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Network Working Group                                     P. Saint-Andre
Internet-Draft                                                 J. Miller
Expires: December 28, 2003 January 26, 2004                     Jabber Software Foundation
                                                           June 29,
                                                           July 28, 2003


                         XMPP Instant Messaging
                         draft-ietf-xmpp-im-14
                         draft-ietf-xmpp-im-15

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 December 28, 2003. January 26, 2004.

Copyright Notice

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

Abstract

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











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Table of Contents

   1.    Introduction . . . . . . . . . . . . . . . . . . . . . . . .  4    5
   1.1   Overview . . . . . . . . . . . . . . . . . . . . . . . . . .  4    5
   1.2   Requirements . . . . . . . . . . . . . . . . . . . . . . . .  4    5
   1.3   Terminology  . . . . . . . . . . . . . . . . . . . . . . . .  4    5
   1.4   Discussion Venue . . . . . . . . . . . . . . . . . . . . . .  5    6
   1.5   Intellectual Property Notice . . . . . . . . . . . . . . . .  5    6
   2.    Establishing a Session . . . . . . . . . . . . . . . . . . .  6    7
   3.    Exchanging Messages  . . . . . . . . . . . . . . . . . . . .  8    9
   3.1   Specifying an Intended Recipient . . . . . . . . . . . . . .  8    9
   3.2   Specifying a Message Type  . . . . . . . . . . . . . . . . .  8    9
   3.3   Specifying a Message Body  . . . . . . . . . . . . . . . . .  9   10
   3.4   Specifying a Message Subject . . . . . . . . . . . . . . . . 10   11
   3.5   Specifying a Conversation Thread . . . . . . . . . . . . . . 10   11
   4.    Exchanging Presence Information  . . . . . . . . . . . . . . 12   13
   4.1   Client and Server Responsibilities . . . . . . . . . . . . . 12   13
   4.2   Specifying Availability Status . . . . . . . . . . . . . . . 14   16
   4.3   Specifying Detailed Status Information . . . . . . . . . . . 15   16
   4.4   Specifying Presence Priority . . . . . . . . . . . . . . . . 15   16
   4.5   Determining When a Contact Went Offline  . . . . . . . . . . 16   17
   4.6   Presence Examples  . . . . . . . . . . . . . . . . . . . . . 17   18
   5.    Managing Subscriptions . . . . . . . . . . . . . . . . . . . 22   23
   5.1   Requesting a Subscription  . . . . . . . . . . . . . . . . . 22   23
   5.2   Handling a Subscription Request  . . . . . . . . . . . . . . 22   23
   5.3   Cancelling a Subscription from Another Entity  . . . . . . . 23   24
   5.4   Unsubscribing from Another Entity's Presence . . . . . . . . 23   24
   6.    Managing One's Roster  . . . . . . . . . . . . . . . . . . . 24   25
   6.1   Retrieving One's Roster on Login . . . . . . . . . . . . . . 24   25
   6.2   Adding a Roster Item . . . . . . . . . . . . . . . . . . . . 25   26
   6.3   Updating a Roster Item . . . . . . . . . . . . . . . . . . . 26   27
   6.4   Deleting a Roster Item . . . . . . . . . . . . . . . . . . . 27   28
   7.    Integration of Roster Items and Presence Subscriptions . . . 28   29
   7.1   Overview . . . . . . . . . . . . . . . . . . . . . . . . . . 28   29
   7.2   User Subscribes to Contact . . . . . . . . . . . . . . . . . 28   29
   7.2.1 Alternate Flow: Contact Declines Subscription Request  . . . 32   34
   7.3   Creating a Mutual Subscription . . . . . . . . . . . . . . . 33   35
   7.3.1 Alternate Flow: User Declines Subscription Request . . . . . 36   38
   7.4   Unsubscribing  . . . . . . . . . . . . . . . . . . . . . . . 37   40
   7.4.1 Case #1: Unsubscribing When Subscription is Not Mutual . . . 38   40
   7.4.2 Case #2: Unsubscribing When Subscription is Mutual . . . . . 39   42
   7.5   Cancelling a Subscription  . . . . . . . . . . . . . . . . . 42   45
   7.5.1 Case #1: Cancelling When Subscription is Not Mutual  . . . . 42   45
   7.5.2 Case #2: Cancelling When Subscription is Mutual  . . . . . . 44   47
   7.6   Removing a Roster Item and Cancelling All Subscriptions  . . 46   49
   8.    Blocking Communication    Subscription States  . . . . . . . . . . . . . . . . . . . 49   53
   8.1   Syntax   Defined States . . . . . . . . . . . . . . . . . . . . . .   53
   8.2   Server Handling of Outbound Presence, Categorized by



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         Subscription State . . . . . . 49
   8.2   Business Rules . . . . . . . . . . . . . .   53
   8.2.1 Subscription State = None  . . . . . . . . . 51



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   8.3   Retrieving One's Privacy Lists . . . . . . .   54
   8.2.2 Subscription State = None + Pending Out  . . . . . . . . 52
   8.4   Managing Active Lists .   54
   8.2.3 Subscription State = None + Pending In . . . . . . . . . .   54
   8.2.4 Subscription State = None + Pending Out/In . . . . . . . .   55
   8.5   Managing the Default List
   8.2.5 Subscription State = To  . . . . . . . . . . . . . . . . . 56
   8.6   Editing a Privacy List   55
   8.2.6 Subscription State = To + Pending In . . . . . . . . . . .   55
   8.2.7 Subscription State = From  . . . . . . . . 57
   8.7   Adding a New Privacy List . . . . . . . .   56
   8.2.8 Subscription State = From + Pending Out  . . . . . . . . . 58
   8.8   Removing a Privacy List   56
   8.2.9 Subscription State = Both  . . . . . . . . . . . . . . . .   56
   8.3   Server Handling of Outbound Presence, Categorized by
         Presence Type  . . 58
   8.9   Blocking Messages . . . . . . . . . . . . . . . . . . . .   56
   8.3.1 Subscribe  . 59
   8.10  Blocking Inbound Presence Notifications . . . . . . . . . . 60
   8.11  Blocking Outbound Presence Notifications . . . . . . . . . . 62
   8.12  Blocking IQs . . .   57
   8.3.2 Subscribed . . . . . . . . . . . . . . . . . . . . . 64
   8.13  Blocking All Communication . . .   57
   8.3.3 Unsubscribe  . . . . . . . . . . . . . . 65
   8.14  Blocked Entity Attempts to Communicate with User . . . . . . 67
   8.15  Higher-Level Heuristics . . .   58
   8.3.4 Unsubscribed . . . . . . . . . . . . . . . 68
   9.    Server Rules for Handling XML Stanzas . . . . . . . .   58
   8.4   Server Handling of Inbound Presence, Categorized by
         Subscription State . . . 70
   9.1   No 'to' Address . . . . . . . . . . . . . . . . .   58
   8.4.1 Subscription State = None  . . . . . 70
   9.2   Foreign Domain . . . . . . . . . . .   59
   8.4.2 Subscription State = None + Pending Out  . . . . . . . . .   59
   8.4.3 Subscription State = None + Pending In . . . 70
   9.3   Subdomain . . . . . . .   59
   8.4.4 Subscription State = None + Pending Out/In . . . . . . . .   60
   8.4.5 Subscription State = To  . . . . . . . . . . 70
   9.4   Bare Domain or Specific Resource . . . . . . .   60
   8.4.6 Subscription State = To + Pending In . . . . . . . 70
   9.5   User in Same Domain . . . .   60
   8.4.7 Subscription State = From  . . . . . . . . . . . . . . . . 71
   10.   IANA Considerations   61
   8.4.8 Subscription State = From + Pending Out  . . . . . . . . .   61
   8.4.9 Subscription State = Both  . . . . . . . . . . . 73
   10.1  XML Namespace Name for Session Data . . . . .   61
   8.5   Server Handling of Inbound Presence, Categorized by
         Presence Type  . . . . . . . 73
   11.   Security Considerations . . . . . . . . . . . . . . .   61
   8.5.1 Subscribe  . . . 74
         Normative References . . . . . . . . . . . . . . . . . . . . 75
         Informative References .   62
   8.5.2 Subscribed . . . . . . . . . . . . . . . . . . 76
         Authors' Addresses . . . . . .   62
   8.5.3 Unsubscribe  . . . . . . . . . . . . . . . 76
   A.    vCards . . . . . . . .   63
   8.5.4 Unsubscribed . . . . . . . . . . . . . . . . . . . 77
   B.    XML Schemas . . . .   63
   8.6   Server Delivery and Client Acknowledgement of
         Subscription State Change Notifications  . . . . . . . . .   63
   9.    Blocking Communication . . . . . . . . . . . 78
   B.1   session . . . . . . .   65
   9.1   Syntax . . . . . . . . . . . . . . . . . . . 78
   B.2   jabber:iq:last . . . . . . .   65
   9.2   Business Rules . . . . . . . . . . . . . . . . 78
   B.3   jabber:iq:privacy . . . . . .   67
   9.3   Retrieving One's Privacy Lists . . . . . . . . . . . . . .   68
   9.4   Managing Active Lists  . 78
   B.4   jabber:iq:roster . . . . . . . . . . . . . . . . .   71
   9.5   Managing the Default List  . . . . . 81
   C.    Revision History . . . . . . . . . . .   72
   9.6   Editing a Privacy List . . . . . . . . . . . 83
   C.1   Changes from draft-ietf-xmpp-im-13 . . . . . . .   73
   9.7   Adding a New Privacy List  . . . . . . 83
   C.2   Changes from draft-ietf-xmpp-im-12 . . . . . . . . . .   74
   9.8   Removing a Privacy List  . . . 83
   C.3   Changes from draft-ietf-xmpp-im-11 . . . . . . . . . . . . . 83
   C.4   Changes from draft-ietf-xmpp-im-10 .   74
   9.9   Blocking Messages  . . . . . . . . . . . . 83
   C.5   Changes from draft-ietf-xmpp-im-09 . . . . . . . .   75
   9.10  Blocking Inbound Presence Notifications  . . . . . 84
   C.6   Changes from draft-ietf-xmpp-im-08 . . . .   76
   9.11  Blocking Outbound Presence Notifications . . . . . . . . . 84
   C.7   Changes from draft-ietf-xmpp-im-07   78
   9.12  Blocking IQs . . . . . . . . . . . . . 84
   C.8   Changes from draft-ietf-xmpp-im-06 . . . . . . . . . .   80



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   9.13  Blocking All Communication . . . 84
   C.9   Changes from draft-ietf-xmpp-im-05 . . . . . . . . . . . . . 85
   C.10  Changes from draft-ietf-xmpp-im-04   81
   9.14  Blocked Entity Attempts to Communicate with User . . . . .   83
   9.15  Higher-Level Heuristics  . . . . . . . . 85
   C.11  Changes from draft-ietf-xmpp-im-03 . . . . . . . . .   84
   10.   Server Rules for Handling XML Stanzas  . . . . 85
   C.12  Changes from draft-ietf-xmpp-im-02 . . . . . .   86
   10.1  No 'to' Address  . . . . . . . . 85
   C.13  Changes from draft-ietf-xmpp-im-01 . . . . . . . . . . . . .   86
   C.14  Changes from draft-ietf-xmpp-im-00
   10.2  Foreign Domain . . . . . . . . . . . . . . . . . . . . . .   86
   C.15  Changes from draft-miller-xmpp-im-02
   10.3  Subdomain  . . . . . . . . . . . . . . . . . . . . . . . .   86
         Intellectual Property and Copyright Statements
   10.4  Bare Domain or Specific Resource . . . . . . . 87



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1. Introduction

1.1 Overview

   The core features of the Extensible Messaging and Presence Protocol
   are defined . . . . . .   86
   10.5  User in XMPP Core [1]. These features -- specifically Same Domain  . . . . . . . . . . . . . . . . . . .   87
   11.   IANA Considerations  . . . . . . . . . . . . . . . . . . .   89
   11.1  XML
   streams, stream authentication and encryption, and the <message/>,
   <presence/>, and <iq/> children of the stream root -- provide the
   building blocks Namespace Name 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. 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 Session Data  . . . . . . . . . . .   89
   12.   Security Considerations  . . . . . . . . . . . . . . . . .   90
         Normative References . . . . . . . . . . . . . . . . . . .   91
         Informative References . . . . . . . . . . . . . . . . . .   92
         Authors' Addresses . . . . . . . . . . . . . . . . . . . .   92
   A.    vCards . . . . . . . . . . . . . . . . . . . . . . . . . .   93
   B.    XML Schemas  . . . . . . . . . . . . . . . . . . . . . . .   94
   B.1   session  . . . . . . . . . . . . . . . . . . . . . . . . .   94
   B.2   jabber:iq:last . . . . . . . . . . . . . . . . . . . . . .   94
   B.3   jabber:iq:privacy  . . . . . . . . . . . . . . . . . . . .   94
   B.4   jabber:iq:roster . . . . . . . . . . . . . . . . . . . . .   97
   C.    Revision History . . . . . . . . . . . . . . . . . . . . .   99
   C.1   Changes from draft-ietf-xmpp-im-14 . . . . . . . . . . . .   99
   C.2   Changes from draft-ietf-xmpp-im-13 . . . . . . . . . . . .   99
   C.3   Changes from draft-ietf-xmpp-im-12 . . . . . . . . . . . .   99
   C.4   Changes from draft-ietf-xmpp-im-11 . . . . . . . . . . . .   99
   C.5   Changes from draft-ietf-xmpp-im-10 . . . . . . . . . . . .  100
   C.6   Changes from draft-ietf-xmpp-im-09 . . . . . . . . . . . .  100
   C.7   Changes from draft-ietf-xmpp-im-08 . . . . . . . . . . . .  100
   C.8   Changes from draft-ietf-xmpp-im-07 . . . . . . . . . . . .  100
   C.9   Changes from draft-ietf-xmpp-im-06 . . . . . . . . . . . .  101
   C.10  Changes from draft-ietf-xmpp-im-05 . . . . . . . . . . . .  101
   C.11  Changes from draft-ietf-xmpp-im-04 . . . . . . . . . . . .  101
   C.12  Changes from draft-ietf-xmpp-im-03 . . . . . . . . . . . .  101
   C.13  Changes from draft-ietf-xmpp-im-02 . . . . . . . . . . . .  102
   C.14  Changes from draft-ietf-xmpp-im-01 . . . . . . . . . . . .  102
   C.15  Changes from draft-ietf-xmpp-im-00 . . . . . . . . . . . .  102
   C.16  Changes from draft-miller-xmpp-im-02 . . . . . . . . . . .  102
         Intellectual Property and Copyright Statements . . . . . .  104












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1. Introduction

1.1 Overview

   The core features of the Extensible Messaging and Presence Protocol
   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. 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].

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].

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 instant messaging and presence applications based on XMPP are
   implemented via a client-server architecture that requires a user to
   establish a session on a server in order to engage in the expected
   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 the 'jabber:iq:register' namespace;
       the latter method is documented by the Jabber Software Foundation
       [4] 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 include an
       authorization identity that specifies the full JID
       (<user@somedomain/resource>) associated with the connection for
       addressing purposes.

   Once a client has authenticated with a server and has authorized a
   full JID, it SHOULD request that the server activate an instant
   messaging session for the client. This is accomplished 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 error conditions are possible. For example, the server may
   encounter an internal condition that prevents it from creating the
   session, the username or authorization identity may lack permissions
   to create a session, or there may already be an active session
   associated with an authzid of the same name.

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





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   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 username or authorization identity is not allowed to create a
   session, the server MUST return an error.

   Step 2 (alt): Server responds with error (username or 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 already an 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 (2) disallow the
   newly-requested session and maintain the existing session. Which of
   these the server does is up to the implementation, although it is
   RECOMMENDED to implement (1).

   Step 2 (alt): Server informs client of resource conflict (the desired
   resource name is already in use by another active connection):

   <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'/>
     </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 a basic use of XMPP and is effected when a
   user generates a message stanza that is addressed to another user
   (or, more generally, another entity). As defined under Section 10,
   the sender's server is responsible for delivering the message to the
   intended recipient (if the recipient is on the same server) or for
   routing the message to the recipient's server (if the recipient is on
   a different server).

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

3.1 Specifying an Intended Recipient

   An instant messaging client SHOULD specify an intended recipient for
   a message by providing the JID of an entity other than the sender in
   the 'to' attribute of the <message/> stanza. If the message is being
   sent in reply to a message previously received from an address of the
   form <user@somedomain/resource> (e.g., within the context of a chat
   session), the value of the 'to' address SHOULD be the full JID
   (<user@somedomain/resource>) rather than merely <user@somedomain>
   unless the sender has knowledge (via presence) that the intended
   recipient's resource is no longer available. If the message is being
   sent outside the context of any existing chat session or received
   message, the value of the 'to' address SHOULD be of the form
   <user@somedomain> rather than <user@somedomain/resource>.

3.2 Specifying a Message Type

   As mentioned in XMPP Core [1], there are several 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 of the message, thus providing a
   hint regarding presentation (e.g., in a GUI). If the 'type' attribute
   is included, it SHOULD have one of the 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 SHOULD present an interface
      enabling one-to-one chat between the two parties, including an
      appropriate conversation history.

   o  error -- An error has occurred related to a previous message sent
      by the sender (for details regarding stanza error syntax, refer to
      XMPP Core [1]). A compliant client SHOULD present an appropriate
      interface informing the sender of the nature of the error.



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   o  groupchat -- The message is sent in 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
      of parties in the chatroom 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 to the message is
      expected, and a compliant client SHOULD present an interface that
      appropriately differentiates the message from standalone messages,
      chat sessions, or groupchat sessions (e.g., by not providing the
      recipient with the ability to reply).

   o  normal -- The message is a standalone message to which the
      recipient MAY reply if desired. This is the default type.

   An IM application SHOULD support all of the foregoing message types;
   if an application receives a basic
   instant messaging and presence message with no 'type' attribute or the
   application are defined by RFC 2779
   [2]. At does not understand the value of the 'type' attribute
   provided, it MUST consider the message to be of type "normal".

   Although the 'type' attribute is NOT REQUIRED, it is considered
   polite to mirror the type in any replies to a high level, RFC 2779 stipulates that message; furthermore,
   some specialized applications (e.g., a user must 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 able included to
   complete provide
   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 primary meaning in different languages, as long as each such
   element possesses an 'xml:lang' attribute with a contact list (in distinct value.












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   Example: A message with a "roster")

   o  Block communications to 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>
   </message>


3.4 Specifying a Message Subject

   A message stanza MAY contain one or from specific other users

   Detailed definitions more child <subject/> elements
   specifying the topic of these functionality areas are contained in
   RFC 2779, and the interested reader is directed to that document
   regarding message. The content of the requirements addressed herein.

   Note: while XMPP-based instant messaging subject
   element MUST be XML character data and presence meets the
   requirements of RFC 2779, it was not designed explicitly element MUST NOT contain
   mixed content. Multiple <subject/> elements MAY be included, as long
   as each such element possesses an 'xml:lang' attribute with RFC
   2779 a
   distinct value.

   Example: 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 a Conversation Thread

   A message stanza MAY contain a child <thread/> element specifying the
   conversation thread in mind, since which the base protocol evolved through an open
   development process within message is situated, for the Jabber open-source community before
   RFC 2779 was written. Note also purpose
   of tracking the conversation. The content of the <thread/> element is
   a random string that although protocols addressing
   many other functionality areas have been defined in is generated by the Jabber
   community, such protocols are not included sender in this document because
   they are not required by RFC 2779 [2].

1.3 Terminology

   This document inherits accordance with
   the terminology defined algorithm specified in XMPP Core [1]. [1]; this string SHOULD be
   copied back to the sender in subsequent replies.






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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].

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


   Example: A threaded conversation:

   <message
       to='romeo@example.net/orchard'
       from='juliet@example.com/balcony'
       type='chat'>
     <body>Art thou not Romeo, 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, Montague?</body>
     <thread>e0ffe42b28561960c6b12b944a092794b9683a38</thread>
   </message>

   <message
       to='juliet@example.com/balcony'
       from='romeo@example.net/orchard'
       type='chat'>
     <body>Neither, fair saint, if any. 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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2. Establishing a Session

   Most instant messaging and


4. Exchanging Presence Information

   Exchanging presence applications based on information is made relatively straightforward
   within XMPP are
   implemented via a client-server architecture that requires by using presence stanzas. However, we see here a user
   contrast to
   establish a session on the handling of messages: although a server in order client MAY send
   directed presence information to engage in the expected
   instant messaging and another entity, normally presence activities. However, there are several
   pre-conditions that must be met before a user may establish such
   information is sent from a
   session. These include:

   1.  Account Provisioning -- methods for account provisioning include
       account creation client to its server (with no 'to'
   address) and then broadcasted by a the server administrator as well as in-band
       account registration using to any entities that are
   subscribed to the 'jabber:iq:register' namespace; presence of the latter method is documented by sending entity. (Note: in the Jabber Software Foundation
       [4] at <http://www.jabber.org/protocol/> but is out
   terminology of scope for
       this document.

   2.  Authentication and Resource Authorization -- methods for
       completing these pre-conditions are documented RFC 2778 [5], the only watchers in XMPP Core [1];
       note that client authentication with a server MUST include an
       authorization identity that specifies the full JID (<user@domain/
       resource>) associated with are
   subscribers.)

   For information regarding the connection for addressing
       purposes.

   Once a client has authenticated with a server syntax of presence stanzas as well as
   their defined attributes and has authorized child elements, refer to XMPP Core [1].

4.1 Client and Server Responsibilities

   When a
   full JID, client connects to its server, it SHOULD request that (but is NOT REQUIRED
   to) send initial presence to the server activate an instant
   messaging session in order to signal its
   availability for communications. As defined herein, the client. This initial
   presence stanza (1) MUST possess no 'to' address (signalling that it
   is accomplished meant to be handled by means the server on behalf 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 error conditions are possible. For example, user) and (2)
   MUST possess no 'type' attribute (signalling the server may
   encounter an internal condition that prevents it user's
   availability).

   Upon receiving initial presence from creating a client, the
   session, user's server MUST
   do the username or authorization identity may lack permissions following:

   1.  Send presence probes (i.e., presence stanzas whose 'type'
       attribute is set to create a session, or there may already be an active session
   associated with an authzid value of "probe") from the same name.

   If full JID
       (<user@somedomain/resource>) of the server encounters an internal condition that prevents it from
   creating user to the session, it MUST return an error.





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   Step 2 (alt): Server responds bare JID
       (<contact@otherdomain>) of any contacts to which the user is
       subscribed in order to determine if they are available; such
       contacts are those which are present in the user's roster 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 username or authorization identity is not allowed 'subscription' attribute set to a value of "to" or "both".
       (Note: a user or client SHOULD NOT send presence probes.)

   2.  Broadcast initial presence from the full JID (<user@somedomain/
       resource>) of the user to create a
   session, the server MUST return an error.

   Step 2 (alt): Server responds with error (username or authzid not
   allowed bare JID (<contact@otherdomain>) of
       any contacts that are subscribed 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 the user's presence; such
       contacts are those which are present in the user's roster with an authzid
       the 'subscription' attribute set to a value of "from" or "both".

   Upon receiving a presence probe from the same name, user, the contact's server
   MUST either (1) terminate send to the active
   session and allow user the newly-requested session, or (2) disallow last known availability information (i.e.,
   the
   newly-requested session and maintain full XML of the existing session. Which last presence stanza) provided by each of
   these the
   contact's active sessions (if there exist no active sessions, the
   server does is up SHOULD NOT reply to the implementation, although it is
   RECOMMENDED to implement (1).

   Step 2 (alt): Server informs client of resource conflict (the desired
   resource name is already in use by another active connection):

   <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'/>
     </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. probe). The server MUST send



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3. Exchanging Messages

   Exchanging messages


   this information subject to domain-specific access rules, and only if
   the user is in the contact's roster with a basic use subscription state of XMPP
   "from" or "both" and is effected when the contact has not blocked outbound presence
   notifications to the user's bare or full JID (as defined in Section
   9.11). (Note: if the server receives a
   user generates presence probe from a message stanza that is addressed to
   subdomain of the server's hostname or another such trusted service,
   it MAY provide presence information about the user
   (or, more generally, another entity). As defined under Section 9, to that entity.)

   Upon receiving initial presence from the
   sender's user, the contact's server is responsible for delivering
   MUST deliver the message user's presence stanza to the
   intended recipient (if full JIDs
   (<contact@otherdomain/resource>) associated with all of the recipient contact's
   active sessions, but only if the user is on in the same server) contact's roster with
   a subscription state of "to" or for
   routing "both" and the message to contact has not
   blocked inbound presence notifications from the recipient's user's bare or full
   JID (as defined in Section 9.10).

   If the user's server (if receives a presence stanza of type "error" in
   response to the recipient is initial presence that it forwarded to a contact on
   behalf of the user, it SHOULD NOT send further presence updates to
   that contact (until and unless it receives a different server).

   For information regarding presence probe from the syntax of message stanzas as well as
   their defined attributes
   contact).

   After sending initial presence, the user MAY update and child elements, refer to XMPP Core [1].

3.1 Specifying an Intended Recipient

   An instant messaging broadcast its
   presence information at any time during its active session by sending
   a 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 specify an intended recipient for NOT send a message by providing the JID presence update to broadcast information
   that changes independently of an entity other than the sender in user's presence and availability.)
   If the 'to' presence stanza lacks a 'type' attribute of (i.e., expresses
   availability), the <message/> stanza. If user's server MUST broadcast the message is being
   sent in reply full XML of that
   presence stanza to all contacts (1) that are in the user's roster
   with a message previously received from an address subscription type of "from" or "both", (2) to whom the
   form <user@domain/resource> (e.g., within user
   has not blocked outbound presence, and (3) from whom the context of server has
   not received a chat
   session), presence error during the user's session. If the
   presence stanza has a 'type' attribute set to a value of
   "unavailable", the 'to' address SHOULD be user's server MUST broadcast the full JID
   (<user@domain/resource>) rather than merely <user@domain> unless the
   sender has knowledge (via presence) XML of that
   presence stanza to all contacts meeting the intended recipient's
   resource is no longer available. If three conditions just
   mentioned, as well as to any entities to which the message is being user has sent outside
   directed available presence during the context of any existing chat user's session or received message, the
   value of the 'to' address SHOULD be of (if the form <user@domain> rather
   than <user@domain/resource>.

3.2 Specifying user
   has not yet sent directed unavailable presence to that entity).

   A user MAY send directed presence to another entity (i.e., a Message Type

   As mentioned in XMPP Core [1], there are several defined types of
   messages (specified by means presence
   stanza with a 'to' attribute whose value is the JID of the other
   entity and with either no 'type' attribute or a 'type' attribute within the
   <message/> element). In
   whose value is "unavailable"). There are three possible cases:

   1.  If the context of an instant messaging
   application, user sends directed presence to a client SHOULD include contact that is in the
       user's roster with a message subscription type in order to
   capture of "from" or "both" after



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       having sent initial presence and before sending unavailable
       presence broadcast, the conversational context user's server MUST route or deliver the
       full XML of that presence stanza (subject to privacy rules) but
       SHOULD NOT otherwise modify the message, thus providing a
   hint contact's status regarding presentation (e.g., in a GUI). If the 'type' attribute
   is included,
       presence broadcast (i.e., it SHOULD have one of include the following values (any other
   value MAY be ignored):

   o  chat -- The message is sent contact's JID in
       any subsequent presence broadcasts initiated by the context of a one-to-one chat
      conversation. A compliant client SHOULD present an interface
      enabling one-to-one chat between user).

   2.  If the two parties, including an
      appropriate conversation history.

   o  error -- An error has occurred related user sends directed presence to an entity that is not in
       the user's roster with a previous message subscription type of "from" or "both"
       after having sent
      by initial presence and before sending unavailable
       presence broadcast, the sender (for details regarding stanza error syntax, refer to
      XMPP Core [1]). A compliant client SHOULD present an appropriate
      interface informing user's server MUST route or deliver the
       full XML of that presence stanza to the sender of entity but MUST NOT
       modify the nature of contact's status regarding available presence
       broadcast (i.e., it MUST NOT include the error.



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   o  groupchat -- The message is sent entity's JID in the context any
       subsequent broadcasts of a multi-user
      chat environment. A compliant client SHOULD present an interface
      enabling many-to-many chat between available presence initiated by the parties, including a roster
      of parties in
       user); however, if the chatroom and an appropriate conversation
      history.

   o  headline -- The message is probably generated by an automated
      service connected resource from which the user
       sent the directed presence become unavailable, the user's server
       MUST broadcast that delivers or broadcasts content (news, sports, market
      information, RSS feeds, etc.). No reply unavailable presence to the message is
      expected, and a compliant client SHOULD present an interface entity (if the
       user has not yet sent directed unavailable presence to that
      appropriately differentiates
       entity).

   3.  If the message from standalone messages,
      chat sessions, user sends directed presence without first sending initial
       presence or groupchat sessions (e.g., by not providing after having sent unavailable presence broadcast, the
      recipient with
       user's server MUST treat the ability to reply).

   o  normal -- The message is a standalone message entities to which the
      recipient MAY reply if desired. This is user sends
       directed presence in the default type.

   An IM application SHOULD support all of same way that it treats the foregoing message types;
   if an application receives entities
       listed in Case 2 above.

   Before ending its session with a server, a client SHOULD gracefully
   become unavailable by sending a message with 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 the
   application does not understand reason why the value of user is
   no longer available). However, the 'type' attribute
   provided, it user's server MUST consider NOT depend on
   receiving final presence from an available resource, since the message to be
   resource may become unavailable unexpectedly. If the user's server
   detects that one of type "normal".

   Although the 'type' attribute is NOT REQUIRED, user's resources has become unavailable for
   any reason (either gracefully or ungracefully), it is considered
   polite MUST broadcast
   unavailable presence to mirror the type all contacts (1) that are in any replies to a message; furthermore,
   some specialized applications (e.g., a multi-user chat service) MAY
   at their discretion enforce the use of user's
   roster with a particular message subscription type
   (e.g., type='groupchat').

3.3 Specifying of "from" or "both", (2) to whom the
   user has not blocked outbound presence, and (3) from whom the server
   has not received a Message Body

   A message presence error during the user's session; the
   user's server MUST also send that unavailable presence stanza MAY (and often will) contain a child <body/> element
   specifying to any
   entities to which the primary meaning of user has sent directed presence during the message. The content of
   user's session for that resource (if the
   body element MUST be XML character data user has not yet sent
   directed unavailable presence to that entity). Any presence stanza
   with no 'type' attribute and the element MUST NOT
   contain mixed content. If it no 'to' attribute that is necessary to provide the primary
   meaning in an alternate form (e.g., formatted using XHTML), the
   alternate form sent after
   sending directed unavailable presence or broadcasted unavailable
   presence MUST be contained in some other child of broadcasted by the message
   stanza. However, multiple <body/> elements MAY be included server to provide
   the primary meaning in different languages, as long as each such
   element possesses an 'xml:lang' attribute with a distinct value. all subscribers.



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   Example: A message with a body:

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


3.4


4.2 Specifying a Message Subject Availability Status

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

   o  away -- The entity or more child <subject/> elements
   specifying resource is 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").

   Example: Availability status:

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

   If no <show/> element is provided, the topic entity is assumed to be online
   and available.

4.3 Specifying Detailed Status Information

   In conjunction with the  <show/> element, a client MAY provide
   detailed status information by using the <status/> element. The
   content of this element is a natural-language description of the message.
   user's current availability status. The content of the subject status element
   MUST be XML character data and the element MUST NOT contain mixed
   content. Multiple <subject/> <status/> 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@montague.net'
       from='juliet@capulet.com/balcony'

   Example: Detailed status information:

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


4.4 Specifying a Conversation Thread Presence Priority

   A message stanza client MAY contain provide a child <thread/> element specifying the
   conversation thread in which the message is situated, priority for its resource by using the purpose
   of tracking the conversation.
   <priority/> element. The content of the <thread/> this element is
   a random string that an integer whose
   value is generated by the sender in accordance with
   the algorithm specified in XMPP Core [1]; this string SHOULD be
   copied back to the sender in subsequent replies.






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   Example: A threaded conversation:

   <message
       to='romeo@montague.net/orchard'
       from='juliet@capulet.com/balcony'
       type='chat'>
     <body>Art thou not Romeo, between -128 and +127. If a Montague?</body>
     <thread>e0ffe42b28561960c6b12b944a092794b9683a38</thread>
   </message>

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

   <message
       to='romeo@montague.net/orchard'
       from='juliet@capulet.com/balcony'
       type='chat'>
     <body>How cam'st thou hither, tell me, and wherefore?</body>
     <thread>e0ffe42b28561960c6b12b944a092794b9683a38</thread>
   </message> client does not provide the



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4. Exchanging Presence Information

   Exchanging


   priority element in a presence information stanza, its server SHOULD assume that
   the priority value is made relatively straightforward
   within XMPP by using presence stanzas. However, we see here 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
   contrast to the handling Contact Went Offline

   The server MUST maintain a record of messages: although the time at which a client MAY send
   directed presence information user became
   unavailable (whether gracefully or ungracefully). An authorized
   subscriber to another entity, normally that user's presence
   information is sent from a client MAY request the time of last
   activity by sending an IQ stanza to its server (with no 'to'
   address) and then broadcasted the user's bare JID
   (<user@somedomain>) containing an empty <query/> element qualified by
   the server to any entities that are
   subscribed to 'jabber:iq:last' namespace:

   Example: Requesting the presence last active time of an offline user:

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

   If the sending entity. (Note: in entity requesting the
   terminology time of RFC 2778 [5], last activity is an authorized
   subscriber to the only watchers user's presence (i.e., exists in XMPP are
   subscribers.)

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

4.1 Client and Server Responsibilities

   When a client connects to its server, it SHOULD (but value of "from" or "both")
   and the user is NOT REQUIRED
   to) send initial presence not blocking IQ stanzas to and from the server in order to signal its
   availability for communications. As entity (as
   defined herein, in Section 9.12), the initial
   presence server SHOULD return an IQ stanza (1) MUST possess no 'to' address (signalling that it
   is meant to be handled by of
   type "result" with the server on behalf number of seconds since the user) and (2)
   MUST possess no 'type' attribute (signalling user was last
   active:

   Example: Returning 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 the entity requesting the time of last activity is not an
   authorized subscriber to the user's
   availability).

   Upon receiving initial presence from a client, (i.e., does not exist in
   the user's server MUST
   do roster with the following:

   1.  Send presence probes (i.e., presence stanzas whose 'type' 'subscription' attribute is set to a value of "probe") from
   "from" or "both"), the full JID
       (<user@domain/resource>) server MUST return an IQ stanza of the user type
   "error" with an error condition of forbidden:




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   Example: Requester is forbidden to view the bare JID
       (<user@domain>) last active time of any contacts 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 which the user is subscribed
       in order requests for last active
   time only with regard to determine if they are available; such contacts are
       those which are present in JIDs of the user's roster form <user@somedomain>, and only
   with the
       'subscription' attribute set regard to a value JIDs that correspond to an (offline) instant messaging
   user. The behavior of "to" other JID forms (e.g., <user@somedomain/
   resource> or "both". (Note:
       a <somedomain>) and entity types (e.g., online user or client SHOULD NOT send presence probes.)

   2.  Broadcast initial presence from the full JID (<user@domain/
       resource>)
   host) is out of scope and undefined.

4.6 Presence Examples

   The examples in this section illustrate the presence-related
   protocols described above. The user to is romeo@example.net, he has
   authorized a resource "orchard", and he has the bare JID (<user@domain>) of any
       contacts that are subscribed following individuals
   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/>















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   Example 2: User's server sends presence probe to the user's presence; such contacts are those which are present in with
   subscription="to" and subscription="both" on behalf of the user's roster
   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 'subscription' attribute set 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 replies to a value of "from" or "both".

   Upon receiving a presence probe from the user, 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
   MUST send delivers user's initial presence to all
   of the contact's available resources or returns error to user:

   <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>





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   Example 6: User sends directed presence to another user the last known availability 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 (i.e., for
   broadcasting:

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

   Example 8: Updated presence information is delivered only to one
   contact (not those from whom an error was received or to whom the full XML
   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 last contact's resources sends final presence:

   <presence type='unavailable'/>





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

   <presence
       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) provided by each of the information is delivered to
   contact's active sessions (if there exist no active sessions, one remaining resource as well as to the
   server SHOULD NOT reply person to whom the presence probe). The server MUST send
   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>
   </presence>



















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   this information subject


5. Managing Subscriptions

   In order to domain-specific access rules, and only if
   the user is in protect the contact's roster with a subscription state privacy of
   "from" or "both" instant messaging users and the contact has not blocked outbound any
   other entities, presence
   notifications and availability information is disclosed
   only to other entities that the user's bare or full JID (as defined in Section
   8.11). (Note: if the server receives a presence probe from user has approved. When a
   subdomain of the server's hostname or another such trusted service,
   it MAY provide presence information about the user to has
   agreed that entity.)

   Upon receiving initial presence from the user, another entity may view its presence, the contact's server
   MUST deliver entity is said
   to have a subscription to the user's presence stanza to the full JIDs
   (<contact@domain/resource>) associated with all of information. A
   subscription lasts across sessions; indeed, it lasts until the contact's
   active sessions, but only if
   subscriber unsubscribes or the user is in subscribee cancels the contact's roster with
   a subscription state of "to" or "both"
   previously-granted subscription. Subscriptions are managed within
   XMPP by sending presence stanzas containing specially-defined
   attributes.

   Note: there are important interactions between subscriptions and the contact has not
   blocked inbound presence notifications from the user's bare or full
   JID (as
   rosters; these are defined in Section 8.10).

   If the user's server receives a presence stanza under Integration of type "error" in
   response to Roster Items and
   Presence Subscriptions (Section 7), and the initial presence that it forwarded reader must refer to that
   section for a contact on
   behalf complete understanding of the user, it SHOULD NOT send further presence updates to
   that contact (until and unless it receives subscriptions.

5.1 Requesting a Subscription

   A request to subscribe to another entity's 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 is made by
   sending a 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 type "subscribe".

   Example: Sending a presence update subscription request:

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

   If the subscription request is being sent to broadcast information
   that changes independently of another instant
   messaging user, the user's presence and availability.)
   If JID supplied in the presence stanza lacks a 'type' 'to' attribute (i.e., expresses
   availability), SHOULD be of
   the form <contact@otherdomain> rather than <contact@otherdomain/
   resource>.

   A user's server MUST broadcast the full XML of that
   presence stanza to all contacts (1) that are in NOT automatically accept subscription requests
   on the user's roster
   with a behalf. All subscription type of "from" or "both", (2) requests MUST be directed 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. client. If there is no available resource associated with
   the user when the
   presence stanza has a 'type' attribute set to a value of
   "unavailable", subscription request is received by the server, the
   user's server MUST broadcast the full XML of that
   presence stanza to all contacts meeting store the three conditions just
   mentioned, as well as to any entities to which subscription request offline for
   delivery when the user next becomes available. (Note: if a resource
   has sent
   directed available presence during the user's authorized a session (if the user but has not yet sent directed unavailable presence provided initial presence, the
   server SHOULD NOT consider it to that entity).

   A user MAY be available and therefore SHOULD
   NOT send directed presence subscription requests to it.)

5.2 Handling a Subscription Request

   When a client receives a subscription request from another entity (i.e., entity, it
   MUST either accept the request by sending a presence stanza with a 'to' attribute whose value is the JID of the other
   entity and with either no 'type' attribute type
   "subscribed" or decline the request by sending a 'type' attribute
   whose value is "unavailable"). There are three possible cases:

   1. presence stanza of
   type "unsubscribed".



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   Example: Accepting a subscription request:

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

   Example: Denying a presence subscription request:

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


5.3 Cancelling a Subscription from Another Entity

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

   Example: Cancelling a contact that is in previously granted subscription request:

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


5.4 Unsubscribing from Another Entity's Presence

   If a user would like to unsubscribe from the
       user's roster with presence of another
   entity, it sends a subscription type presence stanza of "from" or "both" after type "unsubscribe".

   Example: Unsubscribing from an entity's presence:

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
























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       having sent initial presence and before sending unavailable
       presence broadcast, the user's server MUST route or deliver the
       full XML


6. Managing One's Roster

   In XMPP, one's contact list is called a roster, which consists of that presence stanza (subject to privacy rules) but
       SHOULD NOT otherwise modify the contact's status regarding
       presence broadcast (i.e., it SHOULD include the contact's JID in any subsequent presence broadcasts initiated by the user).

   2.  If the user sends directed presence to an entity that is not in
       the user's
   number of specific roster with items, each roster item being identified by
   a subscription type unique JID (usually of "from" or "both"
       after having sent initial presence and before sending unavailable
       presence broadcast, the form <contact@otherdomain>). A user's server MUST route or deliver the
       full XML of that presence stanza 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 in any
       subsequent broadcasts of available presence initiated
   roster is stored by the
       user); however, if the connected resource from which the user
       sent the directed presence become unavailable, the user's server
       MUST broadcast that unavailable presence to the entity (if on the
       user has not yet sent directed unavailable presence to user's behalf so that
       entity).

   3.  If
   the user sends directed presence without ever first sending
       initial presence or after having sent unavailable presence
       broadcast, 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 7), and the user's reader must refer to
   that section for a complete understanding of roster management.

   Note: a server MUST ignore any 'to' address on a roster "set", and
   MUST treat the entities any roster "set" as applying 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 a server, sender. For added
   safety, a client SHOULD gracefully
   become unavailable by sending check the "from" address of a final presence stanza that possesses
   no 'to' attribute and roster "push"
   to ensure that possesses a 'type' attribute whose value it is "unavailable" (optionally, from a trusted source; specifically, the final presence stanza MAY contain
   one
   should have no 'from' attribute (i.e., implicitly from the server) or more <status/> elements specifying
   the reason why JID contained in the user is
   no longer available). However, 'from' attribute should match the user's server MUST NOT depend
   bare JID or full JID; otherwise, the client SHOULD ignore the roster
   "push".

6.1 Retrieving One's Roster on
   receiving final presence from an available resource, since Login

   Upon connecting to the
   resource may become unavailable unexpectedly. If server, a client SHOULD request the user's server
   detects that one of roster
   (however, because receiving the user's resources has become unavailable roster may not be desirable for
   any reason (either gracefully or ungracefully), it MUST broadcast
   unavailable presence to all contacts (1) that are in the user's
   roster with
   resources, e.g., a subscription type of "from" or "both", (2) to whom connection with limited bandwidth, the
   user has not blocked outbound presence, and (3) from whom client's
   request for the server
   has roster is NOT REQUIRED). If an available resource
   does not received a presence error during request the user's session; roster during a session, the
   user's server MUST also SHOULD NOT
   send that unavailable presence stanza to any
   entities to which the user has sent directed presence during the
   user's session for that resource (if the user has not yet sent
   directed unavailable it presence to that entity).

4.2 Specifying Availability Status subscriptions and associated "roster pushes".

   Example: Client requests current roster from server:

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















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   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


   Example: Client receives roster from the show element are:

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

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

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

   o  dnd -- The entity item to his or resource is busy (dnd = "Do Not Disturb"). her roster.

   Example: Availability status:

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

   If no <show/> element is provided, Client adds a new item:

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

   The value of the entity is assumed to 'jid' attribute SHOULD be online
   and available.

4.3 Specifying Detailed Status Information

   In conjunction of the form
   <user@somedomain>, especially if the item is associated with another
   (human) instant messaging user.

   The server MUST update the  <show/> element, a client MAY provide
   detailed status roster information by using in persistent storage,
   and also push the <status/> element. The
   content of this element is a natural-language description change out to all of the user's current availability status. The content available resources



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   that have requested the roster. This "roster push" consists of an IQ
   set from the status element
   MUST be XML character data and server to the element MUST NOT contain mixed
   content. Multiple <status/> elements MAY be included, as long as each
   such element possesses an 'xml:lang' attribute client and enables all available resources
   to remain in sync with a distinct value. the server-based roster information.

   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 Server (1) pushes the
   <priority/> element. The content of this element is an integer whose
   value is between -128 updated roster information to all
   available resources and +127. If (2) replies with an IQ result to the sending
   resource:

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

   <iq type='set'>
     <query xmlns='jabber:iq:roster'>
       <item
           name='Nurse'
           jid='nurse@example.com'
           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'/>
   <iq
       from='juliet@example.com/chamber'
       to='example.com'
       type='result'/>


6.3 Updating a client does not provide Roster Item

   Updating an existing roster item (e.g., changing the
   priority element group) is done
   in the same way as adding a presence stanza, its server SHOULD assume that new roster item, i.e., by sending the priority value is zero.



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   roster item in an IQ set to the server.

   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 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 Contact Went Offline

   The roster item, when updating a roster item the server
   MUST maintain update the roster information in persistent storage, and also
   initiate a record "roster push" to all of the time at which user's available resources
   that have requested the roster.

6.4 Deleting a Roster Item

   At any time, a user became
   unavailable (whether gracefully or ungracefully). An authorized
   subscriber to MAY delete an item from its roster by doing an IQ
   set and making sure that the value of the 'subscription' attribute is
   "remove" (a compliant server MUST ignore any other values of 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 roster item, when deleting a roster item the server
   MUST update the roster information in persistent storage, initiate a
   "roster push" to all of the user's presence MAY request available resources that have
   requested the time roster (with the 'subscription' attribute set to a
   value of "remove"), and send an IQ result to the initiating resource.

   For further information about the implications of this command, see
   Section 7.6.





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7. Integration of last
   activity Roster Items and Presence Subscriptions

7.1 Overview

   Some level of integration between roster items and presence
   subscriptions is normally expected by sending an IQ stanza to instant messaging user
   regarding the user's bare JID
   (<user@domain>) containing an empty <query/> element qualified by the
   'jabber:iq:last' namespace:

   Example: Requesting subscriptions to and from other contacts. This
   section describes the last active time level of an offline user:

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

   If integration that must be supported
   within XMPP IM.

   There are four primary subscription states:

   o  None -- Neither the entity requesting user nor the time of last activity contact is an authorized
   subscriber subscribed to the user's
      other's presence (i.e., exists in

   o  To -- The user is subscribed to the user's roster
   with contact's presence but there
      is no subscription from the 'subscription' attribute set contact to a value of "from" or "both")
   and the user

   o  From -- There is a subscription from the contact to the user, but
      the user has not blocking IQ stanzas subscribed to the contact's presence

   o  Both -- Both the user and from the entity (as
   defined in Section 8.12), contact are subscribed to each
      other's presence (i.e., the server SHOULD return an IQ stanza union of
   type "result" with the number 'from' and 'to')

   Each of seconds since the user was last
   active:

   Example: Returning these states is reflected in the last active time roster of an offline user:

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

   If both the entity requesting user and
   the time contact, thus resulting in durable subscription states. A
   detailed explanation of last activity is not an
   authorized subscriber to how these subscription states interact with
   roster items is provided in the user's presence (i.e., following sub-sections.

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

   The 'from' and 'to' addresess are OPTIONAL in roster with pushes; if
   included, their values SHOULD be the 'subscription' attribute set to a value full JID of
   "from" or "both"), the server resource for
   that session. A client MUST return acknowledge each "roster push" with an IQ
   stanza of type
   "error" with an error condition of forbidden:







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

   <iq from='user@domain' type='error' to='subscriber@domain/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 of "result" (for the form <user@domain>, and only
   with regard to JIDs that correspond to an (offline) instant messaging
   user. The behavior of other JID forms (e.g., <user@domain/resource>
   or <domain>) and entity types (e.g., online user or host) is out sake of
   scope and undefined.

4.6 Presence Examples

   The examples brevity, these stanzas are
   not shown in this section illustrate the presence-related
   protocols described above. following examples but are required by XMPP Core
   [1]).

7.2 User Subscribes to Contact

   The process by which a user is romeo@montague.net, he has
   authorized subscribes to a resource "orchard", and he has contact, including the following individuals
   in his roster:

   o  juliet@capulet (subscription="both"
   interaction between roster items and she has two active
      sessions, one whose resource subscription states, is "chamber" defined
   below.

   1.  In preparation for being able to render the contact in the user's
       client interface and another whose
      resource is "balcony")

   o  benvolio@shakespeare.lit (subscription="to")

   o  mercutio@verona.it (subscription="from")

   Example 1: User sends initial presence:

   <presence/> for the server to keep track of the



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   Example 2: User's server sends presence probe to contacts with
   subscription="to" and subscription="both" on behalf


       subscription, the user's client SHOULD perform a "roster set" 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; 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
   connected resource:

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

   <presence
       type='probe'
       from='romeo@montague.net/orchard'
       to='benvolio@shakespeare.lit'/>

   Example 3: User's server sends initial presence (1) MUST initiate a "roster push"
       for the new roster item to contacts all available resources associated
       with
   subscription="from" this user that have requested the roster, setting the
       'subscription' attribute to a value of "none"; and subscription="both" on behalf (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 the user's
   connected resource:

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

   <presence
       from='romeo@montague.net/orchard'
       to='mercutio@verona.it'/>


























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   Example 4: Contacts' server replies user wants to request a subscription to the contact's
       presence, the user's client MUST send a presence probe on behalf of
   all stanza of
       type='subscribe' to the contact's available resources:

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

   <presence
       from='juliet@capulet.com/chamber'
       to='romeo@montague.net/orchard'>
     <priority>1</priority>
   </presence> contact:

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

   Example 5: Contact's server delivers to='contact@otherdomain' type='subscribe'/>

   4.  As a result, the user's initial presence server MUST initiate a second "roster
       push" to all of the contact's user's available resources or returns error that have
       requested the roster, setting the contact to user:

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

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

   <presence
       type='error'
       from='mercutio@verona.it'
       to='romeo@montague.net/orchard'>
     <error type='cancel'>
       <remote-server-not-found
           xmlns='urn:ietf:params:xml:ns:xmpp-stanzas'/>
     </error>
   </presence> the pending
       sub-state of the 'none' subscription state; this pending



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   Example 6: User sends directed presence to another


       sub-state is denoted by the inclusion of the ask='subscribe'
       attribute in 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 user did not in his
   roster:

   <presence
       from='romeo@montague.net/orchard'
       to='nurse@capulet.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 xml:lang='en'>
     <show>away</show>
     <status>I shall return!</status>
     <priority>1</priority>
   </presence>

   Example 8: Updated presence information is delivered only to create a roster item before sending the
       subscription request, the server MUST now create one
   contact (not those from whom an error was received or and send a
       "roster push" to whom all of the
   user sent directed presence):

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

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

   Example 9: One user's available resources that have
       requested the roster, absent the 'name' attribute and the <group/
       > child.

   5.  The user's server MUST also stamp the presence stanza 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 contact's resources sends final presence:

   <presence type='unavailable'/>





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

   <presence
       type='unavailable'
       from='juliet@capulet.com/balcony'
       to='romeo@montague.net/orchard'/>

   Example 11: User sends final presence:

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

   Example 12: Unavailable MUST route the presence information is delivered stanza
       to the contact's one remaining resource as well as server for delivery to the person to whom contact (this case is
       assumed throughout; however, if the
   user sent directed presence:

   <presence
       type='unavailable'
       from='romeo@montague.net/orchard'
       to='juliet@capulet.com/chamber'
       xml:lang='en'>
     <status>gone home</status>
   </presence> contact is served by the same
       host, then the server can simply deliver the presence stanza
       directly):

   <presence
       from='romeo@montague.net/orchard'
       to='nurse@capulet.com'
       xml:lang='en'>
     <status>gone home</status>
   </presence>



















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5. Managing Subscriptions

   In order to protect
       from='user@somedomain'
       to='contact@otherdomain'
       type='subscribe'/>

   6.  Upon receiving the privacy presence stanza of instant messaging users and any
   other entities, type "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 availability information 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 for
       delivery when this condition is disclosed
   only next met). No matter when the
       subscription request is delivered, the contact must decide
       whether or not to other entities that accept it (subject to configured preferences,
       the user has approved. When a user has
   agreed that another entity may view its presence, contact's client MAY accept or deny the entity is said
   to have a subscription request
       without presenting it to the user's presence information. A
   subscription lasts across sessions; indeed, it lasts until contact). Here we assume the
   subscriber unsubscribes or "happy
       path" that the subscribee cancels contact accepts the
   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 subscription request (the
       alternate flow of Roster Items and
   Presence Subscriptions (Section 7), and declining the reader must refer to that
   section for a complete understanding of presence subscriptions.

5.1 Requesting a Subscription

   A subscription request to subscribe to another entity's presence is made by
   sending defined



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       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 presence stanza of type "subscribe".

   Example: Sending a subscription request:

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

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

   A user's server MUST NOT automatically order to accept subscription requests
   on the user's behalf. All subscription requests
       request.

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

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

   7.  As a result, the contact's server (1) MUST be directed initiate a "roster
       push" to
   the user's client. If there is no all available resource resources associated with the user when the subscription request is received by the server, the
   user's server MUST store contact that
       have requested the subscription request offline roster, containing a roster item for
   delivery when the user next becomes available. (Note: if a resource
   has authorized a session but has not provided initial presence,
       with the
   server SHOULD NOT consider it to be available and therefore SHOULD
   NOT send subscription requests state set to it.)

5.2 Handling a Subscription Request

   When a client receives a subscription request from another entity, it 'from'; (2) MUST either accept route the request by sending a
       presence stanza of type "subscribed" or decline to the 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='user@somedomain'
           subscription='from'
           name='SomeUser'>
         <group>SomeGroup</group>
       </item>
     </query>
   </iq>

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

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

   8.  Upon receiving the request by sending a presence stanza of type "unsubscribed". "subscribed" addressed
       to the user, the user's server MUST first verify that the contact



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   Example: Accepting a subscription request:

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

   Example: Denying a presence subscription request:

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


5.3 Cancelling a Subscription from Another Entity


       is in the user's roster with either of the following states: (a)
       subscription='none', ask='subscribe' or (b) subscription='from',
       ask='subscribe'. If a user would like to cancel a previously-granted subscription
   request, it sends a the contact is not in the user's roster with
       either of those states, the user's server MUST silently ignore
       the presence stanza of type "unsubscribed".

   Example: Cancelling a previously granted subscription request:

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


5.4 Unsubscribing from Another Entity's Presence

   If "subscribed" (i.e., it MUST NOT route
       it to the user, modify the user's roster, or generate a user would like roster
       push to unsubscribe from the presence of another
   entity, it sends a user's available resources). If the contact is in the
       user's roster with either of those states, the user's server (1)
       MUST deliver the presence stanza of type "unsubscribe".

   Example: Unsubscribing "subscribed" from an entity's presence:

   <presence to='juliet@capulet.com' type='unsubscribe'/>
























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6. Managing One's Roster

   In XMPP, one's the
       contact list is called to the user; (2) MUST initiate a roster, which consists of any
   number "roster push" to all of specific roster items, each
       the user's available resources that have requested the roster,
       containing an updated roster item being identified by for the contact with the
       'subscription' attribute set to a unique JID (usually value of "to"; and (3) MUST
       deliver the form <contact@domain>). A user's roster
   is stored by available presence stanza received from each of the user's server on
       contact's available resources to each of the user's behalf so that the user
   may access roster information from any available resource.

   Note: there are important interactions between rosters and
   subscriptions; these are defined under Integration
       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 the presence stanza of Roster Items
   and Presence Subscriptions (Section 7), and type "subscribed", the reader must refer to user
       SHOULD acknowledge receipt of that section for subscription state
       notification through either accepting it by sending a complete understanding presence
       stanza of roster management.

6.1 Retrieving One's Roster on Login

   Upon connecting type "subscribe" to the server, contact or denying it by
       sending a client SHOULD request presence stanza of type "unsubscribe" to the roster
   (however, because receiving contact;
       this step lets the roster may not be desirable for all
   resources, e.g., a connection with limited bandwidth, user's server know that it must no longer send
       notification of the client's
   request for subscription state change to the roster is NOT REQUIRED). If an available resource
   does not request user (see
       Section 8.6).

   From the roster during perspective of the user, there now exists a session, subscription to
   the server SHOULD NOT
   send it presence subscriptions and associated "roster pushes".

   Example: Client requests current roster contact; from server:

   <iq type='get' id='roster_1'>
     <query xmlns='jabber:iq:roster'/>
   </iq> the perspective of the contact, there now exists a



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   Example: Client receives roster


   subscription from the server:

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


6.2 Adding a Roster Item

   At any time, a user. (Note: If at this point the user MAY add an item sends
   another subscription request to his or her roster.

   Example: Client adds a new item:

   <iq type='set' id='roster_2'>
     <query xmlns='jabber:iq:roster'>
       <item
           name='Nurse'
           jid='nurse@capulet.com'>
         <group>Servants</group>
       </item>
     </query>
   </iq> the contact, the user's server MUST
   silently ignore that request.)

7.2.1 Alternate Flow: Contact Declines Subscription Request

   The value 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 denies the user's subscription request.

   1.  If the contact wants to deny 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 7.2):

   <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 'jid' attribute SHOULD be contact:

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

   3.  Upon receiving the presence stanza of type "unsubscribed"
       addressed to the form <user@domain>,
   especially if user, the item is associated with another (human) instant
   messaging user.

   The user's server (1) MUST update deliver that
       presence stanza to the roster information in persistent storage, user and also push the change out (2) MUST initiate a "roster push"
       to all of the user's available resources



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       roster, containing an IQ
   set from the server to updated roster item for the client and enables all available resources
   to remain in sync contact with
       the server-based roster information.

   Example: Server (1) pushes the updated roster information 'subscription' attribute set to all
   available resources a value of "none" and (2) replies with an IQ result to the sending
   resource:

   <iq type='set'>
     <query xmlns='jabber:iq:roster'>
       <item
           name='Nurse'
           jid='nurse@capulet.com'
           subscription='none'>
         <group>Servants</group>
       </item>
     </query>
   </iq> no
       'ask' attribute:

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

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



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   </iq>

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

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

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


6.3 Updating a Roster Item

   Updating an existing roster item (e.g., changing

   4.  Upon receiving the group) is done
   in presence stanza of type "unsubscribed", the same way as adding
       user SHOULD acknowledge receipt of that subscription state
       notification through either accepting it by sending a new roster item, i.e., presence
       stanza of type "unsubscribe" to the contact or denying it by
       sending a presence stanza of type "subscribe" to the contact;
       this step lets the user's server know that it must no longer send
       notification of the



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   roster item in an IQ set subscription state change to the server.

   Example: User updates roster item (added group):

   <iq type='set' id='roster_3'>
     <query xmlns='jabber:iq:roster'>
       <item
           jid='romeo@montague.net'
           name='Romeo'
           subscription='both'>
         <group>Friends</group>
         <group>Lovers</group>
       </item>
     </query>
   </iq> user (see
       Section 8.6).

   As with adding a roster item, when updating a roster item result of this activity, the server
   MUST update contact is now in the user's roster information in persistent storage, and also
   initiate
   with a "roster push" to all subscription state of "none", whereas the user's available resources
   that have requested user is not in the roster.

6.4 Deleting a Roster Item

   At any time,
   contact's roster at all.

7.3 Creating a Mutual Subscription

   The user MAY delete an item from its roster by doing an IQ
   set and making sure that contact can build on the value foregoing to create a mutual
   subscription (i.e., a subscription of the 'subscription' attribute type "both"). The process is
   "remove" (a compliant server MUST ignore any other values of
   defined below.

   1.  If the
   'subscription' attribute when received from contact wants to create a client).

   Example: Client removes an item:

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

   As with adding mutual subscription, the contact
       MUST send a roster item, when deleting subscription request to the user (subject to
       configured preferences, the contact's client MAY send this
       automatically):

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

   2.  As a roster item result, the contact's server (1) MUST update the roster information in persistent storage, initiate a "roster
       push" to all available resources associated with the contact that
       have requested the roster, with the user still in the 'from'
       subscription state but with a pending 'to' subscription denoted
       by the inclusion of the user's available resources that have
   requested ask='subscribe' attribute in the roster (with
       item; and (2) MUST route the 'subscription' attribute set to a
   value presence stanza of "remove"), and send an IQ result type "subscribe"
       to the initiating resource.

   For further information about user, first stamping the implications 'from' address as the bare JID
       (<contact@otherdomain>) of this command, see
   Section 7.6. the contact:















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7. Integration of Roster Items and Presence Subscriptions

7.1 Overview

   Some level of integration between roster items and presence
   subscriptions is normally expected by an instant messaging user
   regarding


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

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

   3.  Upon receiving the user's subscriptions presence stanza of type "subscribe" addressed
       to and from other contacts. This
   section describes the level of integration that user, the user's server must be supported
   within XMPP IM.

   There are four primary subscription states:

   o  None -- Neither determine if there is at
       least one active session in which the user nor has sent available
       presence and has requested the contact is subscribed to roster. If so, the
      other's presence

   o  To -- The user is subscribed to user's server
       MUST deliver the contact's presence but there
      is no subscription from the contact request to the user

   o  From -- There is a subscription from (if not, it
       MUST store the contact to subscription request offline for delivery when
       this condition is next met). No matter when the user, but subscription
       request is delivered, the user has must then decide whether or not subscribed to
       accept it (subject to configured preferences, the contact's presence

   o  Both -- Both the user and user's client
       MAY accept or deny the contact are subscribed subscription request without presenting it
       to each
      other's presence (i.e., the union of 'from' and 'to')

   Each of these states is reflected in user). Here we assume the roster of both "happy path" that the user and
       accepts the contact, thus resulting in durable subscription states. A
   detailed explanation request (the alternate flow of how these declining
       the subscription states interact with
   roster items request is provided defined in Section 7.3.1). In this
       case, the following sub-sections.

   If a connected resource does not both user's client MUST send initial a presence and
   request the roster, stanza of type
       "subscribed" to the server SHOULD NOT send it presence
   subscription requests or "roster pushes".

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

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

   4.  As a result, the resource for
   that session. A client user's server (1) MUST acknowledge each initiate a "roster push" with an IQ
   stanza
       to all of type "result" (for the sake of brevity, these stanzas are
   not shown in user's available resources that have requested the following examples but are required by XMPP Core
   [1]).

7.2 User Subscribes to Contact

   The process by which
       roster, containing a user subscribes roster item for the contact with the
       'subscription' attribute set to a contact, including value of "both"; (2) MUST route
       the
   interaction between roster items and subscription states, is defined
   below.

   1.  In preparation for being able presence stanza of type "subscribed" to render the contact in contact, first
       stamping the 'from' address as the bare JID (<user@somedomain>)
       of the user; and (3) MUST send available presence from each of
       the user's
       client interface and for the server available resources to keep track of the contact:







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       subscription, the user's client SHOULD perform a "roster set" for


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

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

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

   5.  Upon receiving the new roster item. This request consists of an IQ presence stanza of
       type='set' containing a <query/> element type "subscribed" addressed
       to the contact, the contact's server MUST first verify that the
       user is in the
       'jabber:iq:roster' namespace, which 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 in turn contains an <item/>
       element that defines the new
       contact's roster item; with either of those states, the <item/> element contact's
       server MUST possess a 'jid' attribute, MAY possess a 'name' attribute, silently ignore the presence stanza of type
       "subscribed" (i.e., it MUST NOT possess a 'subscription' attribute, and MAY contain one route it to the contact, modify
       the contact's roster, or more <group/> child elements:

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

   2.  As generate a result, roster push to the user's contact's
       available resources). If the user is in the contact's roster with
       either of those states, the contact's server (1) MUST deliver the
       presence stanza of type "subscribed" from the user to the
       contact; (2) MUST initiate a "roster push"
       for the new roster item to all available
       resources associated with this user the contact that have requested the
       roster, setting containing an updated roster item for the user with the
       'subscription' attribute set to a value of "none"; "both"; and (2) (3) MUST reply
       with an IQ
       deliver the available presence stanza received from each of type='result': the
       user's available resources to each of the contact's available
       resources:












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

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

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

   3.  If

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

   6.  Upon receiving the user wants to request a presence stanza of type "subscribed", the
       contact SHOULD acknowledge receipt of that subscription state
       notification through either accepting it by sending a presence
       stanza of type "subscribe" to the contact's
       presence, the user's client MUST send user or denying it by sending a
       presence stanza of
       type='subscribe' type "unsubscribe" to the contact:

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

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

   The user and the contact now have a result, mutual subscription to each
   other's presence -- i.e., the subscription is of type "both". The
   user's server MUST initiate now send the user's current presence information
   to the contact. (Note: If at this point the user sends a second "roster
       push" subscription
   request to all of the contact or the contact sends a subscription request to
   the user, the sending user's available resources server MUST silently ignore that have
       requested request
   and not route it to the roster, setting intended recipient.)

7.3.1 Alternate Flow: User Declines Subscription Request

   The above activity flow represents the contact "happy path" related to the pending
       sub-state of the 'none'
   contact's subscription state; this pending



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       sub-state is denoted by request to the inclusion of user. The main alternate flow
   occurs if the ask='subscribe'
       attribute in user denies the roster item:

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

       Note: if contact's subscription request.

   1.  If the user did not create a roster item before sending wants to deny the
       subscription request, the server user's client MUST now create one and
       send a
       "roster push" to all presence stanza of type "unsubscribed" to the user's available resources that have
       requested the roster, absent the 'name' attribute and the <group/
       > child.

   5.  The user's server MUST also stamp contact
       (instead of the presence stanza of type
       "subscribe" with the user's bare JID (i.e., <user@domain>) as the
       'from' address. If the contact is served by "subscribed" sent in Step
       3 of Section 7.3):




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

   2.  As a different host than
       the user, result, the user's server MUST route the presence stanza of
       type "unsubscribed" to the
       contact's server for delivery to the contact (this case is
       assumed throughout; however, if the contact is served by contact, first stamping the same
       host, then 'from'
       address as the server can simply deliver bare JID (<user@somedomain>) of the presence stanza
       directly): user:

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

   6.
       from='user@somedomain'
       to='contact@otherdomain'
       type='unsubscribed'/>

   3.  Upon receiving the presence stanza of type "subscribe" "unsubscribed"
       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 (1) MUST deliver
       that presence stanza to the subscription request contact; and (2) MUST initiate a
       "roster push" to all available resources associated with the
       contact (if not, the
       contact's server MUST store that have requested the subscription request offline roster, containing an updated
       roster item for
       delivery when this condition is next met). No matter when the
       subscription request is delivered, user with the 'subscription' attribute set to
       a value of "from" and 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='from'
           name='SomeUser'>
         <group>SomeGroup</group>
       </item>
     </query>
   </iq>

   4.  Upon receiving the presence stanza of type "unsubscribed", the
       contact must decide
       whether or not SHOULD acknowledge receipt of that subscription state
       notification through either accepting it by sending a presence
       stanza of type "unsubscribe" to accept the user or denying it (subject by sending
       a presence stanza of type "subscribe" to configured preferences, the user; this step lets
       the contact's client MAY accept or deny server know that it must no longer send
       notification of the subscription request
       without presenting it state change to the contact). Here we assume contact (see
       Section 8.6).

   As a result of this activity, there has been no change in the "happy
       path" that
   subscription state; i.e., the contact accepts is in the user's roster with a
   subscription request (the
       alternate flow state of declining "to" and the subscription request user is defined in the contact's roster
   with a subscription state of "from".



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7.4 Unsubscribing

   At any time after subscribing to a contact's presence, a user MAY
   unsubscribe. While the XML that the user sends to make this happen is
   the same in Section 7.2.1). 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.

7.4.1 Case #1: Unsubscribing When Subscription is Not Mutual

   In this the first case, the contact's client (1) SHOULD
       perform user has a roster set specifying subscription to the desired nickname and group
       for contact but the user; and (2)
   contact does not have a subscription to the user (i.e., the
   subscription is not yet mutual).

   1.  If the user wants to unsubscribe from the contact's presence, the
       user MUST send a presence stanza of type
       "subscribed" to the user in order "unsubscribe" to accept the subscription
       request.

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

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

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

   2.  As a result, the contact's user's server (1) MUST initiate send a "roster push" to
       all of the user's available resources associated with the contact that have requested the
       roster, containing a an updated roster item for the user contact with
       the subscription state 'subscription' attribute set to 'from'; a value of "none"; and (2)
       MUST route the presence stanza of type "subscribed" "unsubscribe" to the user; and (3) MUST
       send available presence from all of
       contact, first stamping the contact's available
       resources to 'from' address as the bare JID
       (<user@somedomain>) of the user:

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

   <presence
       from='contact@domain/resource'
       to='user@domain'
       type='subscribed'/>

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

   8.
       from='user@somedomain'
       to='contact@otherdomain'
       type='unsubscribe'/>

   3.  Upon receiving the presence stanza of type "subscribed" "unsubscribe"
       addressed to the user, contact, the user's contact's server (1) MUST first verify that initiate
       a "roster push" to all available resources associated with the contact



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       is in


       contact that have requested the user's roster, containing an updated
       roster item for the user with either of the following states: (a)
       subscription='none', ask='subscribe' or (b) subscription='from',
       ask='subscribe'. If 'subscription' attribute set to
       a value of "none" (if the contact is not in offline, the contact's
       server MUST modify the user's roster with
       either of those states, item and send that modified item
       the user's server next time the contact requests the roster); and (2) MUST silently ignore
       deliver the "unsubscribe" state change 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='unsubscribe'/>

   4.  Upon receiving the presence stanza of type "subscribed" (i.e., it MUST NOT route
       it to the user, modify the user's roster, or generate a roster
       push to the user's available resources). If "unsubscribe", the
       contact is in the
       user's roster with SHOULD acknowledge receipt of that subscription state
       notification through either accepting it by sending a presence
       stanza of those states, the user's server (1)
       MUST deliver type "unsubscribed" to the user or denying it by
       sending a presence stanza of type "subscribed" from the
       contact to the user; (2) MUST initiate a "roster push" to all of this
       step lets the user's available resources contact's server know that have requested it must no longer send
       notification of the roster,
       containing an updated roster item for subscription state change to the contact with the
       'subscription' attribute set to (see
       Section 8.6).

   5.  The contact's server then (1) MUST send a value presence stanza of "to"; and (3) MUST
       deliver type
       "unsubscribed" to the available user; and (2) SHOULD send unavailable
       presence stanza received from each of the
       contact's available resources contact to each of the user's available
       resources: user:

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

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

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

   From the perspective of
       from='contact@otherdomain'
       to='user@somedomain'
       type='unavailable'/>





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   6.  When the user, there now exists user's server receives a subscription presence stanza of type
       "unsubscribed" and/or unavailable presence, it MUST deliver them
       to the contact; from user:

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

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

   7.  Upon receiving the perspective presence stanza of the contact, there now exists a
   subscription from the user. (Note: If at this point type "unsubscribed", the
       user sends
   another SHOULD acknowledge receipt of that subscription request state
       notification through either accepting it by sending a presence
       stanza of type "unsubscribe" to the contact, contact or denying it by
       sending a presence stanza of type "subscribe" to the contact;
       this step lets the user's server MUST
   silently ignore know that request.)

7.2.1 Alternate Flow: Contact Declines Subscription Request

   The above activity flow represents it must no longer send
       notification of the "happy path" related subscription state change to the
   user's user (see
       Section 8.6).


7.4.2 Case #2: Unsubscribing When Subscription is Mutual

   In the second case, the user has a subscription request to the contact. The main alternate flow
   occurs if contact and
   the contact denies also has a subscription to the user (i.e., the user's
   subscription request.



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

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

   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@domain>) of the contact:

   <presence
       from='contact@domain'
       to='user@domain'
       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 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 "none" "from"; and with no
       'ask' attribute:

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

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

   As a result of this activity, the contact is now in (2)
       MUST route the user's roster
   with a subscription state presence stanza of "none", whereas type "unsubscribe" to the user is not in
       contact, first stamping the
   contact's roster at all.

7.3 Creating a Mutual Subscription

   The user and contact can build on 'from' address as the foregoing to create a mutual
   subscription (i.e., a subscription bare JID
       (<user@somedomain>) of type "both"). The process is the user:








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   defined below.

   1.  If the contact wants to create a mutual subscription, the contact
       MUST send a subscription request to


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

   3.  Upon receiving the user (subject presence stanza of type "unsubscribe"
       addressed to
       configured preferences, the contact's client MAY send this
       automatically):

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

   2.  As a result, contact, the contact's server (1) MUST initiate
       a "roster push" to all available resources associated with the
       contact that have requested the roster, with containing an updated
       roster item for the user still in the 'from'
       subscription state but with a pending 'to' subscription denoted
       by the inclusion 'subscription' attribute set to
       a value of "to" (if the ask='subscribe' attribute in contact is offline, the contact's server
       MUST modify the roster
       item; item and (2) MUST route send that modified item the presence stanza of type "subscribe"
       to next
       time the user, first stamping contact requests the 'from' address as roster); and (2) MUST deliver the bare JID
       (<contact@domain>) of
       "unsubscribe" state change notification to the contact:

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

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

   3.
       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 accepting 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 lets the contact's server know that it must no longer send



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       notification of the subscription state change to the contact (see
       Section 8.6).

   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
       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 accepting it by sending a presence
       stanza of type "unsubscribe" to the contact or denying it by
       sending a presence stanza of type "subscribe" addressed to the user, contact;
       this step lets the user's server know that it must determine if there is at
       least one active session in which no longer send
       notification of the subscription state change to the user has sent available
       presence and has requested (see
       Section 8.6).

   Note: Obviously this does not result in removal of the roster. If so, roster item
   from the user's server
       MUST deliver roster, and the contact still has a subscription request 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 (if not, it
       MUST store should update the roster item with subscription='remove' as
   defined in Section 7.6.





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7.5 Cancelling a Subscription

   At any time after approving a subscription request offline for delivery when from a user, a
   contact MAY cancel that subscription. While the XML that the contact
   sends to make this condition happen is next met). No matter when the same in all instances, the
   subsequent subscription
       request state is delivered, different depending on the user must then decide whether or not to
       accept it (subject to configured preferences,
   subscription state obtaining when the user's client
       MAY accept or deny cancellation was sent. Both
   possible scenarios are defined below.

7.5.1 Case #1: Cancelling When Subscription is Not Mutual

   In the first case, the user has a subscription request without presenting it to the user). Here we assume contact but the "happy path" that
   contact does not have a subscription to the user
       accepts (i.e., the
   subscription request (the alternate flow of declining is not yet mutual).

   1.  If the subscription request is defined in Section 7.3.1). In this



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       case, contact wants to cancel the user's client subscription, the
       contact MUST send a presence stanza of type
       "subscribed" to the contact in order "unsubscribed" to accept the subscription
       request.
       user:

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

   4. to='user@somedomain' type='unsubscribed'/>

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






















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

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

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

   5.
       from='contact@otherdomain'
       to='user@somedomain'
       type='unavailable'/>

   3.  Upon receiving the presence stanza of type "subscribed" "unsubscribed"
       addressed to the contact, the contact's server MUST first verify that the
       user is in 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 in the
       contact's roster with either of those states, the contact's
       server MUST silently ignore the presence stanza of type
       "subscribed" (i.e., it MUST NOT route it to the contact, modify
       the contact's roster, or generate a roster push to the contact's
       available resources). If the user is in the contact's roster with
       either of those states, user, the contact's user's server (1) MUST deliver the
       presence stanza of type "subscribed" from the user to the
       contact; (2) MUST initiate a
       "roster push" to all of the user's available



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       requested the roster, containing an updated roster item for 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 with
       requests the
       'subscription' attribute set roster); (2) MUST deliver the "unsubscribed" state
       change notification to a value of "both"; the user; and (3) MUST deliver the available
       unavailable presence stanza received from each of the
       user's available resources to each of the contact's available
       resources:

   <presence
       from='user@domain'
       to='contact@domain'
       type='subscribed'/> user:




















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

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

   The user and
       from='contact@otherdomain'
       to='user@somedomain'
       type='unsubscribed'/>

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

   4.  Upon receiving the contact now have a mutual subscription to each
   other's presence -- i.e., the subscription is stanza of type "both". The
   user's server MUST now send the user's current presence information
   to the contact. (Note: If at this point "unsubscribed", the
       user sends a SHOULD acknowledge receipt of that subscription
   request state
       notification through either accepting it by sending a presence
       stanza of type "unsubscribe" to the contact or the contact sends denying it by
       sending a subscription request presence stanza of type "subscribe" to the user, contact;
       this step lets the sending user's server MUST silently ignore know that request
   and not route it to the intended recipient.)

7.3.1 Alternate Flow: User Declines Subscription Request

   The above activity flow represents the "happy path" related to must no longer send
       notification of the
   contact's subscription request state change to the user. The main alternate flow
   occurs if the user denies the contact's subscription request.

   1.  If the user wants to deny the request, the user's client MUST
       send a presence stanza of type "unsubscribed" to the contact
       (instead of the presence stanza of type "subscribed" sent in Step
       3 of (see
       Section 7.3):

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




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   2.  As 8.6).


7.5.2 Case #2: Cancelling When Subscription is Mutual

   In the second case, the user has a result, subscription to the user's server MUST route contact and
   the presence stanza of
       type "unsubscribed" contact also has a subscription to the contact, first stamping user (i.e., the 'from'
       address as
   subscription is mutual).

   1.  If the bare JID (<user@domain>) of contact wants to cancel the user:

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

   3.  Upon receiving user's subscription, the
       contact MUST send a presence stanza of type "unsubscribed"
       addressed to the contact,
       user:

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

   2.  As a result, the contact's server (1) MUST deliver
       that presence stanza to the contact; and (2) MUST initiate send 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 "from" and with no 'ask' attribute:

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

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

   As a result of this activity, there has been no change in the
   subscription state; i.e., the contact is in the user's roster with a
   subscription state of "to" and the user is in "to"; (2) MUST
       route the contact's roster
   with a subscription state presence stanza of "from".

7.4 Unsubscribing

   At any time after subscribing to a contact's presence, a user MAY
   unsubscribe. While the XML that the user sends type "unsubscribed" to 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. user,



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7.4.1 Case #1: Unsubscribing When Subscription is Not Mutual

   In the


       first case, the user has a subscription to the contact but stamping the
   contact does not have a subscription to 'from' address as the user (i.e., bare JID
       (<contact@otherdomain>) of the
   subscription is not yet mutual).

   1.  If contact; and (3) SHOULD send
       unavailable presence from the user wants contact to unsubscribe from the contact's presence, 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
       user MUST send a presence stanza of type "unsubscribe" "unsubscribed"
       addressed to the
       contact:

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

   2.  As a result, user, the user's server (1) MUST send 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";
       "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 route deliver the presence stanza of type "unsubscribe" "unsubscribed"
       state change notification to the
       contact, first stamping the 'from' address as user; and (3) MUST deliver the bare JID
       (<user@domain>) of
       unavailable presence to the user:
















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

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

   3.
       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
       notification through either accepting it by sending a presence
       stanza of type "unsubscribe"
       addressed to the contact, contact or denying it by
       sending a presence stanza of type "subscribe" to the contact's contact;
       this step lets the user's server (1) MUST initiate 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 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 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 push" to all available resources associated with the
       contact that have requested
   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 roster, current subscription state is by sending
   a roster set containing an updated
       roster item for the user contact 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); and (2) SHOULD
       deliver the unsubscribe command to the contact: "remove":






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   <iq type='set'> type='set' id='remove1'>
     <query xmlns='jabber:iq:roster'>
       <item
           jid='user@domain'
           subscription='none'
           name='SomeUser'>
         <group>SomeGroup</group>
       </item>
           jid='contact@otherdomain'
           subscription='remove'/>
     </query>
   </iq>

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

   4.  The contact's server then (1) MAY send a presence stanza of type
       "unsubscribed" to

   When the user; and (2) SHOULD send unavailable
       presence user removes a contact from his or her roster by setting the contact
   'subscription' attribute to the user:

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

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

   5.  If a value of "remove", the user's server receives a presence stanza of type
       "unsubscribed" and/or unavailable presence, it
   (1) MUST deliver them
       to the user:

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

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


7.4.2 Case #2: Unsubscribing When Subscription is Mutual

   In the second case, the user has a automatically cancel any existing presence subscription to
   between the contact user and



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   subscription is mutual).

   1.  If (both 'to' and 'from' as
   appropriate); (2) MUST remove the user wants to unsubscribe roster item from the contact's presence, user's roster
   and inform all of the user's available resources of the
       user roster item
   removal; (3) MUST inform the resource that initiated the removal of
   success; and (4) SHOULD send a unavailable presence stanza of type "unsubscribe" to the contact:

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

   2.  As a result,

   <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 user's presence stanza of type "unsubscribe", the
   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 roster item for the contact user with the
   'subscription' attribute set to a value of "from"; "to" (if the contact is
   offline, the contact's server MUST modify the roster item and (2)
       route send



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   that modified item the presence stanza of type "unsubscribe" to next time the contact,
       first stamping contact requests the 'from' address as roster);
   and (2) MUST also deliver the bare JID (<user@domain>)
       of "unsubscribe" state change notification
   to the user: contact:

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

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

   3.

   Upon receiving the presence stanza of type "unsubscribe"
       addressed to the contact, "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 "to" "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);
   and (2) SHOULD MUST also deliver the
       unsubscribe command "unsubscribe" state change notification
   to the contact:









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

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

   4.  The contact's server then (1) MAY send a
       from='user@somedomain'
       to='contact@otherdomain'
       type='unsubscribed'/>

   Upon receiving the presence stanza of type
       "unsubscribed" to the user; and (2) SHOULD send unavailable
       presence from the contact "unavailable" addressed to
   the user:

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

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

   5.  If contact, the user's contact's server receives a presence stanza of type
       "unsubscribed" and/or unavailable presence, it MUST deliver them the unavailable



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   presence to the user:

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

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

   Note: Obviously this does not result in removal of

   Note that when the user removes the roster item contact from the user's roster, and
   the contact end state of the contact's roster is that the user is still has in
   the contact's roster with a subscription to
   the user's presence. In state of "none"; in order to both
   completely cancel a mutual
   subscription and fully remove the roster item from for the user's roster, user, the contact needs to
   also send a roster removal request.







































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   the user should update the roster item with subscription='remove' as
   defined in Section 7.6.

7.5 Cancelling a


8. Subscription

   At any time after approving States

   This section summarizes information about subscription states.

8.1 Defined States

   There are nine possible subscription states:

   1.  "None" = you and I are not subscribed to each other, and neither
       of us has requested a subscription request from a user, a
   contact MAY cancel that subscription. While the XML that the contact
   sends other

   2.  "None + Pending Out" = you and I are not subscribed to make this happen is the same in all instances, the
   subsequent each
       other, and I've sent you a subscription state is different depending on the request but you have not
       responded yet

   3.  "None + Pending In" = you and I are not subscribed to each other,
       and you've sent me a subscription state obtaining when the cancellation was sent. Both
   possible scenarios request but I have not
       responded yet

   4.  "None + Pending Out/In" = you and I are defined below.

7.5.1 Case #1: Cancelling When Subscription is Not Mutual

   In the first case, the user has not subscribed to each
       other, you've sent me a subscription request but I have not
       responded yet, and I've sent you 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 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 to me, and I've sent you
       a subscription to the contact request but the
   contact does not you have a subscription to the user (i.e., the
   subscription is not responded yet mutual).

   1.  If the contact wants

   9.  "Both" = we're subscribed to cancel the user's subscription, the
       contact MUST send a presence stanza each other (two-way)


8.2 Server Handling of type "unsubscribed" to the
       user:

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

   2.  As Outbound Presence, Categorized by Subscription
    State

   This section defines how a result, the contact's server (1) MUST send a "roster push"
       to all of the contact's available resources that have requested
       the roster, containing handle an updated roster item for the user with
       the 'subscription' attribute set to a value of "none"; (2) MUST
       route the outbound presence
   stanza of type "unsubscribed" to the user,
       first stamping the 'from' address as the bare JID
       (<contact@domain>) of the contact; "subscribe", "subscribed", "unsubscribe", 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@domain'
           subscription='none'
           name='SomeUser'>
         <group>SomeGroup</group>
       </item>
     </query>
   </iq>

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

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

   3.  Upon receiving the presence stanza of type
   "unsubscribed"
       addressed (i.e., route it to the user, the user's server (1) MUST initiate intended recipient and/or make
   a
       "roster push" change 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 subscription state), categorized by the user current
   subscription state. The general rule is offline, the user's that a server MUST modify the
       roster item and send that modified item route the next time
   stanza to the user
       requests intended recipient if it would change the roster); subscription
   state, and (2) SHOULD deliver MUST NOT route the presence stanza
       of type "unsubscribed" to if it would not change the
   subscription state. Detailed definitions are contained in the user:

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

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



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   4.  Upon receiving


   following sections. Naturally, if the presence stanza of type "unavailable"
       addressed to changes the user, subscription
   state, the user's server MUST deliver the
       unavailable presence to the user:

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


7.5.2 Case #2: Cancelling When Subscription 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., change the subscription is mutual).

   1.  If the contact wants to cancel the user's subscription, the
       contact MUST send a presence stanza state.

8.2.1 Subscription State = None

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


8.2.2 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          |
   +-------------------------------------------------------+


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"                   |
   +-------------------------------------------------------+














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8.2.4 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"     |
   +-------------------------------------------------------+


8.2.5 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          |
   +-------------------------------------------------------+


8.2.6 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"                     |
   +-------------------------------------------------------+

















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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"     |
   +-------------------------------------------------------+


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 type "unsubscribed" to the
       user:

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

   2.  As Outbound Presence, Categorized by Presence Type

   This section defines how a result, the contact's server (1) MUST send a "roster push"
       to all of the contact's available resources that have requested
       the roster, containing handle an updated roster item for the user with
       the 'subscription' attribute set to a value of "to"; (2) MUST
       route the outbound presence
   stanza of type "subscribe", "subscribed", "unsubscribe", and
   "unsubscribed" (i.e., route it to the user,
       first stamping the 'from' address as the bare JID
       (<contact@domain>) of the contact; and (3) SHOULD send
       unavailable presence from the contact intended recipient and/or make
   a change to the user: subscription state), categorized by presence type.









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

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

   <presence
       from='contact@domain'
       to='user@domain'
       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 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" (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) SHOULD deliver the presence stanza
       of type "unsubscribed" to the user:

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

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


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 state change         |
   |  "None + Pending Out"    |  no      |  no state change         |
   |  "None + Pending In"     |  yes     |  "From"                  |
   |  "None + Pending Out/In" |  yes     |  "From + Pending Out"    |
   |  "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         |
   +----------------------------------------------------------------+



















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   4.  Upon receiving the


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 a user sends an outbound presence stanza of type "unavailable"
       addressed to the user, the user's server MUST deliver the
       unavailable presence to the user:

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

   Note: Obviously this does not result
   "unsubscribe" that results 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 state change, 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. The process may be
   initiated no matter what the current subscription state is server SHOULD auto-reply by sending a roster set containing an item for the contact with the
   'subscription' attribute set to a value presence stanza of "remove":

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

   When
   type "unsubscribed" to the user removes a contact from his or her roster by setting on behalf of the
   'subscription' attribute contact and MUST
   deliver that presence stanza to a value 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 state change         |
   |  "To + Pending In"       |  yes     |  "To"                    |
   |  "From"                  |  yes     |  "None"                  |
   |  "From + Pending Out"    |  yes     |  "None + Pending Out"    |
   |  "Both"                  |  yes     |  "To"                    |
   +----------------------------------------------------------------+


8.4 Server Handling of "remove", the user's Inbound Presence, Categorized by Subscription
    State

   This section defines how a server
   (1) MUST automatically cancel any existing handle an inbound presence subscription
   between the user
   stanza of type "subscribe", "subscribed", "unsubscribe", and
   "unsubscribed" (i.e., deliver it to the contact (both 'to' and 'from' intended recipient and/or
   make a change to the subscription state), categorized by subscription
   state. (Note: some of the presence stanza type should never be
   received as
   appropriate); (2) inbound stanzas, since the sender's server MUST remove NOT route



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   them to the roster item from intended recipient; however, these stanza types are
   included for the user's roster
   and inform all sake of the user's available resources 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 state change         |
   +--------------------------------------------------------+


8.4.2 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"                  |
   +--------------------------------------------------------+


8.4.3 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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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"     |
   +--------------------------------------------------------+

















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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         |
   +--------------------------------------------------------+


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 the roster item
   removal; (3) Inbound Presence, Categorized by Presence Type

   This section defines how a server MUST inform the resource that initiated the removal handle an inbound presence
   stanza of
   success; type "subscribe", "subscribed", "unsubscribe", and (4) SHOULD send unavailable presence
   "unsubscribed" (i.e., deliver it to the contact: intended recipient and/or
   make a change to the subscription state), categorized by presence
   type.








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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 state change         |
   +------------------------------------------------------------------+


8.5.2 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         |
   +------------------------------------------------------------------+



















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

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

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

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

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

   Upon receiving the


8.5.3 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"                    |
   +------------------------------------------------------------------+


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"                  |
   +------------------------------------------------------------------+


8.6 Server Delivery and Client Acknowledgement of Subscription State
    Change Notifications

   When a server receives an inbound presence stanza of type "subscribe",
   "subscribed", "unsubscribe", the
   contact's server (1) MUST initiate and "unsubscribed" that consists of a "roster push"
   subscription state change notification, in addition to all available
   resources associated with the contact that have requested sending the roster,
   containing an
   appropriate "roster push" (or updated roster item for the user with the
   'subscription' attribute set to a value of "to" (if when the contact roster is
   offline, the contact's server next
   requested), it MUST modify the roster item and send
   that modified item deliver the next time notification to the contact requests intended
   recipient at least once.

   A server MUST require the roster); recipient to approve or deny a subscription
   request (i.e., an inbound presence stanza of type "subscribe") and (2) SHOULD also deliver
   MAY require the unsubscribe command recipient to acknowledge receipt of the contact:

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

   <presence
       to='contact@domain'
       from='user@domain' state change
   notification. In order to require acknowledgement, a server SHOULD



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       type='unsubscribe'/>

   Upon receiving the presence stanza of type "unsubscribed",


   send the
   contact's server (1) MUST initiate a "roster push" notification to all available
   resources associated with the contact that have requested the roster,
   containing an updated roster item for recipient each time the user with recipient logs
   in, until the
   'subscription' attribute set to a value recipient acknowledges receipt of "none" (if the contact is
   offline, notification by
   accepting or denying the contact's server MUST modify relevant notification. Acknowledgement is
   sent by either accepting or denying the roster item and send
   that modified item notification, as shown in the next time
   following table:

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

   Obviously, given the contact requests foregoing subscription state charts, some the roster);
   acknowledgement and (2) SHOULD also deliver the unsubscribe command denial stanzas will be routed to the contact:

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

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

   Upon receiving contact and
   result in subscription state changes, while others will not. However,
   any such stanzas MUST result in the presence stanza of type "unavailable" addressed server's no longer sending the
   subscription state notification to the contact, user.

   Because the contact's sender's server MUST deliver the unavailable automatically generate outbound
   presence to the user:

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

   Note that when the user removes the contact from the user's roster,
   the end state stanzas of the contact's roster is that the user is still in
   the contact's type "unsubscribe" and "unsubscribed" upon
   receiving a roster set with the 'subscription' attribute set to a subscription state
   value of "none"; in order to
   completely remove "remove" (see Section 7.6), the server MUST treat a roster item
   remove request as equivalent to sending those presence stanzas for the user, the contact needs
   purposes of determining whether to
   also send a roster removal request. continue sending subscription
   state change notifications of type "subscribe" or "subscribed" to the
   user.






















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8.


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 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 denying messages based on JID, group, or subscription
      type (or globally).

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

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

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

   o  Allowing or denying 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.

8.1

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 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='nonNegativeInteger'/>
             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@domain/ <user@somedomain/
   resource>, then <user@domain>, <user@somedomain>, then <domain/resource>, <somedomain/resource>, then <domain>.
   <somedomain>. If the value is <user@domain>, <user@somedomain>, then any connected
   resource for that
   user@domain user@somedomain matches. If the value is <domain/resource>,
   <somedomain/resource>, then only that resource matches. If the value
   is <domain>, <somedomain>, then any user@domain user@somedomain (or subdomain) matches.

   If the type is "group", then the 'value' attribute MUST 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 MUST 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].

   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
   one child element (i.e., the stanza must contain only one <active/>



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   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 one
   <item/> child element.

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

8.2

9.2 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 SHOULD be the first routing and delivery rule
       applied by a server, trumping the other rules specified in
       Section 9. 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, 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.  When  If a user updates the definition for a list or adds a new an active list, subsequent
       processing based on that active list
       (whether or not it is active), MUST use the server SHOULD NOT "push" that
       information out to updated
       definition (for all of the user's available resources to which that
       have requested the roster's account, as is done for rosters. If a active list currently
       applies).



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       client or user wants to retrieve the current privacy list
       information, it SHOULD request the relevant list.


   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 and the active session,
       subsequent processing of the based on that active list MUST be based on take into
       account the changed state or group.


8.3 group (for all resources to which
       that active list currently applies).


9.3 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@montague.net/orchard'> 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>
















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   Example: Server sends a privacy list to client:

   <iq type='result' id='getlist2' to='romeo@montague.net/orchard'> to='romeo@example.net/orchard'>
     <query xmlns='jabber:iq:privacy'>
       <list name='public'>
         <item jid='tybalt@capulet.com' type='jid'
               value='tybalt@example.com'
               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@montague.net/orchard'> 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>










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   Example: Server sends yet another privacy list to client:

   <iq type='result' id='getlist4' to='romeo@montague.net/orchard'> to='romeo@example.net/orchard'>
     <query xmlns='jabber:iq:privacy'>
       <list name='special'>
         <item
             type='jid'
             value='juliet@capulet.com'
             value='juliet@example.com'
             action='allow'
             order='6'/>
         <item
             type='jid'
             value='benvolio@shakespeare.lit'
             value='benvolio@example.org'
             action='allow'
             order='7'/>
         <item
             type='jid'
             value='mercutio@verona.it'
             value='mercutio@shakespeare.lit'
             action='allow'
             order='42'/>
         <item action='deny'/> 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>




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   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>


8.4


9.4 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@capulet.com/balcony'/> 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:






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   Example: Client attempts to set a non-existent list as active:

   <iq type='error' id='active2'>
     <query xmlns='jabber:iq:privacy'>
       <list
       <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>
   </iq>


8.5


9.5 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@capulet.com/balcony'/> 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:




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   Example: Client attempts to set a non-existent list as default:

   <iq type='error' id='default2'>
     <query xmlns='jabber:iq:privacy'>
       <list
       <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/>
     </query>
   </iq>


8.6


9.6 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@capulet.com' value='tybalt@example.com'
               action='deny' order='3'/>
         <item type='jid' value='paris@shakespeare.lit' value='paris@example.org'
               action='deny' order='5'/>
         <item action='allow' order='68'/>
       </list>
     </query>
   </iq>



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   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@capulet.com" "tybalt@example.com" item and the
   "paris@shakespeare.lit"
   "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@capulet.com/balcony'/>


8.7 to='juliet@example.com/balcony'/>


9.7 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.

8.8

9.8 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@capulet.com/balcony'/> 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.



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8.9


9.9 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@capulet.com' 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.













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   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>

   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:

   <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.

8.10

9.10 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.








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   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@capulet.com' 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
   will not receive presence notifications from the user with the
   specified JID.

   Example: User blocks based on roster group:

   <iq type='set' id='presin2'>
     <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.



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

   As a result of creating and applying the foregoing list, the user
   will not receive presence notifications from any other users.

8.11

9.11 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 to any given entity.

   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@capulet.com' 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.




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   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>
       </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.




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8.12


9.12 Blocking IQs

   Server-side privacy lists enable a user to block incoming IQ requests
   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.

   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@capulet.com' 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.












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   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/>
         </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.

8.13

9.13 Blocking All Communication

   Server-side privacy lists enable a user to block all communications
   from and presence to 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='all1'>
     <query xmlns='jabber:iq:privacy'>
       <list name='all-jid-example'>
         <item type='jid' value='tybalt@capulet.com' value='tybalt@example.com'
               action='deny' order='23'/>
       </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,
   the user with the specified JID.

   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.








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   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>
     </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.

8.14

9.14 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@montague.net'
       from='tybalt@capulet.com/pda'
       to='romeo@example.net'
       from='tybalt@example.com/pda'
       id='probing1'>
     <query xmlns='jabber:iq:last'/>
   </iq>















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   Example: Server returns error to blocked entity:

   <iq
       type='error'
       from='romeo@montague.net'
       to='tybalt@capulet.com/pda'
       from='romeo@example.net'
       to='tybalt@example.com/pda'
       id='probing1'>
     <query xmlns='jabber:iq:last'/>
     <error type='cancel'>
       <feature-not-implemented
           xmlns='urn:ietf:params:xml:ns:xmpp-stanzas'>
     </error>
   </iq>


8.15


9.15 Higher-Level Heuristics

   When building a representation of a higher-level privacy heuristic, a
   client SHOULD use the simplest possible representation.

   For example, the heuristic "block all communications with any user
   not in my roster" could be constructed in any of the following ways:

   o  accept communications from all JIDs in my roster (i.e., listing
      each JID as a separate list item), but deny communications with
      everyone else

   o  accept 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 deny communications from everyone else

   o  accept communications from any user with whom I have a
      subscription of 'both' or 'to' or 'from' (i.e., listing each
      subscription value separately), but deny communications from
      everyone else

   o  deny 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 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>



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   </iq>


















































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9.


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:

9.1

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 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 of the qualifying
   namespace).

9.2

10.2 Foreign Domain

   If the hostname of the domain identifier portion of the JID contained
   in the 'to' attribute does not match one of the configured hostnames
   of the server itself or a subdomain thereof, the server SHOULD route
   the stanza to the foreign domain (subject to local service
   provisioning and security policies regarding inter-domain
   communication). If routing to the recipient's server is unsuccessful,
   the sender's server MUST return an error to the sender; if the
   recipient's server can be contacted but delivery by the recipient's
   server to the recipient is unsuccessful, the recipient's server MUST
   return an error to the sender by way of the sender's server.

9.3

10.3 Subdomain

   If the hostname of the domain identifier portion of the JID contained
   in the 'to' attribute matches a subdomain of one of the configured
   hostnames of the server itself, the server MAY process the stanza
   itself or MAY route the stanza to a specialized service that is
   responsible for that subdomain (if any).

9.4

10.4 Bare Domain or Specific Resource

   If the hostname of the domain identifier portion of the JID contained



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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 <domain> <somedomain>
   or
   <domain/resource>, <somedomain/resource>, the server (or a defined resource thereof)
   SHOULD process the stanza as appropriate 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, and
   MUST reply with an IQ of type "result" or "error".

9.5

10.5 User in Same Domain

   If the hostname of the domain identifier portion of the JID contained
   in the 'to' attribute matches the hostname of the server itself and
   the JID contained in the 'to' attribute is of the form <user@domain>
   <user@somedomain> or <user@domain/resource>, <user@somedomain/resource>, the server SHOULD
   first apply any privacy rules (Section 8) 9) 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 rules apply:

   1.  If the JID contains a resource identifier (i.e., is of the form
       <user@domain/resource>)
       <user@somedomain/resource>) and there is an available resource
       whose authzid matches the full JID, the recipient's server SHOULD
       deliver the stanza to the session that exactly matches the
       resource identifier.

   2.  If the JID contains a resource identifier 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.  If the JID is of the form <user@domain> <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.

       3.  For IQ stanzas, the server SHOULD deliver the stanza to all
           available resources, except that the server MUST NOT deliver
           the stanza to an available resource that provided a negative
           value for the <priority/> element.

   4.  If the JID is of the form <user@domain> <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.

       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 MUST reply 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 the case with the 'jabber:iq:last'
           protocol defined above); if not, the server MUST reply with a
           <service-unavailable/> stanza error.














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10.


11. IANA Considerations

   For several related IANA considerations, refer to XMPP Core [1].

10.1

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 the Extensible Messaging and Presence Protocol (XMPP) as
      defined by [RFCXXXX].

   Registrant Contact: IETF, XMPP Working Group, <xmppwg@jabber.org>

































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11.


12. Security Considerations

   For security considerations, refer to the relevant section of XMPP
   Core [1].















































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Normative References

   [1]  Saint-Andre, P. and J. Miller, "XMPP Core",
        draft-ietf-xmpp-core-15 (work in progress), June 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.









































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Informative References

   [4]  Jabber Software Foundation, "Jabber Software Foundation", August
        2001, <http://www.jabber.org/>.

   [5]  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>.

   [6]  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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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 [6] is in common use within the
   Jabber community to provide such information. Documentation of this
   protocol is maintained by the Jabber Software Foundation [4] at
   <http://www.jabber.org/protocol/> but is out of scope for this
   document.









































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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 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

   <?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'
       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'?>



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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'
                       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:nonNegativeInteger'
                       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 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>

     <xs:element name='group' type='xs:string'/>

   </xs:schema>




































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Appendix C. 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 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.2 Changes from draft-ietf-xmpp-im-13

   o  Made one small change to privacy list syntax rules.


C.2


C.3 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.


C.3


C.4 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.




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   o  Removed the 'jabber:iq:privacy:error' namespace (not necessary).

   o  Documented message type='normal'.

   o  Made numerous small editorial changes throughout.


C.4


C.5 Changes from draft-ietf-xmpp-im-10

   o  Clarified presence responsibilities for servers and clients.



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   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.5


C.6 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.


C.6


C.7 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.7


C.8 Changes from draft-ietf-xmpp-im-07

   o  Added several error cases for resource authorization and updated
      relevant schema.


C.8





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C.9 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.

   o  Removed note to RFC Editor regarding provisional namespace names.





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C.9


C.10 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.10


C.11 Changes from draft-ietf-xmpp-im-04

   o  Specified sending of unavailable presence after unsubscribe and
      subscription-cancellation actions.

   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.11


C.12 Changes from draft-ietf-xmpp-im-03

   o  Fixed order processing on privacy rules per list discussion.

   o  Made numerous small editorial changes.


C.12





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C.13 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).

   o  Removed non-normative documentation of authentication using
      jabber:iq:auth and of in-band registration using



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      jabber:iq:register, since these are maintained by the Jabber
      Software Foundation and are not part of the XMPP specification.


C.13


C.14 Changes from draft-ietf-xmpp-im-01

   o  Made numerous small editorial changes.


C.14


C.15 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'.

   o  Specified the algorithm for digest passwords.


C.15


C.16 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.




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   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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Intellectual Property Statement

   The IETF takes no position regarding the validity or scope of any
   intellectual property or other rights that might be claimed to
   pertain to the implementation or use of the technology described in
   this document or the extent to which any license under such rights
   might or might not be available; neither does it represent that it
   has made any effort to identify any such rights. Information on the
   IETF's procedures with respect to rights in standards-track and
   standards-related documentation can be found in BCP-11. Copies of
   claims of rights made available for publication and any assurances of
   licenses to be made available, or the result of an attempt made to
   obtain a general license or permission for the use of such
   proprietary rights by implementors or users of this specification can
   be obtained from the IETF Secretariat.

   The IETF invites any interested party to bring to its attention any
   copyrights, patents or patent applications, or other proprietary
   rights which may cover technology that may be required to practice
   this standard. Please address the information to the IETF Executive
   Director.


Full Copyright Statement

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

   This document and translations of it may be copied and furnished to
   others, and derivative works that comment on or otherwise explain it
   or assist in its implementation may be prepared, copied, published
   and distributed, in whole or in part, without restriction of any
   kind, provided that the above copyright notice and this paragraph are
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Acknowledgement

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