
       targetNamespace='jabber:iq:privacy'
       xmlns='jabber:iq:privacy'
       elementFormDefault='qualified'>

     <xs:element name='query'>
       <xs:complexType>
         <xs:sequence>
           <xs:element ref='active'


                       minOccurs='0'
                       maxOccurs='1'/>
           <xs:element ref='default'
                       minOccurs='0'
                       maxOccurs='1'/>
           <xs:element ref='list'
                       minOccurs='0'
                       maxOccurs='unbounded'/>
         </xs:sequence>
       </xs:complexType>
     </xs:element>

     <xs:element name='active'>
       <xs:complexType>
         <xs:attribute name='name'
                       type='xs:string'
                       use='optional'/>
       </xs:complexType>
     </xs:element>

     <xs:element name='default'>
       <xs:complexType>
         <xs:attribute name='name'
                       type='xs:string'
                       use='optional'/>
       </xs:complexType>
     </xs:element>

     <xs:element name='list'>
       <xs:complexType>
         <xs:sequence>
           <xs:element ref='item'
                       minOccurs='0'
                       maxOccurs='unbounded'/>
         </xs:sequence>
         <xs:attribute name='name'
                       type='xs:string'
                       use='required'/>



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       </xs:complexType>
     </xs:element>

     <xs:element name='item'>
       <xs:complexType>
         <xs:sequence>
           <xs:element ref='iq'
                       minOccurs='0'
                       maxOccurs='1'/>
           <xs:element ref='message'



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                       minOccurs='0'
                       maxOccurs='1'/>
           <xs:element ref='presence-in'
                       minOccurs='0'
                       maxOccurs='1'/>
           <xs:element ref='presence-out'
                       minOccurs='0'
                       maxOccurs='1'/>
         </xs:sequence>
         <xs:attribute name='order'
                       type='xs:unsignedInt'
                       use='required'/>
         <xs:attribute name='value'
                       type='xs:string'
                       use='optional'/>
         <xs:attribute name='action' use='required'>
           <xs:simpleType>
             <xs:restriction base='xs:NCName'>
               <xs:enumeration value='allow'/>
               <xs:enumeration value='deny'/>
             </xs:restriction>
           </xs:simpleType>
         </xs:attribute>
         <xs:attribute name='type' use='optional'>
           <xs:simpleType>
             <xs:restriction base='xs:NCName'>
               <xs:enumeration value='group'/>
               <xs:enumeration value='jid'/>
               <xs:enumeration value='subscription'/>
             </xs:restriction>
           </xs:simpleType>
         </xs:attribute>
       </xs:complexType>
     </xs:element>

     <xs:element name='iq' type='empty'/>
     <xs:element name='message' type='empty'/>
     <xs:element name='presence-in' type='empty'/>



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     <xs:element name='presence-out' type='empty'/>

     <xs:simpleType name='empty'>
       <xs:restriction base='xs:string'>
         <xs:enumeration value=''/>
       </xs:restriction>
     </xs:simpleType>

   </xs:schema>


B.4




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B.5 jabber:iq:roster

   <?xml version='1.0' encoding='UTF-8'?>
   <xs:schema
       xmlns:xs='http://www.w3.org/2001/XMLSchema'
       targetNamespace='jabber:iq:roster'
       xmlns='jabber:iq:roster'
       elementFormDefault='qualified'>

     <xs:element name='query'>
       <xs:complexType>
         <xs:sequence>
           <xs:element ref='item'
                       minOccurs='0'
                       maxOccurs='unbounded'/>
         </xs:sequence>
       </xs:complexType>
     </xs:element>

     <xs:element name='item'>
       <xs:complexType>
         <xs:sequence>
           <xs:element ref='group'
                       minOccurs='0'
                       maxOccurs='unbounded'/>
         </xs:sequence>
         <xs:attribute name='jid' type='xs:string' use='required'/>
         <xs:attribute name='name' type='xs:string' use='optional'/>
         <xs:attribute name='subscription' use='optional'>
           <xs:simpleType>
             <xs:restriction base='xs:NCNAME'>
               <xs:enumeration value='to'/>
               <xs:enumeration value='from'/>
               <xs:enumeration value='both'/>
               <xs:enumeration value='none'/>
               <xs:enumeration value='remove'/>
             </xs:restriction>



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           </xs:simpleType>
         </xs:attribute>
         <xs:attribute name='ask' use='optional'>
           <xs:simpleType>
             <xs:restriction base='xs:NCNAME'>
               <xs:enumeration value='subscribe'/>
             </xs:restriction>
           </xs:simpleType>
         </xs:attribute>
       </xs:complexType>
     </xs:element>



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     <xs:element name='group' type='xs:string'/>

   </xs:schema>
















































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Appendix C. Differences Between Jabber and XMPP

   This section is non-normative.

   XMPP has been adapted from the protocols originally developed in the
   Jabber open-source community, which can be thought of as "XMPP 0.9".
   Because there exists a large installed base of Jabber implementations
   and deployments, it may be helpful to specify the key differences
   between Jabber and XMPP in order to expedite and encourage upgrades
   of those implementations and deployments to XMPP. This section
   summarizes the differences that relate specifically to instant
   messaging and presence applications, and the corresponding section of
   XMPP Core [1] summarizes the differences that relate to all XMPP
   applications.

C.1 Session Creation

   The client-to-server authentication protocol developed in the Jabber
   community assumes that every client is an IM client and therefore
   initiates an IM session upon successful authentication (documention
   of this protocol is contained in "JEP-0078: Non-SASL Authentication",
   published by the Jabber Software Foundation [7]). XMPP maintains a
   stricter separation between core functionality and IM functionality;
   therefore, an IM session is not created until the client specifically
   requests one using the protocol defined in the Establishing a Session
   (Section 3) section of this document.

C.2 Privacy Rules

   The Jabber community began to define a protocol for communications
   blocking (privacy rules) in late 2001, but that effort was deprecated
   once the XMPP Working Group was formed. Therefore the protocol
   defined in the Blocking Communication (Section 10) section of this
   document is the only such protocol defined for use in the Jabber
   community.
















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Appendix C. D. Revision History

   Note to RFC Editor: please remove this entire appendix, and the
   corresponding entries in the table of contents, prior to publication.

C.1

D.1 Changes from draft-ietf-xmpp-im-16

   o  Added sentence to make explicit that blocking all communication
      includes subscription-related presence stanzas.

   o  Added clause to make explicit that privacy rules must be applied
      before handling of subscription-related presence stanzas and
      corresponding generation of roster pushes.

   o  Added syntax and semantics section for the 'jabber:iq:roster'
      namespace.

   o  Removed content about 'jabber:iq:last' namespace.

   o  Added several internal references from the security considerations
      section to other sections of this document.

   o  Moved most delivery handling rules from XMPP IM to XMPP Core.

   o  Moved detailed stanza syntax descriptions from XMPP Core to XMPP
      IM.

   o  Moved stanza schemas from XMPP Core to XMPP IM.


D.2 Changes from draft-ietf-xmpp-im-15

   o  Specified stream error to be sent to active session if there is a
      conflict regarding session creation.

   o  Fixed several more typographical errors in the privacy rules
      examples.

   o  Corrected an error regarding server handling of IQ stanzas sent to
      bare JIDs.

   o  Added section on compliance requirements for instant messaging
      server and client implementations.

   o  Added non-normative section on differences between Jabber usage
      and XMPP specifications.


C.2





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D.3 Changes from draft-ietf-xmpp-im-14

   o  Added subscription state charts.

   o  Fixed several typographical errors in the privacy rules examples.

   o  Changed datatype of 'order' attribute in privacy rules from
      nonNegativeInteger to unsignedInt.


C.3


D.4 Changes from draft-ietf-xmpp-im-13

   o  Made one small change to privacy list syntax rules.


C.4


D.5 Changes from draft-ietf-xmpp-im-12

   o  Clarified meaning of the default message type as well as handling
      of unknown or unsupported types.

   o  Made several small editorial changes.







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C.5


D.6 Changes from draft-ietf-xmpp-im-11

   o  Further clarified subscription syntax and semantics.

   o  Further clarified presence responsibilities for clients and
      servers.

   o  Added 'xml:lang' example to presence status.

   o  Added subsection on presence priority.

   o  Defined server handling of unsolicited presence stanzas of type
      "subscribed".

   o  Specified default resource priority if not provided.

   o  Corrected several errors in the schemas.

   o  Added privacy list business rule regarding roster changes.

   o  Removed the 'jabber:iq:privacy:error' namespace (not necessary).

   o  Documented message type='normal'.

   o  Made numerous small editorial changes throughout.


C.6



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D.7 Changes from draft-ietf-xmpp-im-10

   o  Clarified presence responsibilities for servers and clients.

   o  Clarified the routing and delivery rules for servers.

   o  Made the 'xml:lang' examples more complete.

   o  Corrected several errors in the unsubscribe workflow.

   o  Made small editorial changes in several sections.


C.7


D.8 Changes from draft-ietf-xmpp-im-09

   o  Clarified rules regarding allowable JID types in rosters.

   o  Further clarified the semantics and routing implications of
      presence priorities.

   o  Removed several obsolete subsections.



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C.8


D.9 Changes from draft-ietf-xmpp-im-08

   o  Removed authorization content (now addressed in XMPP Core).

   o  Added protocol for initiating an IM session, including schema and
      IANA registration template.

   o  Corrected <*-condition/> elements to be <condition/>.

   o  Made small editorial changes to address RFC Editor requirements.


C.9


D.10 Changes from draft-ietf-xmpp-im-07

   o  Added several error cases for resource authorization and updated
      relevant schema.


C.10


D.11 Changes from draft-ietf-xmpp-im-06

   o  Specified that IQ result stanzas are required in response to
      roster pushes.

   o  Changed stanza error namespace names to conform to the format
      defined in "The IETF XML Registry" as specified in XMPP Core.



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   o  Removed note to RFC Editor regarding provisional namespace names.


C.11


D.12 Changes from draft-ietf-xmpp-im-05

   o  Removed use of ask='unsubscribe' per list discussion.

   o  Clarified handling of resource conflict during authorization.

   o  Added schemas for jabber:iq:auth, jabber:iq:auth:error, and
      jabber:iq:privacy:error.

   o  Corrected several small protocol errors in the examples.

   o  Clarified semantics of message types.


C.12


D.13 Changes from draft-ietf-xmpp-im-04

   o  Specified sending of unavailable presence after unsubscribe and
      subscription-cancellation actions.




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   o  Further specified syntax and business rules for privacy lists.

   o  Brought error codes into line with definitions in
      draft-ietf-xmpp-core.

   o  Added note to RFC Editor regarding provisional namespace names.

   o  Removed vCard content and DTD, instead pointing to JSF
      documentation.


C.13


D.14 Changes from draft-ietf-xmpp-im-03

   o  Fixed order processing on privacy rules per list discussion.

   o  Made numerous small editorial changes.


C.14


D.15 Changes from draft-ietf-xmpp-im-02

   o  Added a great deal more detail to the narrative regarding
      server-side privacy rules as well as the interaction between
      rosters and subscriptions.

   o  Removed DTDs in favor of schemas (with the exception of vCard
      XML).



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   o  Removed non-normative documentation of authentication using
      jabber:iq:auth and of in-band registration using
      jabber:iq:register, since these are maintained by the Jabber
      Software Foundation and are not part of the XMPP specification.


C.15


D.16 Changes from draft-ietf-xmpp-im-01

   o  Made numerous small editorial changes.


C.16


D.17 Changes from draft-ietf-xmpp-im-00

   o  Moved registration and authentication via jabber:iq:auth to
      non-normative appendices.

   o  Changed initial presence stanza from MUST be empty to SHOULD be
      empty.

   o  Specified that user or clients should not send presence stanzas of
      type='probe'.



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   o  Specified the algorithm for digest passwords.


C.17


D.18 Changes from draft-miller-xmpp-im-02

   o  Added information about the 'jabber:iq:last' protocol to meet the
      requirement defined in section 3.2.4 of RFC 2779.

   o  Added information about the 'jabber:iq:privacy' protocol to meet
      the requirement defined in section 2.3.5 of RFC 2779.

   o  Added information about the vCard XML protocol to meet the
      requirement defined in sections 3.1.3 and 4.1.4 of RFC 2779.

   o  Changed the material describing authentication (but not resource
      authorization) with 'jabber:iq:auth' to non-normative.

   o  Noted that the only watchers are subscribers.

   o  Nomenclature changes: (1) from "chunks" to "stanzas"; (2) from
      "host" to "server"; (3) from "node" to "client" or "user" (as
      appropriate).







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   HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF
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Acknowledgment

   Funding for the RFC Editor function is currently provided by the
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----