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Network Working Group                       Steve Silverberg, Microsoft
INTERNET-DRAFT                                  Steve Mansour, Netscape
Calendaring and Scheduling Working Group            Frank Dawson, Lotus
<ietf-draft-calsch-itip-02.txt>
<ietf-draft-calsch-itip-03.txt             Ross Hopson, ON Technologies
Expires in six months from                             November 21,1997                               March 13, 1998

       iCalendar Transport-Independent Interoperability Protocol
                                 (iTIP)
        Scheduling Events, BusyTime, To-dos and Journal Entries


Status of this Memo
This document is an Internet-Draft. Internet-Drafts are working
documents of the Internet Engineering Task Force (IETF), its areas, and
its working groups. Note that other groups MAY may also distribute working
documents as Internet-Drafts.

Internet-Drafts are draft documents valid for a maximum of six months.
Internet-Drafts MAY may be updated, replaced, or made obsolete by other
documents at any time. It is not appropriate to use Internet-
   Drafts Internet-Drafts as
reference material or to cite them other than as a "working draft" or
"work in progress".

To learn the current status of any Internet-Draft, please check the
   1id-abstracts.txt 1id-
abstracts.txt listing contained in the Internet-Drafts Shadow
Directories on ds.internic.net (US East Coast), nic.nordu.net (Europe),
ftp.isi.edu (US West Coast), or munnari.oz.au (Pacific Rim).

Distribution of this document is unlimited.

Copyright (C) The Internet Society 1997. All Rights Reserved.


Abstract
This document specifies how calendaring systems use iCalendar objects to
interoperate with other calendar systems. It does so in a general way so
as to allow multiple methods of communication between systems.
Subsequent documents specify interoperable methods of communications
between systems that use this protocol.

The document outlines a model for calendar exchange that defines both
static and dynamic event, to-do, journal and free/busy objects. Static
objects are used to transmit information from one entity to another
without the expectation of continuity or referential integrity with the
original item. Dynamic objects are a superset of static objects and will
gracefully degrade to their static counterparts for clients that only
support static objects.












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Table of Contents


1    8
Introduction   9 INTRODUCTION.........................................................9

 1.1 Formatting Conventions   9 FORMATTING CONVENTIONS ...........................................9
 1.2 Related Documents   10 RELATED DOCUMENTS ...............................................10
 1.3 Calendar Roles 10
 1.4 iTIP Transactions   11 ITIP ROLES AND TRANSACTIONS .....................................10

2 Interoperability Models     12 INTEROPERABILITY MODELS.............................................11

 2.1 Application Protocol     12 APPLICATION PROTOCOL ............................................12
   2.1.1 Calendar Entry State  13 ........................................12
   2.1.2 Delegation ..................................................13
   2.1.3 Acting on Behalf of other Calendar Users ....................13

3 Application Protocol Elements    13 APPLICATION PROTOCOL ELEMENTS.......................................13

 3.1 Methods For "VEVENT" Calendar Component 15
  3.1.1 COMMON COMPONENT RESTRICTION TABLES .............................14
 3.2 METHODS FOR VEVENT CALENDAR COMPONENTS ..........................15
   3.2.1 PUBLISH     15
  3.1.2 REQUEST     16
    3.1.2.1 .....................................................16
   3.2.2 REQUEST for .....................................................17
     3.2.2.1 Rescheduling an Event     18
    3.1.2.2 REQUEST for Update Event....................................18
     3.2.2.2 Updating or Reconfirmation of an Event     18
    3.1.2.3 REQUEST for Event...................19
     3.2.2.3 Delegating an Event from an "Attendee" to
    another CU 18
    3.1.2.4 REQUEST for Delegating role of "Organizer" to another CU  19
    3.1.2.5 REQUEST for CU........................19
     3.2.2.4 Changing the "Organizer" from one CU to another
     19
    3.1.2.6 REQUEST for Changing Organizer...................................20
     3.2.2.5 Sending on Behalf of the "Owner" 19
    3.1.2.7 REQUEST Forwarded To Organizer.......................20
     3.2.2.6 Forwarding to An Uninvited Calendar User 20
    3.1.2.8 REQUEST Updated CU............................20
     3.2.2.7 Updating Attendee Status  20
  3.1.3 Status.................................20
   3.2.3 REPLY  20
  3.1.4 .......................................................20
   3.2.4 ADD .........................................................22
   3.2.5 CANCEL 21
  3.1.5 ......................................................23
   3.2.6 REFRESH     22
  3.1.6 .....................................................25
   3.2.7 COUNTER     23
  3.1.7 .....................................................26
   3.2.8 DECLINECOUNTER   24
 3.2 Methods For ..............................................28
 3.3 METHODS FOR VFREEBUSY Component    25
  3.2.1 COMPONENTS ................................29
   3.3.1 PUBLISH     26
  3.2.2 .....................................................30
   3.3.2 REQUEST     27
  3.2.3 .....................................................31
   3.3.3 REPLY  28
 3.3 Methods For .......................................................32
 3.4 METHODS FOR VTODO Component   29
  3.3.1 COMPONENTS ....................................34
   3.4.1 PUBLISH     30
  3.3.2 .....................................................35
   3.4.2 REQUEST     31
    3.3.2.1 .....................................................36
     3.4.2.1 REQUEST for Rescheduling a VTODO 32
    3.3.2.2 VTODO.........................37
     3.4.2.2 REQUEST for Update or Reconfirmation of a VTODO 33
    3.3.2.3 VTODO..........38
     3.4.2.3 REQUEST for Delegating a VTODO   33
    3.3.2.4 VTODO...........................38
     3.4.2.4 REQUEST Forwarded To An Uninvited Calendar User 34
    3.3.2.5 User..........39
     3.4.2.5 REQUEST Updated Attendee Status  34
  3.3.3 Status..........................39
   3.4.3 REPLY  35
  3.3.4 .......................................................39
   3.4.4 ADD .........................................................41
   3.4.5 CANCEL 36
  3.3.5 ......................................................42
   3.4.6 REFRESH     37
  3.3.6 .....................................................43
   3.4.7 COUNTER     37
  3.3.7 .....................................................45
   3.4.8 DECLINECOUNTER   38
 3.4 Methods For VJOURNAL Component     39
  3.4.1 PUBLISH     40
  3.4.2 CANCEL 41
  3.4.3 REFRESH     41 ..............................................46
 3.5 Status Replies 42 METHODS FOR VJOURNAL COMPONENTS .................................47


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   3.5.1 PUBLISH .....................................................47
   3.5.2 ADD .........................................................49
   3.5.3 CANCEL ......................................................50
 3.6 Implementation Considerations 44
  3.6.1 STATUS REPLIES ..................................................51
 3.7 IMPLEMENTATION CONSIDERATIONS ...................................53
   3.7.1 Working With Recurrence Instances    44
  3.6.2 ...........................53
   3.7.2 Attendee Property Considerations     45
  3.6.3 When To Refresh An Event   46
  3.6.4 Timezones   46
  3.6.5 Alarms 46
  3.6.6 SUMMARY Property 46
  3.6.7 ............................54
   3.7.3 X-Tokens    47 ....................................................55

4 Examples     47 EXAMPLES............................................................55

 4.1 Published Event Examples 47 PUBLISHED EVENT EXAMPLES ........................................55
   4.1.1 A Minimal Published Event  47 ...................................56
   4.1.2 Changing A Published Event 48 ..................................56
   4.1.3 Canceling A Published Event     49 .................................57
   4.1.4 A Rich Published Event     49 ......................................57
   4.1.5 Anniversaries or Events attached to entire days     51 .............58
 4.2 Group Event Examples     51 GROUP EVENT EXAMPLES ............................................59
   4.2.1 A Group Event Request 52 .......................................60
   4.2.2 Reply To A Group Event Request  52 ..............................60
   4.2.3 Update An Event  53 .............................................61
   4.2.4 Countering an Event Proposal    53 ................................61
   4.2.5 Delegate An Delegating an Event     55 .........................................63
   4.2.6 Delegate Accepts the Meeting    58 ................................65
   4.2.7 Delegate Declines the Meeting   58 ...............................66
   4.2.8 Forwarding an Event Request     59 .................................67
   4.2.9 Cancel A Group Event  59
 4.3 Busy Time Examples  60 ........................................67
   4.2.10 Removing Attendees .........................................68
   4.2.11 Replacing the Organizer ....................................69
 4.3 BUSY TIME EXAMPLES ..............................................70
   4.3.1 Request Busy Time     60 ...........................................70
   4.3.2 Reply To A Busy Time Request    61 ................................71
 4.4 Recurring Event and Time Zone Examples  61 RECURRING EVENT AND TIME ZONE EXAMPLES ..........................71
   4.4.1 A Recurring Event Spanning Time Zones     61 .......................71
   4.4.2 Modify A Recurring Instance     63 .................................73
   4.4.3 Cancel A Recurring an Instance     64 ..........................................74
   4.4.4 Cancel An Exception   65
  4.4.5 Cancel Recurring Event     65
  4.4.6 ......................................75
   4.4.5 Change All Future Instances     65
  4.4.7 .................................75
   4.4.6 Add A New Instance To A Recurring Event   66 .....................75
   4.4.7 Add A New Series of Instances To A Recurring Event ..........76
   4.4.8 Counter An Instance Of A Recurring Event  67 ....................80
   4.4.9 Error Reply To A request   67 Request ....................................80
 4.5 Group To-do Examples     68 GROUP TO-DO EXAMPLES ............................................81
   4.5.1 A VTODO Request  69 .............................................82
   4.5.2 A VTODO Reply    70 ...............................................83
   4.5.3 A VTODO Refresh  70 Request for Updated Status ..........................83
   4.5.4 A Refresh Reply: Percent-Complete    71 ...................................84
   4.5.5 A Refresh Reply: Completed 71 ..........................................84
   4.5.6 An Updated VTODO Request   71 ....................................84
   4.5.7 A Recurring VTODOs    72 ............................................85
     4.5.7.1 Request for a Recurring VTODO    72 VTODO............................85
     4.5.7.2 Calculating due dates in recurring VTODOs  72 VTODOs................85
     4.5.7.3 Replying to an instance of a recurring VTODO    73 VTODO.............86
 4.6 Journal Examples    73 JOURNAL EXAMPLES ................................................86


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 4.7 Other Examples 74 OTHER EXAMPLES ..................................................87
   4.7.1 Event Refresh    74 ...............................................87
   4.7.2 Bad RECURRENCE-ID     74
5 Application Protocol Fallbacks   75


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 5.1 Partial Implementation   75 PARTIAL IMPLEMENTATION ..........................................88
   5.1.1 Event-Related Fallbacks    76 .....................................89
   5.1.2 To-Do-Related Fallbacks    77 .....................................90
   5.1.3 Journal-Related Fallbacks  79 ...................................92
 5.2 Latency Issues 80 LATENCY ISSUES ..................................................93
   5.2.1 Cancellation of an Unknown Calendar Component. 80 ..............93
   5.2.2 Unexpected Reply from an Unknown Delegate 80 ...................93
 5.3 Sequence Number     81 SEQUENCE NUMBER .................................................94

6 Security Considerations     81 SECURITY CONSIDERATIONS.............................................94

 6.1 Security Threats    81 SECURITY THREATS ................................................94
   6.1.1 Spoofing the "Organizer"   81 ....................................94
   6.1.2 Spoofing the "Attendee"    82 .....................................94
   6.1.3 Eavesdropping    82 Unauthorized Replacement of the Organizer ...................95
   6.1.4 Eavesdropping ...............................................95
   6.1.5 Flooding a Calendar   82
  6.1.5 .........................................95
   6.1.6 Procedural Alarms     82 ...........................................95
   6.1.7 Unauthorized REFRESH Requests ...............................95
 6.2 Recommendations     82 RECOMMENDATIONS .................................................95
   6.2.1 Use of [RFC1847] to secure iTIP transactions   82 ................96
   6.2.2 Implementation Controls    83 .....................................96

7 Acknowledgments   83 ACKNOWLEDGMENTS.....................................................96


8 Bibliography 83 BIBLIOGRAPHY........................................................97


9 Authors Addresses 84 AUTHORS ADDRESSES...................................................98


10 Full Copyright Statement   85


1 FULL COPYRIGHT STATEMENT...........................................99

















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1  Introduction

This document specifies how calendaring systems use iCalendar objects to
interoperate with other calendar systems. In particular, it specifies
how to schedule events, to-dos, or daily journal entries. It further
specifies how to search for available busy time information. It does so
in a general way so as to allow multiple methods of communication
between systems. Subsequent documents specify interoperable methods of communications transport bindings between
systems that use this protocol.

This protocol is based on requests messages sent from an originator and
   conveyed to one or
more recipients. A recipient For certain types of messages, a request MAY recipient may reply,
in order to update their status and MAY may also return transaction/request
status information. The protocol also supports the ability for the entry message
originator to modify or cancel the original
   entry. message. The protocol also
supports the ability for recipients to suggest changes to the originator
of a message. The elements of the protocol also include define the notion of user
   roles. roles
for its transactions.


1.1 Formatting Conventions

In order to refer to elements of the calendaring and scheduling model,
core object or interoperability protocol defined in [ICMS], [ICAL] and
[ITIP] several formatting conventions have been utilized.

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

Calendaring and scheduling roles defined described by [ICMS] are referred to in
quoted-strings of text with the first character of each word in upper
case. For example, "Organizer" refers to a role of a "Calendar User"
(CU) within the scheduling protocol defined by [ITIP] [ITIP]. Calendar
components defined by [ICAL] are referred to with capitalized, quoted-strings quoted-
strings of text. All calendar components start with the letter "V". For
example, "VEVENT" refers to the event calendar component, "VTODO" refers
to the to-do calendar component and "VJOURNAL" refers to the daily
journal calendar component. Scheduling methods defined by [ITIP] are
referred to with capitalized, quoted-strings of text. For example,
"REQUEST" refers to the method for requesting a scheduling calendar
component be created or modified, "REPLY" refers to the method a
recipient of a request uses to update their status with the "Organizer"
of the calendar component.

Properties defined by [ICAL] are referred to with capitalized,
   quoted-strings quoted-
strings of text, followed by the word "property". For example,
"ATTENDEE" property refers to the iCalendar property used to convey the
calendar address of a "Calendar User". Property parameters defined by
this memo are referred to with lower case, quoted-strings of text,
followed by the word "parameter". For example, "value" parameter refers
to the iCalendar property parameter used to override the default data


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type for a property value. Enumerated values defined



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referred to with capitalized text, either alone or followed by the word
"value".

In tables, the quoted-string text is specified without quotes in order
to minimize the table length.


1.2 Related Documents

Implementers will need to be familiar with several other memos that,
along with this one, describe the Internet calendaring and scheduling
standards. This document, [ITIP], specifies an interoperability protocol
for scheduling between different implementations; implementations. The related documents
are:

     [ICMS] - describes the abstract model and defines common terms and
     concepts;

     [ICAL] - specifies the objects, data types, properties and property
     parameters used in the protocols, along with the methods for
     representing and encoding them;

     [IRIP] - specifies an Internet real time protocol binding for
     [ITIP].
     [ITIP];

     [IMIP] specifies an Internet email binding for [ITIP].

This memo does not attempt to repeat the specification of concepts or
definitions from these other memos. Where possible, references are made
to the memo that provides for the specification of these concepts or
definitions.


1.3 Calendar Roles ITIP Roles are a behavior or set of activities performed by particular
   groups of users or agents at a given state of and Transactions

ITIP defines seven methods for exchanging [ICAL] objects for the calendar
   transaction. This specification describes 4
purposes of group calendaring and scheduling between "Calendar Users"
(CUs). CUs take on one of two roles that determine in iTIP. The CU who initiates an
exchange takes on the role of "Organizer". For example, the CU who
proposes a
   range group meeting is the "Organizer". The CUs asked to
participate in the group meeting by the "Organizer" take on the role of actions
"Attendee". Note that  "role" is also a descriptive parameter to the
_ATTENDEE_ property. Its use is to convey descriptive context to an
"Attendee" such as "chair", "req-participant" or "non-participant" and responsibilities specific
has nothing to each role.

+=====================================================================+ do with the calendaring workflow.

The ITIP methods are defined below and their usage and semantics are
outlined in section 3 of this document.

+================+==================================================+
|  Role Name Method         |  Description                                     |
|=====================================================================|
|================+==================================================|
| Owner PUBLISH        | The Used to publish a calendar entry owner is the only to one or more  |


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|                | Calendar User Users. There is no interactivity        |
|                | allowed to directly modify an entry using between the iTIP publisher and any other calendar     |
|                | protocol. However, the Owner MAY delegate or user. An example might include a baseball team   |
|                | assign an Organizer publishing its schedule to manage the entry on their public.           |
|                | behalf. Usually, a calendar entry Owner is also the                                                  |
| REQUEST        | Organizer. Used to schedule a calendar entry with other     |
|                | Calendar Users. Requests are interactive in that |
| Organizer                | The Organizer controls manipulation of they require the calendar receiver to respond using       |
|                | entry. In most cases, the Owner and the Organizer Reply methods. Meeting Requests, Busy    |
|                | are Time requests and the same Calendar User. assignment of VTODOs to    |
|                | other Calendar Users are all examples.           |
| Attendee                | An Attendee is a Calendar User associated with Requests are also used by the "Organizer" to     |


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|                | update the status of a calendar entry via a Request method issued by an entry.           |
|                | Organizer or another Attendee. Attendees are not                                                  |
| REPLY          | capable of directly manipulating calendar entries, A Reply is used in response to a Request to      |
|                | but MUST act through convey "Attendee" status to the Organizer.                  |
|              | "Organizer".     |
| Delegate                | A Delegate is a proxy that acts on behalf of another Replies are commonly used to respond to meeting  |
|                | Calendar User. ITIP addresses two forms of and task requests.                               |
|                | delegation:                                                  |
| ADD            | 1) An Owner MAY delegate Add one or re-assign more instances to an Organizer   | existing         |
| to manage a calendar entry                | VEVENT, VTODO, or VJOURNAL.                      |
| 2) An Attendee MAY delegate a calendar entry request                |                                                  |
| to another Calendar User. CANCEL         |
+=====================================================================+


1.4 iTIP Transactions


   This protocol defines seven methods for exchanging [ICAL] objects for
   the purposes of group calendaring and scheduling between "Calendar
   Users". The methods are defined below and their usage and semantics
   are outlined in section 3 Cancel one or more instances of this document.

+================+==================================================+ an existing      | Method
|  Description                |
|================+==================================================| VEVENT, VTODO, or VJOURNAL.                      | PUBLISH
| Used to publish a calendar entry to one or more                |                                                  |
| Calendar Users. There REFRESH        | The Refresh method is no interactivity used by an "Attendee" to   |
|                | between request the publisher and any other latest version of a calendar entry.  |
|                | user. An example might include a baseball team                                                  |
| COUNTER        | publishing its schedule The Counter method is used by an "Attendee" to the public.   |
|                | negotiate a change in the calendar entry.        |
| REQUEST                | Used Examples include the request to schedule change a calendar entry with other         |
|                | Calendar Users. Requests are interactive in that |
|                | they MAY require the receiver to respond using   |
|                | the the Reply methods. Meeting Requests, Busy    |
|                | Time requests and the assignment of VTODOs to    |
|                | other Calendar Users are all examples.           |
|                | Requests are also used by the "Organizer" to     |
|                | update the status of a calendar entry.           |
| REPLY          | A Reply is used in response to a Request to      |
|                | convey "Attendee" status to the "Organizer".     |
|                | Replies are commonly used to respond to meeting  |
|                | and task requests.                               |
|                |                                                  |
| CANCEL         | The Cancel method is used to cancel an existing  |
|                | calendar entry such as a VEVENT or VTODO.        |
|                |                                                  |
| REFRESH        | The Refresh method is used by an "Attendee" to   |
|                | request the latest version of a calendar entry   |
|                |                                                  |
| COUNTER        | The Counter method is used by an "Attendee" to   |
|                | negotiate a change in the calendar entry.        |
|                | Examples include the request to change a         |


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|                | proposed Event time or change the due date for a |
|                | VTODO.                                           |
| DECLINE-                |                                                  |
| COUNTER DECLINE-       | Used by the "Organizer" to decline the proposed  |
| COUNTER        | counter-proprosal by an "Attendee" counter-proprosal.                               |
+================+==================================================+


2  Interoperability Models

There are two distinct protocols relevant to interoperability: an
"Application Protocol" and a "Transport Protocol". The Application
Protocol defines the content of the iCalendar objects sent between
sender and receiver to accomplish the scheduling transactions listed
   in section 1.4. described
above. The Transport Protocol defines how the iCalendar objects are sent
between the sender and receiver. This document focuses on the
Application Protocol. Binding documents such as [IMIP] and [IRIP] focus
on the Transport Protocol.

The connection between Sender and Receiver in the diagram below refers
to the Application Protocol. In particular, the The iCalendar objects passed from the
Sender to the Receiver which conform to those are presented in Section 3, Application Protocol
Elements.


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+----------+                      +----------+
|          |        iTIP          |          |
|  Sender  |<-------------------->| Receiver |
|          |                      |          |
+----------+                      +----------+

There are several variations of this diagram in which the Sender and
Receiver take on various roles of "CUA" a "Calendar User Agent" (CUA) or CS. These a
"Calendar Service" (CS). These variants are detailed in the Model
document [ICMS] [ICMS].

The architecture of iTIP is depicted in the diagram below. An
application written to this specification MAY may work with bindings for the
store-and-forward transport, the real time transport, or both. Also note
that iTIP could be bound to other transports. If a
   capability is not available on a particular transport binding, iTIP
   provides a mechanism for indicating so.

+------------------------------------------+
|                   iTIP                   |
+------------------------------------------+
|Real-time | Store-and-Fwd | Other         |
|Transport | Transport     | Transports... |
+------------------------------------------+


2.1 Application Protocol

The iTIP model for the application protocol is centered with the
   "Organizer" of the calendar entry. That is, the "Organizer" of in which a


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   Calendar calendar entry sends a request to one or more "Attendees". The
   "Attendees" then reply to the is created and managed by an
"Organizer". The "Organizer" maintains
   the status interacts with other CUs by sending one or
more of the event.

   The "Owner" is usually iTIP messages described above. "Attendees" use the "Organizer" of "REPLY"
method to communicate their status. "Attendees" do not make direct
changes to the master calendar entry.
   However, They can, however, use the "Owner" MAY delegate or assign an "Organizer"
"COUNTER" method to manage
   the calendar entry on their behalf. In cases where the "Owner" has
   delegated suggest changes to another "Organizer", the "Owner" must still be specified
   in associated "REQUEST" and "COUNTER" methods. "Organizer". The data sources for the application protocol are the "Calendar
   Users". Examples of these users are the "Organizer" and "Attendees"
   of an iCalendar event. The data objects are
has complete control over the iCalendar objects
   that are exchanged between "Calendar Users". master calendar entry.


2.1.1     Calendar Entry State

There are two distinct states relevant to calendar entries: the overall
state of the entry and the state associated with an "Attendee" to that
entry.

The state of an entry is defined by the "STATUS" property and is
controlled by the "Organizer." There is no default value for the
"STATUS" property. The "Organizer" MAY either set sets the "STATUS" property to TENTATIVE or CONFIRMED values. The "Organizer" MAY also
   set the "STATUS" property to CANCELLED
appropriate value by sending a "CANCEL"
   method to for each "Attendee". calendar entry.

The state of a particular "Attendee" relative to an entry is defined by
the "STATUS" property "attstat" parameter in the "ATTENDEE" property for
   that each "Attendee".
When an "Organizer" sends out an entry, issues the state
   associated with each initial entry, "Attendee" status is NEEDS-ACTION.
unknown. The "Organizer" specifies this by setting the "attstat"
parameter to "needs-action". Each "Attendee" MAY
   modify modifies their "ATTENDEE"
property "STATUS" "attstat" parameter to an appropriate value and send it as part of a
"REPLY" message sent back to the "Organizer" in a "REPLY" message.

3 Application Protocol Elements

   Messages are "Organizer".



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2.1.2     Delegation

Delegation is defined as the process by which an "Attendee" grants
another CU (or several CUs) the right to attend on their behalf. The
"Organizer" is made aware of this change because the delegating
"Attendee" informs the "Organizer" of this change. These steps are
detailed in the REQUEST method section.

2.1.3     Acting on Behalf of other Calendar Users

In many organizations one user will act on behalf of another to organize
and/or respond to meeting requests. ITIP provides two mechanisms that
support these activities.

First, the "Organizer" is treated as a special entity, separate from
"Attendees". All responses from "Attendees" flow to the "Organizer",
making it easy to separate a calendar user organizing a meeting from
calendar users attending the meeting. Additionally, iCalendar provides
descriptive roles for each "Attendee". For instance, a role of "chair"
may be ascribed to one or more "Attendees". The "chair and the
"Organizer" may or may not be the same calendar user. This maps well to
scenarios where an assistant may manage meeting logistics for another
individual who chairs a one-time or recurring meeting.

Second, a "sent-by" parameter may be specified in either the "Organizer"
or "Attendee" properties. When specified, the "sent-by" parameter
indicates that the responding CU acted on behalf of the specified
"Attendee" or "Organizer".

3 Application Protocol Elements

ITIP messages are "text/calendar" MIME entities that contain calendaring
and scheduling information. The particular type of [ICAL] message is
referred to as the "method type". Each method type is identified by a
"METHOD" property specified as part of the "text/calendar" content type.
The table below shows various combinations of calendar components and
the method types that this memo supports.


+=================================================+
|         | VEVENT | VTODO | VJOURNAL | VFREEBUSY |
|=================================================|
|Publish  |  Yes   |  Yes  |  Yes     |   Yes     |
|Request  |  Yes   |  Yes  |  No      |   Yes     |
|Refresh  |  Yes   |  Yes  |  Yes  No      |   No      |
|Cancel   |  Yes   |  Yes  |  Yes     |   No      |
|Add      |  Yes   |  Yes  |  Yes     |   No      |
|Reply    |  Yes   |  Yes  |  No      |   Yes     |
|Counter  |  Yes   |  Yes  |  No      |   No      |


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|Decline- |        |       |          |           |
|Counter  |  Yes   |  Yes  |  No      |   No      |
+=================================================+




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Each method type is defined in terms of its associated components and
properties. Some components and properties are required, some are
optional and others are excluded. The property restrictions are expressed in this memo
document using a simple "restriction table". The first column indicates
the following formal notation:

     prop-restriction    = "(" description component method
               1*MUST-component *MAY-component *not-component ")"

     description    = "DESCRIPTION" *ws text name of a component      = "COMPONENT" *ws ("CALPROPOS" / "VEVENT" /
                      "VTODO" / "VJOURNAL")
     method         = "METHOD" *ws <any or property. Properties of the methods defined in this
                       memo for the associated calendar component>

     MUST-component = "MUST COMPONENT =" *ws ("VEVENT" / "VTODO" /
                      "VJOURNAL" / "VTIMEZONE" / "VALARM" /
                      "VFREEBUSY" / "X-TOKEN")
                      *ws "(" [ws] 1*MUST-props *ws
                      *MAY-props *ws *not-props *ws ")"

     MAY-component  = "MAY COMPONENT =" *ws ("VEVENT" / "VTODO" /
                      "VJOURNAL" / "VTIMEZONE" / "VALARM" /
                      "VFREEBUSY" / "X-TOKEN")
                      *ws "(" [ws] ((*MUST-props *ws
                      *MAY-props *ws *not-props *ws) / any) ")"

     not-component  = "NOT COMPONENT =" *ws ("VEVENT" / "VTODO" /
                      "VJOURNAL" / "VTIMEZONE" / "VALARM" /
                      "VFREEBUSY" /"X-TOKEN")

     MUST-props     = "MUST PROPERTY =" *ws restriction-list
     MAY-props      = "MAY PROPERTY =" *ws (restriction-list / any)
     not-props      = "NOT PROPERTY =" *ws (restriction-list)

     restriction-list    = restriction
                         / restriction *ws "," *ws restriction
     restriction    = property-name
                      [*ws "{" parm-or-val-restriction "}"]
     property-name  = <any of the valid properties for the component>
     parm-or-val-restriction  = <a text string description iCalendar object
are not indented. Properties of a
                    constraint on component are indented. The second
column contains "MUST" if the component or property parameters must be present,
"MAY" if the component or property is optional, and "NOT" if the
component or values> property must not be present. Entries in the second column
sometimes contain comments for further clarification.


3.1 Common Component Restriction Tables

DateTime values MAY refer to a "VTIMEZONE" component. The property
restrictions in the table below apply to any       = "ANY"  -- Specifies that "VTIMEZONE" component in an
ITIP message.

Component/Property  Presence
------------------- ----------------------------------------------
VTIMEZONE           MUST be present if any permissible
                 properties are allowed - -

     ws        = HTAB / SPACE

     HTAB      = <Horizontal TAB character>
     SPACE     = <Required Space character> date/time refers to a
                        timezone
    LAST-MODIFIED   MAY
    TZID            MUST
    TZURL           MAY
    STANDARD        MUST
       DTSTART      MUST be present if RRULE is present
       TZOFFSETFROM MUST
       TZOFFSETTO   MUST
       COMMENT      MAY
       RDATE        MAY be present, if present RRULE must not be
                        present
       RRULE        MAY be present, if present RDATE must not be
                        present
       TZNAME       MAY
    DAYLIGHT        MAY
      DTSTART       MUST
      TZOFFSET      MUST
      COMMENT       MAY
      RDATE         MAY be present, if present RRULE must not be
                        present
      RRULE         MAY be present, if present RDATE must not be
                        present
      TZNAME        MAY


The property restrictions in the table below apply to any "VALARM"
component in an ITIP message.

Component/Property  Presence
------------------- ----------------------------------------------
VALARM              MAY
    ALARM-TYPE      MUST
    DURATION        MUST


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    REPEAT          MUST
    TRIGGER         MUST
    ATTACH          MAY
    DESCRIPTION     MAY
    SUMMARY         MAY
    COMMENT         NOT
    CREATED         NOT
    LAST-MODIFIED   NOT
    RELATED-TO      NOT
    URL             NOT



3.2 Methods For "VEVENT" for VEVENT Calendar Component Components

This section defines the property set restrictions for the method types
that are applicable to the "VEVENT" calendar component. Each of
   the methods method is
defined using a grammar table that clarifies the property constraints that
define the particular method.

The following summarizes the methods that are defined for the "VEVENT"
calendar component.

+================+==================================================+
| Method         |  Description                                     |
|================+==================================================|
| PUBLISH        | Post notification of an event. Used primarily as |
|                | a method of advertising the existence of an      |
|                | event.                                           |
|                |                                                  |
| REQUEST        | Make a request for an event. This is an explicit |
|                | invitation to one or more "Attendees". Event     |
|                | Requests are also used to update or change an    |
|                | existing event. Clients that cannot handle       |
|                | REQUEST MAYdegrade may degrade the event to view it as an   |
|                | PUBLISH.                                         |
|                |                                                  |
| REPLY          | Reply to an event request. Clients MAYset may set their |
|                | status ("attstat") to ACCEPTED, DECLINED,        |
|                | ACCEPTED, DECLINED, TENTATIVE, or DELEGATED.                         |
| CANCEL                | Cancel an                                                  |
| ADD            | Add one or more instances to an existing event request. event.  |
|                |                                                  |
| CANCEL         | Cancel one or more instances of an existing      |
|                | event.                                           |
|                |                                                  |
| REFRESH        | A request is sent to an "Organizer" by an "Attendee"        |
|                | "Organizer" "Attendee" asking                               |
   |                | for the latest version of an   |
|                | event to be resent  |
   |                | to the requester.             |
|                |                                                  |
| COUNTER        | Counter a REQUEST with an alternative proposal. proposal,  |
|                | Sent by an "Attendee" to the "Organizer".        |
|                |                                                  |
| DECLINECOUNTER | Decline a counter proposal by proposal. Sent to an "Attendee".           |


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|                | "Attendee" by the "Organizer".                   |
+================+==================================================+


3.1.1


3.2.1     PUBLISH

The "PUBLISH" method in a "VEVENT" calendar component provides is an unsolicited
posting of an iCalendar object. Any "Calendar User" MAY CU may add the published components to
their calendar. It requires and
   accepts The "Organizer" MUST be present in a published iCalendar
component. Other "Attendees" MAY be present. However, no responses to the "Organizer". replies are
expected. Its expected usage is for encapsulating an arbitrary event or to-do as
an iCalendar object. The "Organizer" MAY may subsequently update (with
another "PUBLISH" method) method), add instances to (with an "ADD" method), or
cancel (with a "CANCEL" method) a previously published "VEVENT" calendar
component.

This method type is an iCalendar object that conforms to the following
property constraints:

     (DESCRIPTION "Event - Publish" COMPONENT "VEVENT" METHOD "PUBLISH


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Component/Property  Presence
------------------- ----------------------------------------------
PRODID              MUST COMPONENT = CALPROPS (
          MUST PROPERTY = PRODID, VERSION{"2.0"}, METHOD{"PUBLISH"})
VERSION             MUST COMPONENT = be "2.0"
METHOD              MUST be "PUBLISH"
VEVENT (              MUST PROPERTY = ATTENDEE{ROLE=OWNER and
     DTSTAMP        MUST
     DTSTART        MUST
     ORGANIZER      MUST
     RECURRENCE-ID  MUST only if referring to an instance of a
                        recurring calendar component.  Otherwise it
                        must NOT be present.
     SEQUENCE       MUST be present if not 0, may be present if
               different}, DESCRIPTION{MAY BE NULL},DTSTAMP, DTSTART,
               SEQUENCE{IF NE 0}, 0
     SUMMARY        MUST; may be null.
     UID            MUST

     ATTENDEE       MAY PROPERTY = ATTACH, ATTENDEE{other than ROLE=OWNER |
               ORGANIZER}, CATEGORIES, CLASS, COMMENT,
               CREATED, DTEND, EXDATE, EXRULE, GEO, LAST-MODIFIED,
               LOCATION,PRIORITY, RELATED-TO, RDATE, RECURRENCE-ID,
               RESOURCES, RRULE, SEQUENCE{IF EQ 0},
               STATUS{TENTATIVE/CONFIRMED/CANCELLED},
               SUMMARY{MAYBE NULL}, URL
          NOT PROPERTY = REQUEST-STATUS, TRANSP)
     ATTACH         MAY COMPONENT = VTIMEZONE (
          MUST PROPERTY = DTSTART, TZOFFSET
     CATEGORIES     MAY PROPERTY = COMMENT, DAYLIGHT, (RDATE / RRULE), TZNAME,
          NOT PROPERTY = CREATED)
     CLASS          MAY COMPONENT = VALARM (
          MUST PROPERTY = CATEGORIES, DSTART, DURATION, REPEAT
     COMMENT        MAY PROPERTY = ATTACH, DESCRIPTION, SUMMARY
          NOT PROPERTY = COMMENT, CREATED, LAST-MODIFIED, RELATED-TO,
               URL)
     CONTACT        MAY COMPONENT = X-TOKENS (ANY)
     NOT COMPONENT = VTODO
     NOT COMPONENT = VJOURNAL
     NOT COMPONENT = VFREEBUSY
     )

3.1.2     REQUEST


   The "REQUEST" method in a "VEVENT" calendar component provides the
   following scheduling functions:

      . Invite "Attendees" to an event;

      . Reschedule an existing event;

      . Update the details of an existing event, without rescheduling
        it;

      . Update
     CREATED        MAY
     DESCRIPTION    MAY be present and MAY be NULL
     DTEND          MAY
     EXDATE         MAY
     EXRULE         MAY
     GEO            MAY
     LAST-MODIFIED  MAY
     LOCATION       MAY
     PRIORITY       MAY
     RELATED-TO     MAY
     RDATE          MAY
     RESOURCES      MAY
     RRULE          MAY


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     STATUS         MAY be one of TENTATIVE/CONFIRMED/CANCELLED
     TRANSP         MAY
     URL            MAY

     DURATION       NOT

VTODO               NOT
VJOURNAL            NOT

VTIMEZONE           MUST be present if any date/time refers to a
                        timezone
VALARM              MAY
VFREEBUSY           NOT
X-TOKENS            MAY


3.2.2     REQUEST

The "REQUEST" method in a "VEVENT" component provides the following
scheduling functions:

. Invite "Attendees" to an event;
. Reschedule an existing event;
. Update the details of an existing event, without rescheduling it;
. Update the status of "Attendees" of an existing event, without
  rescheduling it;
. Reconfirm an existing event, without rescheduling it;
. To forward a VEVENT to another uninvited CU.
. For an existing "VEVENT" calendar component, delegate the role of
  "Attendee" to another "Calendar User"; CU;
. For an existing "VEVENT" calendar component, delegate changing the role of
  "Organizer" to another "Calendar User".



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The originator of the "REQUEST" method is the "Organizer" of the
   event. Normally this is the "Owner" of originates the event. "REQUEST". The recipient recipients of the
"REQUEST" method is are the "Calendar User" CUs invited to the event,
   called the "Attendee". The "Attendee" uses "Attendees".
"Attendees" use the "REPLY" method to convey their attendance status to the "Organizer" of a VEVENT
   "REQUEST".
"Organizer".

The "UID" and "SEQUENCE" properties are used to distinguish the various
uses of the "REQUEST" method. If the "UID" property value in the
"REQUEST" is not found on the recipient's calendar, then the "REQUEST"
is for a new "VEVENT" calendar component. If the "UID" property value is
found on the recipient's calendar, then the
   "REQUEST"' "REQUEST" is for either a
rescheduling, an update, or a reconfirm of the "VEVENT" calendar
component.

   If the "Organizer" of the "REQUEST" method is not authorized to make
   an event request on the "Attendee's" calendar system, then an
   exception is returned in the "REQUEST-STATUS" property of a
   subsequent "REPLY" method, but no scheduling action is performed.

This method type is an iCalendar object that conforms to the following
property constraints:

     (DESCRIPTION "Event - Request" COMPONENT "VEVENT"

Component/Property  Presence
------------------- ----------------------------------------------
PRODID              MUST
VERSION             MUST be "2.0"
METHOD              MUST be "REQUEST"


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VEVENT              MUST COMPONENT = CALPROPS (
          MUST PROPERTY = PRODID, VERSION{"2.0"}, METHOD{"REQUEST"})
    ATTENDEE        MUST COMPONENT = VEVENT (
    DTSTAMP         MUST
    DTSTART         MUST PROPERTY = ATTENDEE{ ROLE=OWNER and
    ORGANIZER if
               different and "STATUS parameter absent or
               STATUS=NEEDS-ACTION on Attendees}, DESCRIPTION{MAYBE
               NULL}, DTSTAMP,DTSTART,SEQUENCE{IF NE 0}, UID
          MAY PROPERTY = ATTACH, CATEGORIES, CLASS, COMMENT, CREATED,
               DTEND, EXDATE, EXRULE, GEO, LAST-MODIFIED, LOCATION,
               PRIORITY, RDATE, RECURRENCE-ID, RELATED-TO, RESOURCES,
               RRULE, SEQUENCE{IF EQ 0}, STATUS{TENTATIVE/CONFIRMED
               /CANCELLED}, SUMMARY {MAYBE NULL}, TRANSP, URL
          NOT PROPERTY = REQUEST-STATUS)
     MAY COMPONENT = VTIMEZONE (       MUST PROPERTY = DTSTART, TZOFFSET
          MAY PROPERTY = COMMENT, DAYLIGHT, (RDATE / RRULE), TZNAME
    RECURRENCE-ID   MUST only if referring to an instance of a
                        recurring calendar component.  Otherwise it
                        must NOT PROPERTY = CREATED)
     MAY COMPONENT = VALARM ( be present.
    SEQUENCE        MUST PROPERTY = CATEGORIES, DSTART, DURATION, REPEAT
          MAY PROPERTY = ATTACH, DESCRIPTION, be present if non-zero, may be present if zero
    SUMMARY
          NOT PROPERTY = COMMENT, CREATED, LAST-MODIFIED, RELATED-TO,
               URL)         MUST be present, may be NULL
    UID             MUST

    ATTACH          MAY COMPONENT = X-TOKENS (ANY)
    CATEGORIES      MAY
    CLASS           MAY
    COMMENT         MAY
    CONTACT         MAY
    CREATED         MAY
    DESCRIPTION     MAY be present and may be NULL
    DTEND           MAY
    EXDATE          MAY
    EXRULE          MAY
    GEO             MAY
    LAST-MODIFIED   MAY
    LOCATION        MAY
    PRIORITY        MAY
    RDATE           MAY
    RELATED-TO      MAY
    RESOURCES       MAY
    RRULE           MAY
    STATUS          MAY be one of TENTATIVE/CONFIRMED
    TRANSP          MAY
    URL             MAY

    DURATION        NOT
    REQUEST-STATUS  NOT COMPONENT =

VTODO               NOT COMPONENT =
VJOURNAL            NOT COMPONENT =
VTIMEZONE           MUST be present if any date/time refers to a
                        timezone
VALARM              MAY
VFREEBUSY
     )




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3.1.2.1   REQUEST for


3.2.2.1   Rescheduling an Event

The "REQUEST" method MAY may be used to reschedule an event. A rescheduled
event involves a change to the existing event in terms of it's its time or
recurrence intervals and possibly the location or description. If the
recipient "CUA" CUA of a "REQUEST" method finds that the "UID" property value
already exists on the calendar, but that the "SEQUENCE" (or "DTSTAMP")
property value in the "REQUEST" method is greater than the value for the


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existing event, then the "REQUEST" method describes a rescheduling of
the event.

3.1.2.2   REQUEST for Update


3.2.2.2   Updating or Reconfirmation of an Event

The "REQUEST" method MAY may be used to update or reconfirm an event. An
update to an existing event does not involve changes to the time or
recurrence intervals, and might not involve a change to the location or
description for the event. If the recipient "CUA" CUA of a "REQUEST" method
finds that the "UID" property value already exists on the calendar and
that the "SEQUENCE" property value in the "REQUEST" is the same as the
value for the existing event, then the "REQUEST" method describes an
update of the event details, but no rescheduling of the event.

The update "REQUEST" method is the appropriate response to a "REFRESH"
method sent from an "Attendee" to the "Organizer" of an event.

   Unsolicited "REQUEST" methods MAY also be sent by the

The "Organizer" of an event. event may also send unsolicited "REQUEST" methods.
The unsolicited "REQUEST" methods MAY may be used to either update the details of
the event, event without rescheduling it, to update the "STATUS" property "attstat" parameter of
"Attendees", or to reconfirm the event.

3.1.2.3   REQUEST for


3.2.2.3   Delegating an Event from an "Attendee" to another CU


   The "REQUEST" method MAY be used

Some calendar and scheduling systems allow "Attendees" to delegate their
presence at an event to another
   "Calendar User". The method is used to delegate calendar user. ITIP supports this
concept using the "Attendee's" role
   (i.e., "Organizer" or "Attendee") for an event. following workflow. Any "Attendee" may delegate their
right to participate in a calendar VEVENT to another CU. The "REQUEST" method
   for delegation implication
is sent by one of that the "Attendees" delegate participates in lieu of an existing event
   request to some other "Calendar User". In order to avoid scheduling
   loops, the method MUST original "Attendee";
NOT be sent from an "Attendee" back in addition to the "Attendee". The delegator MUST notify the
"Organizer" of this action using the event. An "Attendee" MAY NOT delegate to the
   "Organizer" of the event. steps outlined below.
Implementations may support or restrict delegation as they see fit. For the purposes of this description, the "Attendee"
instance, some implementations may restrict a delegate from delegating the
   event is referred to as the "delegator". The "Attendee" receiving the
   delegation request is referred a
"REQUEST" to as the "delegatee".



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The "delegator" "Delegator" of an event MUST forward forwards the existing "REQUEST"
   method for an event to the "delegatee". The event description MUST
   include the "delegator's" up-to-date event definition.
"Delegate". The "REQUEST" method MUST also include an "ATTENDEE" property
with the calendar address of the "delegatee". "Delegate". The "delegator" "Delegator" MUST also
send a "REPLY" method back to the "Organizer" with the "delegator's" "Attendee" "Delegator's"
"ATTENDEE" property "STATUS" "attstat" parameter value set to DELEGATED. "delegated". In
addition, the
   "DELEGATED-TO" "delegated-to" parameter SHOULD MUST be included with the
calendar address of the "delegatee". A "Delegate".

In response to the delegation "REQUEST" is sent
   from request, the "delegatee" "Delegate" MUST send a "REPLY" method to
the "Organizer" and optionally, to the
   "delegator". "Delegator". The "REPLY" method from the "delegatee" "
SHOULD include
   their the "ATTENDEE" property with the "DELEGATED-FROM" "delegated-from"
parameter value of the "delegator's"calendar "Delegator's" calendar address.







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3.2.2.4   Changing the Organizer

The delegation "REQUEST" method MUST assign situation may arise where the values "Organizer" of the "RSVP"
   and "EXPECT" property parameters associated with the "delegator's"
   "ATTENDEE" property a VEVENT is no longer
able to that of the "delegatee's" "ATTENDEE" property.
   For example if the "delegator's" "ATTENDEE" property specifies
   "RSVP=TRUE;EXPECT=REQUEST", then perform the "delegatee's" "ATTENDEE"
   property MUST specify "RSVP=TRUE;EXPECT=REQUEST".

3.1.2.4   REQUEST for Delegating "Organizer" role of and abdicates without passing on
the "Organizer" role to another CU


   If someone else. When this occurs the "Owner" "Attendees"
of an existing "VEVENT" calendar component wishes to
   delegate the role of "Organizer" VEVENT may use out-of-band mechanisms to another CU, they MAY issue
   another "REQUEST" method that notifies all "Attendees" and communicate the
situation and agree upon a new "Organizer".  The new "Organizer" should
then send out a new "REQUEST" with a modified version of this change. The "Owner MUST modify several property
   parameters the VEVENT in
which the "SEQUENCE" number has been incremented and value of the "ATTENDEE"
"ORGANIZER" property including has been changed to the "ROLE", where calendar address of the
   role new
"Organizer".


3.2.2.5   Sending on Behalf of "Owner" and "Organizer" MUST be specified. Additionally, the
   "DELEGATED-TO" and "DELEGATED-FROM" parameters MUST specify Organizer

There are a number of scenarios that support the
   "Organizer" and "Owner" need for a calendar addresses. The "Owner" MAY request
   reconfirmation by incrementing the "SEQUENCE" property and setting
   the "RSVP" property parameter
user to TRUE. act on behalf of the "Organizer" without explicit role changing.
This will cause a
   reconfirmation to might be sent to the new organizer.

3.1.2.5   REQUEST for Changing case if the CU designated as "Organizer" from was sick or
unable to perform duties associated with that function. In these cases
iTIP supports the notion of one CU to another


   An "Owner" acting on behalf of another. Using
the "sent-by" parameter, a calendar user could send an existing updated "VEVENT" calendar component MAY change
REQUEST. In the
   "Organizer" from case where one "CU" to another by sending a "REQUEST" method.
   The "ROLE" property parameter value CU sends on behalf of ORGANIZER MUST be assigned to
   the new "Organizer". If another CU, the old "Organizer" is still an
"Attendee"
   then "ROLE" property parameter for that "CU" MUST be set to ATTENDEE.

3.1.2.6   REQUEST for Changing the "Owner"


   This memo does not support responses are still directed back towards the notion of changing ownership of a
   "VEVENT" calendar component.






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3.1.2.7   REQUEST Forwarded To CU designated
as "Organizer".


3.2.2.6   Forwarding to An Uninvited Calendar User CU

An "Attendee" invited to an event MAY may invite another uninvited
   "Calendar User" CU to the
event. The invited "Attendee" accomplishes this scheduling action by forwarding the
original "REQUEST" method to the uninvited "Calendar User". The forwarded "REQUEST" method need
   not include a new "ATTENDEE" property for the uninvited "Attendee". CU. Whether the uninvited "Calendar User" CU
is added to the attendee list, and thus informed of changes to the
"VEVENT" calendar component component, is an
   implementation issue.

3.1.2.8   REQUEST Updated issue left to individual
implementations. It is not required. It is important to note that when
forwarding a "REQUEST" to another CU, the forwarding "Attendee" MUST NOT
make changes to the VEVENT property set.


3.2.2.7   Updating Attendee Status


   An

The "Organizer" of an event MAY may also request an updated status from one of the "Attendees". This is achieved by the or
more "Attendees. The "Organizer" sending sends a "REQUEST" method to the
"Attendee" with and sets the "ATTENDEE;RSVP=TRUE" property sequence. parameter. The
"SEQUENCE" property for the event is not changed from its previous
value. A recipient will determine that the only change in the "REQUEST"
is that their "RSVP" property parameter indicates a request for an updated
status. The recipient SHOULD respond with a "REPLY" method indicating
their current status with respect to the "REQUEST".

   This capability MAY also be achieved by the "Organizer" sending the
   "REFRESH" method to the "Attendees".

3.1.3


3.2.3     REPLY

The "REPLY" method in a "VEVENT" calendar component is used to respond
(e.g., accept or decline) to a request "REQUEST" or to reply to a delegation request.


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"REQUEST". When used in to provide a delegation response, the "delegator" "Delegator"
SHOULD include the calendar address of the
   "delegatee" "Delegate" on the "DELEGATED-TO" "delegated-
to" property parameter  of the
   "delegator's" "Delegator's" "ATTENDEE" property. The "delegatee"
"Delegate" SHOULD include the calendar address of the "delegator" "Delegator" on the "DELEGATED-FROM"
"delegated-from" property parameter of the "delegatee's" "Delegate's" "ATTENDEE"
property.

The "REPLY" method MAY may also be used to respond to an unsuccessful
"REQUEST" method. Depending on the value of the "REQUEST-STATUS"
property no scheduling action MAY may have been performed.

The "Organizer" of an event MAY may receive the "REPLY" method from a
   "Calendar User" CU not
in the original "REQUEST". For example, a "REPLY"
   method MAY may be received from a "delegatee"
"Delegate" to an event. In addition, the "REPLY" method MAY may be received
from an unknown "Calendar User",
   forwarded the "REQUEST" from an invited "Attendee". CU (a "Party Crasher"). This uninvited "Attendee" MAY may be
accepted, or the "Organizer" MAY may cancel the event for the uninvited
"Attendee" by sending them a "CANCEL" method to the
   univited uninvited "Attendee".




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The "Organizer" may also receive a "REPLY" from one CU on behalf of
another. Like the scenario enumerated above for the "Organizer",
"Attendees" may have another CU respond on their behalf. This is done
using the "sent-by" parameter.

The optional properties listed in the table below (those listed as
"MAY") MUST NOT be changed from those of the original request.  If
property changes are desired the COUNTER message must be used.

This method type is an iCalendar object that conforms to the following
property constraints:

     (DESCRIPTION "Event - Reply" COMPONENT "VEVENT" METHOD "REPLY"

Component/Property  Presence
------------------- ----------------------------------------------
PRODID              MUST COMPONENT = CALPROPS (
          MUST PROPERTY = PRODID, VERSION{"2.0"}, METHOD{"REPLY"})
VERSION             MUST COMPONENT = be "2.0"
METHOD              MUST be "REPLY"

VEVENT (              MUST PROPERTY = ATTENDEE{MUST
    ATTENDEE        MUST be the address of ATTENDEE
               replying}, DTSTAMP, SEQUENCE{IF NE 0}, UID{UID
               associated with the Attendee replying.
    DTSTAMP         MUST
    ORGANIZER       MUST
    RECURRENCE-ID   MUST only if referring to an instance of a
                        recurring calendar component.  Otherwise it
                        must NOT be present.
    SEQUENCE        MUST if non-zero
    UID             MUST be the UID of the original REQUEST} REQUEST

    ATTACH          MAY
    COMMENT         MAY
    CONTACT         MAY
    EXDATE          MAY
    EXRULE          MAY
    REQUEST-STATUS  MAY

    CATEGORIES      MAY


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    CLASS           MAY
    CREATED         MAY
    DESCRIPTION     MAY
    DTSTART         MAY
    DTEND           MAY
    DURATION        MAY
    GEO             MAY
    LAST-MODIFIED   MAY
    PRIORITY        MAY
    RELATED-TO      MAY
    RESOURCES       MAY
    RDATE           MAY
    RRULE           MAY
    STATUS          MAY PROPERTY = COMMENT{provides comment from ATTENDEE to
               "Organizer"}, EXDATE, EXRULE, RECURRENCE-ID, REQUEST-
               STATUS, SEQUENCE{IF EQ 0},
    SUMMARY {MAYBE NULL},         MAY
    TRANSP          MAY
    URL
          NOT PROPERTY = ATTACH, CATEGORIES, CLASS, CREATED,
               DESCRIPTION, DTSTART, DTEND, GEO, LAST-MODIFIED,
               PRIORITY, RELATED-TO, RESOURCES, RDATE, RRULE, STATUS,
               SUMMARY, TRANSP, URL)             MAY COMPONENT =

VTIMEZONE           MUST be present if any date/time refers to a
                        timezone
X-TOKENS (ANY)            NOT COMPONENT =
VTODO               NOT COMPONENT =
VJOURNAL            NOT COMPONENT =
VFREEBUSY           NOT COMPONENT = VTIMEZONE
     NOT COMPONENT =
VALARM
     )

3.1.4     CANCEL              NOT


3.2.4     ADD

The "CANCEL" "ADD" method in a "VEVENT" calendar component is used to send
   a cancellation notice of add one or
more instances to an existing event request to "VEVENT". Unlike the
   "Attendees". The message is sent by "REQUEST" method,
when using issuing an "ADD" method, the "Organizer" of an event to does not send the "Attendees" of
full "VEVENT" description; only the event. For new instance(s). The "ADD" method is
especially useful if there are instance-specific properties to be
preserved in a recurring event, either the whole
   event "VEVENT". For instance, an "Organizer" may have
originally scheduled a weekly Thursday meeting. At some point, several
instances changed. Location or start time may have changed, or some
instances of may have unique "DESCRIPTION" properties. The "ADD" method
allows the "Organizer" to add new instances to an existing event MAY be cancelled. To cancel using a
single ITIP message without redefining the
   complete range of entire recurring event, pattern.

The "UID" must be that of the existing event. If the "UID" property
value for the
   event MUST be specified in the "CANCEL" method. In order to cancel an
   individual instance of "ADD" is not found on the event, recipient's calendar, then the "RECURRENCE-ID" property value
   for
recipient SHOULD send a "REFRESH" to the event MUST be specified "Organizer" in the "CANCEL" method. In order to
   cancel a sequence be
updated with the latest version of recurring events, either the"RECURRENCE-ID"
   property for the first event instance in "VEVENT".  If an "Attendee"
implementation does not support the sequence MUST be
   specified "ADD" method it should respond with the "RANGE" property parameter
a "REQUEST-STATUS" value of THISANDPRIOR
   or THISANDFUTURE to indicate cancellation of the event instances
   before 5.3 and after the first event instance, respectively. Lastly,
   individual recurrence instances MAY be cancelled by specifying
   multiple"RECURRENCE-ID" properties corresponding to the instances to
   be cancelled. ask for a "REFRESH".

This method type is an iCalendar object that conforms to the following
property constraints:

     (DESCRIPTION "Event - Cancel" COMPONENT "VEVENT" METHOD "CANCEL"

Component/Property  Presence
------------------- ----------------------------------------------
PRODID              MUST COMPONENT = CALPROPS (
          MUST PROPERTY = PRODID, VERSION{"2.0"}, METHOD{"CANCEL"})


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     MUST COMPONENT = VEVENT (                       March 13, 1998


VERSION             MUST PROPERTY = DTSTAMP, SEQUENCE{IF NE 0}, UID{UID
               associated with be "2.0"
METHOD              MUST be "ADD"
VEVENT              MUST
DTSTAMP         MUST
    DTSTART         MUST
    ORGANIZER       MUST
    SEQUENCE        MUST be greater than 0
    SUMMARY         MUST be present, may be NULL
    UID             MUST match that of the original REQUEST} event

    ATTACH          MAY PROPERTY = COMMENT{provides comment from "Organizer" to
               ATTENDEE}, EXDATE, EXRULE, RECURRENCE-ID, SEQUENCE{IF EQ
               0}, STATUS{CANCELLED}
          NOT PROPERTY = ATTACH, ATTENDEE, CATEGORIES, CLASS, CREATED,
               DESCRIPTION, DTSTART, DTEND, GEO, LAST-MODIFIED,
               PRIORITY, RDATE, RELATED-TO, RESOURCES, REQUEST-STATUS,
               RRULE, SUMMARY, TRANSP, URL)
    ATTENDEE        MAY COMPONENT = X-TOKENS (ANY)
    CATEGORIES      MAY
    CLASS           MAY
    COMMENT         MAY
    CONTACT         MAY
    CREATED         MAY
    DESCRIPTION     MAY be present and may be NULL
    DTEND           MAY
    EXDATE          MAY
    EXRULE          MAY
    GEO             MAY
    LAST-MODIFIED   MAY
    LOCATION        MAY
    PRIORITY        MAY
    RDATE           MAY
    RELATED-TO      MAY
    RESOURCES       MAY
    RRULE           MAY
    STATUS          MAY be one of TENTATIVE/CONFIRMED
    TRANSP          MAY
    URL             MAY

    DURATION        NOT
    RECURRENCE-ID   NOT
    REQUEST-STATUS  NOT COMPONENT =

VTODO               NOT COMPONENT =
VJOURNAL            NOT COMPONENT = VFREEBUSY
     NOT COMPONENT =
VTIMEZONE
     NOT COMPONENT =           MUST be present if any date/time refers to a
                        timezone
VALARM
     )

3.1.5     REFRESH              MAY
VFREEBUSY           NOT
X-TOKENS            MAY


3.2.5     CANCEL

The "REFRESH" "CANCEL" method in a "VEVENT" calendar component is used by
   "Attendees" to send a
cancellation notice of an existing event to request an updated description
   from to the event "Organizer". "Attendees". The "REFRESH" method MUST specify
message is sent by the
   "UID" property corresponding to "Organizer" of the event. For a recurring event,
either the whole event needing update. A
   recurrence instance or instances of an event MAY may be requested by specifying cancelled. To
cancel the
   "RECURRENCE-ID" complete range of recurring event, the "UID" property corresponding to value
for the associated event. The
   "Organizer" event MUST respond with the latest description be specified and version of a "RECURRENCE-ID" MUST NOT be


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specified in the event. This method is intended "CANCEL" method. In order to facilitate machine processing
   of event update requests by an "Attendee".

   This method type is cancel an iCalendar object that conforms to individual
instance of the
   following event, the "RECURRENCE-ID" property constraints:

     (DESCRIPTION "Event - Refresh" COMPONENT "VEVENT" METHOD "REFRESH"

     MUST COMPONENT = CALPROPS (
          MUST PROPERTY = PRODID, VERSION{"2.0"}, METHOD{"REFRESH"})
     MUST COMPONENT = VEVENT ( value for the event
MUST PROPERTY = ATTENDEE{address of requestor}, DTSTAMP,
               SEQUENCE{IF NE 0}, UID{UID associated with original
               REQUEST}
          MAY PROPERTY = COMMENT{provides comment from ATTENDEE to
               "Organizer"}, RECURRENCE-ID, SEQUENCE{IF EQ 0}
          NOT PROPERTY = ATTACH, CATEGORIES, CLASS, CREATED,
               DESCRIPTION, DTSTART, DTEND, EXDATE, EXRULE, GEO,
               LAST-MODIFIED, PRIORITY, RDATE,RELATED-TO, RESOURCES,
               REQUEST-STATUS, RRULE,SUMMARY, STATUS, TRANSP, URL)
     MAY COMPONENT = X-TOKENS (ANY)
     NOT COMPONENT = VTODO
     NOT COMPONENT = VJOURNAL
     NOT COMPONENT = VFREEBUSY
     NOT COMPONENT = VTIMEZONE
     NOT COMPONENT = VALARM


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     )

3.1.6     COUNTER


   The "COUNTER" method be specified in the "CANCEL" method.

There are two options for canceling a sequence of instances of a
recurring "VEVENT" calendar component is used by an
   "Attendee" of an existing event to submit to component:

(a)    the "Organizer" a
   counter proposal to "RECURRENCE-ID" property for an instance in the event description. The "Attendee" sequence MUST send be
  specified with the message "RANGE" property parameter value of THISANDPRIOR
  (or THISANDFUTURE)  to the "Organizer" indicate cancellation of the event.

   The counter proposal is an iCalendar object consisting of a VEVENT specified
  "VEVENT" calendar component describing the complete description of the
   alternate event.

   The "Organizer" rejects the counter proposal by sending the
   "Attendee" a VEVENT "DECLINE-COUNTER" method. The "Organizer" accepts
   the counter proposal by sending and all of the "Attendees" to the event a
   VEVENT "REQUEST" method rescheduling the event. In the later case,
   the "Organizer" SHOULD reset the instances before (or after); or

(b)    individual "RSVP" property parameter
   values to TRUE on each "ATTENDEE" property in order to force a
   response recurrence instances may be cancelled by specifying
  multiple "RECURRENCE-ID" properties corresponding to the "Attendees". instances to
  be cancelled.

This method type is an iCalendar object that conforms to the following
property constraints:

     (DESCRIPTION "Event - Counter Proposal" COMPONENT "EVENT"
     METHOD "COUNTER"

Component/Property  Presence
------------------- ----------------------------------------------
PRODID              MUST COMPONENT = CALPROPS (
          MUST PROPERTY = PRODID, VERSION{"2.0"}, METHOD{"COUNTER"})
VERSION             MUST COMPONENT = be "2.0"
METHOD              MUST be "CANCEL"

VEVENT (              MUST PROPERTY = ATTENDEE{STATUS parameter absent or
               STATUS=NEEDS ACTION, Owner and Organizer
    DTSTAMP         MUST
    ORGANIZER       MUST
    RECURRENCE-ID   MUST only if different,
               MAY also be used referring to propose other  "Attendees"},
               DESCRIPTION{MAYBE NULL}, DTSTAMP, DTSTART,
               SEQUENCE{IF NE 0}, UID{MUST one or more instances of
                        a recurring calendar component.  Otherwise it
                        MUST NOT be present.
    SEQUENCE        MUST
    UID             MUST be the UID associated with of the original REQUEST being countered}

    COMMENT         MAY PROPERTY = ATTACH, CATEGORIES, CLASS, COMMENT{provides a
               comment from the ATTENDEE
    STATUS          Must be set to the "Organizer"}, CREATED,
               DTEND, EXDATE, EXRULE, GEO, LAST-MODIFIED, LOCATION,
               PRIORITY, RDATE, RECURRENCE-ID, RELATED-TO, RESOURCES,
               RRULE, SEQUENCE{IF EQ 0}, STATUS{TENTATIVE/CONFIRMED/
               CANCELLED} , SUMMARY {MAYBE NULL}, TRANSP, URL "Cancelled". If uninviting specific
                        "Attendees" then MUST NOT PROPERTY = COMPLETED, DUE, DURATION, REQUEST-STATUS) be included.

    ATTACH          MAY COMPONENT = VTIMEZONE (
          MUST PROPERTY = DTSTART, TZOFFSET
    ATTENDEE        MAY PROPERTY = COMMENT, DAYLIGHT, (RDATE / RRULE), TZNAME
          NOT PROPERTY = CREATED)
    CATEGORIES      MAY COMPONENT = VALARM (IF COMPONENT EXISTS
          MUST PROPERTY = CATEGORIES, DSTART, DURATION, REPEAT
    CLASS           MAY PROPERTY = ATTACH, DESCRIPTION, SUMMARY
     NOT PROPERTY = COMMENT, CREATED, LAST-MODIFIED, RELATED-TO, URL)
    CONTACT         MAY
    CREATED         MAY
    DESCRIPTION     MAY
    DTSTART         MAY
    DURATION        MAY
    DTEND           MAY
    EXDATE          MAY
    EXRULE          MAY
    GEO             MAY
    LAST-MODIFIED   MAY
    PRIORITY        MAY
    RELATED-TO      MAY COMPONENT = X-TOKENS (ANY)
     NOT COMPONENT = VTODO


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    REQUEST-STATUS  MAY
    RESOURCES       MAY
    RDATE           MAY
    RRULE           MAY
    STATUS          MAY
    SUMMARY         MAY
    TRANSP          MAY
    URL             MAY

VTIMEZONE           MUST be present if any date/time refers to a
                        timezone

X-TOKENS            MAY
VTODO               NOT COMPONENT =
VJOURNAL            NOT COMPONENT =
VFREEBUSY
     )

3.1.7     DECLINECOUNTER           NOT
VALARM              NOT


3.2.6     REFRESH

The "DECLINE-COUNTER" "REFRESH" method in a "VEVENT" calendar component is used by the "Organizer"
"Attendees" of an existing event to reject a counter proposal submitted
   by request an "Attendee". The "Organizer" MUST send the "DECLINE-COUNTER"
   message to the "Attendee" that sent the "COUNTER" method to updated description from
the event "Organizer". The counter proposal is an iCalendar object consisting of a VEVENT
   calendar component describing "REFRESH" method must specify the complete description "UID"
property of the
   alternate event.

   The "Organizer" rejects the counter proposal event to update. A recurrence instance of an event may
be requested by sending specifying the
   "Attendee" a "DECLINE-COUNTER" method. "RECURRENCE-ID" property corresponding to
the associated event. The "Organizer" accepts responds with the
   counter proposal by sending all latest
description and version of the "Attendees" to the event a
   "REQUEST" method; rescheduling the event. Since this

This method type is a rescheduled
   event, an iCalendar object that conforms to the "SEQUENCE" following
property value will constraints:

Component/Property  Presence
------------------- ----------------------------------------------
PRODID              MUST
VERSION             MUST be "2.0"
METHOD              MUST be "REFRESH"

VEVENT              MUST
    ATTENDEE        MUST be incremented. In the
   later case, the "Organizer" address of requestor
    DTSTAMP         MUST
    RECURRENCE-ID   MUST only if referring to an instance of a
                        recurring calendar component.  Otherwise it
                        must NOT be present.
    UID             MUST be the UID associated with original
                        REQUEST

    COMMENT         MAY

    ATTACH          NOT
    ATEGORIES       NOT
    CLASS           NOT
    CONTACT         MAY
    CREATED         NOT


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    DESCRIPTION     NOT
    DTSTART         NOT
    DTEND           NOT
    DURATION        NOT
    EXDATE          NOT
    EXRULE          NOT
    GEO             NOT
    LAST-MODIFIED   NOT
    ORGANIZER       NOT
    PRIORITY        NOT
    RDATE           NOT
    RELATED-TO      NOT
    RESOURCES       NOT
    REQUEST-STATUS  NOT
    RRULE           NOT
    SEQUENCE        NOT
    SUMMARY         NOT
    STATUS          NOT
    TRANSP          NOT
    URL             NOT

VTIMEZONE           MUST be present if any date/time refers to a
                        timezone

X-TOKENS            MAY
VTODO               NOT
VJOURNAL            NOT
VFREEBUSY           NOT
VALARM              NOT


3.2.7     COUNTER

The "COUNTER" method for a "VEVENT" calendar component is used by an
"Attendee" of an existing event to submit to the "Organizer" a counter
proposal to the event description. The "Attendee" sends this message to
the "Organizer" of the event.

The counter proposal is an iCalendar object consisting of a VEVENT
calendar component describing the complete description of the alternate
event.

The "Organizer" rejects the counter proposal by sending the "Attendee" a
VEVENT "DECLINE-COUNTER" method. The "Organizer" accepts the counter
proposal by sending all of the "Attendees" to the event a VEVENT
"REQUEST" method rescheduling the event. In the latter case, the
"Organizer" SHOULD reset the individual "RSVP" property parameter values
to TRUE on all of the each "ATTENDEE" properties; property in order to force a response by the
"Attendees".

This method type is an iCalendar object that conforms to the following
property constraints:

     (DESCRIPTION "Event - Cancel" COMPONENT "VEVENT" METHOD
          "DECLINECOUNTER"

Component/Property  Presence


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------------------- ----------------------------------------------
PRODID              MUST COMPONENT = CALPROPS (
          MUST PROPERTY = PRODID, VERSION{"2.0"},METHOD{
          "DECLINECOUNTER"})
VERSION             MUST COMPONENT = be "2.0"
METHOD              MUST be "COUNTER"

VEVENT (              MUST PROPERTY = DTSTAMP, SEQUENCE{IF NE 0}, UID{same UID
               specified In Original REQUEST and subsequent COUNTER}
          MAY PROPERTY = COMMENT{provides comment from "Organizer" to
               ATTENDEE}, RECURRENCE-ID, REQUEST-STATUS, SEQUENCE{IF EQ
               0}
          NOT PROPERTY = ATTACH, ATTENDEE, CATEGORIES, CLASS, CREATED,
               DESCRIPTION, DTSTART, DTEND, EXDATE, EXRULE, GEO,
               LAST-MODIFIED, PRIORITY, RDATE, RELATED-TO, RESOURCES,
               RRULE,STATUS, SUMMARY, TRANSP, URL)
     MAY COMPONENT = X-TOKENS (ANY)
    DTSTAMP         MUST
    RECURRENCE-ID   MUST only if referring to an instance of a
                        recurring calendar component.  Otherwise it
                        must NOT COMPONENT = be present.
    SEQUENCE        MUST be present if non-zero, MAY be present if zero
    SUMMARY         MUST be present may be NULL
    UID             MUST be the UID associated with the REQUEST
                        being countered

    ATTACH          MAY
    ATTENDEE        MAY be used to propose other "Attendees"
    CATEGORIES      MAY
    CLASS           MAY
    COMMENT         MAY
    CONTACT         MAY
    CREATED         MAY
    DESCRIPTION     MAY be present, may be NULL
    DTSTART         MAY
    DTEND           MAY
    EXDATE          MAY
    EXRULE          MAY
    GEO             MAY
    LAST-MODIFIED   MAY
    LOCATION        MAY
    PRIORITY        MAY
    RDATE           MAY
    RELATED-TO      MAY
    RESOURCES       MAY
    RRULE           MAY
    STATUS          MAY
    TRANSP          MAY
    URL             MAY

    COMPLETED       NOT
    DUE             NOT
    DURATION        NOT
    ORGANIZER       NOT
    REQUEST-STATUS  NOT

VTIMEZONE           MUST be present if any date/time refers to a
                        timezone
VALARM              MAY

X-TOKENS            MAY
VTODO               NOT COMPONENT =
VJOURNAL            NOT COMPONENT =
VFREEBUSY           NOT COMPONENT = VTIMEZONE
     NOT COMPONENT = VALARM
     )



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3.2 Methods For VFREEBUSY Component


   This section defines the property set for                       March 13, 1998


3.2.8     DECLINECOUNTER

The "DECLINE-COUNTER" method in a "VEVENT" calendar component is used by
the methods that are
   applicable "Organizer" of an event to reject a counter proposal submitted by an
"Attendee". The "Organizer" must send the "VFREEBUSY" calendar component. Each of "DECLINE-COUNTER" message to
the methods
   is defined using a grammar "Attendee" that specifies sent the property constraints
   that define "COUNTER" method to the particular method. "Organizer".

This memo only addresses the transfer of busy time information.
   Applications desiring free time information MUST infer this from
   available busy time information.

   The busy time information within the method type is an iCalendar object MAY that conforms to the following
property constraints:

Component/Property  Presence
------------------- ----------------------------------------------
PRODID              MUST
VERSION             MUST be grouped
   into more than one "VFREEBUSY" calendar component. This capability
   allows busy time periods to "2.0"
METHOD              MUST be grouped according "DECLINECOUNTER"

VEVENT              MUST
    DTSTAMP         MUST
    ORGANIZER       MUST
    RECURRENCE-ID   MUST only if referring to some common
   periodicity, such as an instance of a
                        recurring calendar week, month, or year. In this case,
   each "VFREEBUSY" calendar component component.  Otherwise it
                        must NOT be present.
    SEQUENCE        MUST include the "ATTENDEE",
   "DTSTART" and "DTEND" properties if non-zero, MAY be present if zero
    UID             MUST, same UID specified in order to specify the source of
   the busy time information and the date original
                        REQUEST and time interval over which
   the busy time information covers.

   The "FREEBUSY" property value subsequent COUNTER

    COMMENT         MAY include a list of values, separated
   by the COMMA character (ASCII decimal 44). Alternately, multiple busy
   time periods
    REQUEST-STATUS  MAY be specified with multiple instances of the
   "FREEBUSY" property. Both forms

    ATTACH          NOT
    ATTENDEE        NOT
    CATEGORIES      NOT
    CLASS           NOT
    CONTACT         NOT
    CREATED         NOT
    DESCRIPTION     NOT
    DTSTART         NOT
    DTEND           NOT
    DURATION        NOT
    EXDATE          NOT
    EXRULE          NOT
    GEO             NOT
    LAST-MODIFIED   NOT
    PRIORITY        NOT
    RDATE           NOT
    RELATED-TO      NOT
    RESOURCES       NOT
    RRULE           NOT
    STATUS          NOT
    SUMMARY         NOT
    TRANSP          NOT
    URL             NOT

VTIMEZONE           MUST be supported by implementations
   conforming present if any date/time refers to this document. Duplicate busy time periods SHOULD NOT
   be specified in an iCalendar object. However, two different busy time
   periods a


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                        timezone
X-TOKENS            MAY overlap.

   "FREEBUSY" properties SHOULD be sorted such that their values are in
   ascending order, based on the start time, and then the end time, with
   the earliest periods first. For example, today's busy time
   information SHOULD appear after yesterday's busy time information.
   And
VTODO               NOT
VJOURNAL            NOT
VFREEBUSY           NOT
VALARM              NOT



3.3 Methods For VFREEBUSY Components

This section defines the busy time property set for this half hour SHOULD appear after the busy
   time for earlier today.

   Since events MAY span methods that are
applicable to the "VFREEBUSY" calendar component. Each of the methods is
defined using a day boundary, free restriction table.

This document only addresses the transfer of busy time period MAY also
   span a day boundary. Individual "A" requests busy information.
Applications desiring free time information MUST infer this from
   individuals "B", "C" and "D". Individual "B" and "C" replies with
available busy time data to individual "A". Individual "D" does not support information.

The busy time requests and does not reply with any data. If the transport
   binding supports exception messages, then a "unsupported capability"
   message is returned by individual "D" to individual "A".

   The following summarizes the methods that are defined for information within the iCalendar object MAY be grouped
into more than one "VFREEBUSY" calendar component.

 |================|==================================================|
 | Method         |  Description                                     |
 |================|==================================================|
 | PUBLISH        | Publish unsolicited busy time data.              |
 | REQUEST        | Request This capability
allows busy time data.                          |
 | REPLY          | Reply periods to be grouped according to some common
periodicity, such as a busy time request.                    |
 |================|==================================================|


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3.2.1     PUBLISH


   The "PUBLISH" method in a calendar week, month, or year. In this case, each
"VFREEBUSY" calendar component is used to
   publish busy time data. The method MAY be sent from one "Calendar
   User" MUST include the "ATTENDEE", "DTSTART"
and "DTEND" properties in order to any other. The purpose specify the source of the method is to provide a message
   for sending unsolicited busy time data. That is,
information and the date and time interval over which the busy time data
   is not being sent as
information covers.

The "FREEBUSY" property value MAY include a "REPLY" to the receipt list of a "REQUEST" method.

   Busy time intervals are represented values, separated by individual
the COMMA character (ASCII decimal 44). Alternately, multiple busy time
periods MAY be specified with multiple instances of the "FREEBUSY"
property. There is one occurrence of the property for each
   busy time interval. Both forms MUST be supported by implementations conforming to
this document. Duplicate busy time periods SHOULD NOT be
   returned. specified in an
iCalendar object. However, two different busy time periods MAY overlap.

   The "FREEBUSY" property value MAY include a list of values, separated
   by the COMA character (ASCII decimal 44).

"FREEBUSY" properties SHOULD should be sorted such that their values are in
ascending order, from based on the most recent to past. start time, and then the end time, with
the earliest periods first. For example, today's busy time information SHOULD
should appear after yesterday's busy time information. And the busy time
for this half hour SHOULD half-hour should appear after the busy time for earlier today.

Since events MAY may span a day boundary, free busy time period MAY may also
span a day boundary.

   The busy time periods MAY be grouped into more than one "VFREEBUSY"
   calendar component. This capability allows Individual "A" requests busy time periods to be
   grouped according to some common periodicity, such as a calendar
   week, month, or year. In this case, each "VFREEBUSY" calendar
   component MUST include the "ATTENDEE", "DTSTART" and "DTEND"
   properties in order to specify the originator from individuals
"B", "C" and date "D". Individual "B" and time
   interval for the "C" replies with busy time information.

   The "ATTENDEE" property MUST be specified in the data to
individual "A". Individual "D" does not support busy time
   information. The value is the "Calendar User" address of the
   originator of requests and
does not reply with any data. If the busy time information.

   This method type is transport binding supports
exception messages, then individual "D" returns an iCalendar object that conforms "unsupported
capability" message to the individual "A".

The following property constraints:

     (DESCRIPTION "Busy - Busy Time Publish" COMPONENT "VFREEBUSY"
          METHOD "PUBLISH"

     MUST COMPONENT = CALPROPS (
          MUST PROPERTY = PRODID, VERSION{"2.0"}, METHOD{"PUBLISH"})
     MUST COMPONENT = VFREEBUSY (
          MUST PROPERTY = ATTENDEE{address of originator of busy time
               data},FREEBUSY{values MUST all be of summarizes the same data type.
               Multiple instances methods that are allowed. Multiple instances MUST
               be sorted in ascending order. Values MAY NOT overlap},
               RELATED-TO{refers to another related VFREEBUSY defined for the
"VFREEBUSY" calendar component.


|================|==================================================|


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               component},
          MAY PROPERTY = COMMENT{comment from attendee to originator of
               request}, CREATED{specifies when the busy time data was
               created}, DTSTART{represents start of interval for busy
               time data}, DTEND{represents end of interval for                       March 13, 1998


| Method         |  Description                                     |
|================|==================================================|
| PUBLISH        | Publish unsolicited busy time data},LAST-MODIFIED{specifies when data.              |
| REQUEST        | Request busy time data
               was last modified}, SEQUENCE{IF EQ 0}, URL{specifies data.                          |
| REPLY          | Reply to a busy time URL}
          NOT PROPERTY = DTSTAMP, DURATION, REQUEST-STATUS, SEQUENCE,
               UID)
     MAY COMPONENT = VTIMEZONE (
          MUST PROPERTY = DTSTART, TZOFFSET
          MAY PROPERTY = COMMENT, DAYLIGHT, (RDATE / RRULE), TZNAME
          NOT PROPERTY = CREATED)
     MAY COMPONENT = X-TOKENS (ANY)
     NOT COMPONENT = VEVENT
     NOT COMPONENT = VTODO
     NOT COMPONENT = VJOURNAL
     NOT COMPONENT = VALARM
     )

3.2.2     REQUEST request.                    |
|================|==================================================|


3.3.1     PUBLISH

The "REQUEST" "PUBLISH" method in a "VFREEBUSY" calendar component is used to
   ask a "Calendar User" for their
publish busy time information. data. The request
   MAY method may be for a busy time information bounded by sent from one CU to any other.
The purpose of the method is to provide a specific date and
   time interval.

   This message only permits requests for sending
unsolicited busy time information. The
   message is sent from a "Calendar User" requesting data. That is, the busy time
   information to one or more intended recipients.

   An "ATTENDEE" property MUST be included for the originator of the
   request and each of the intended recipients that the method data is not being
sent
   to. The originator is indicated with an "ATTENDEE" property parameter
   sequence as a "REPLY" to the receipt of ";ROLE=ORGANIZER". a "REQUEST" method.

The recipients are indicated with an "ATTENDEE" property parameter sequence of ";ROLE=ATTENDEE". The
   requests MAY must be fanned out specified in separate messages to the recipients,
   with each "REQUEST" method only including the associated "ATTENDEE"
   properties for busy time information.
The value is the recipients CU address of the message.

   If the originator of the "REQUEST" method is not authorized to make a
   busy time request on the recipient's calendar system, then an
   exception message is returned in a "REPLY" method, but no busy time
   data need be returned.
information.

This method type is an iCalendar object that conforms to the following
property constraints:

     (DESCRIPTION "FREEBUSY - Request For Busy Time" COMPONENT
          "VFREEBUSY" METHOD "REQUEST"


Component/Property  Presence
------------------- ----------------------------------------------
PRODID              MUST COMPONENT = CALPROPS (


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VERSION             MUST PROPERTY = PRODID, VERSION{"2.0"}, METHOD{"REQUEST"}) be "2.0"
METHOD              MUST COMPONENT = be "PUBLISH"

VFREEBUSY (           MUST PROPERTY = ATTENDEE{Attendee
    ATTENDEE        MUST contain the address of originator of
                        busy time data
    DTSTAMP         MUST
    FREEBUSY        MUST be BUSYTIME. Multiple instances for are allowed.
                        Multiple instances must be sorted in ascending
                        order.
    ATTACH          MAY
    RELATED-TO      MAY
    COMMENT         MAY
    CONTACT         MAY
    CREATED         MAY specifies when the Owner and
               Organizer if different and busy time data was
                        Created
    DTSTART         MAY be present to represent start of the intended recipient
                        interval for busy time data
    DTEND           MAY be present to represent the end of
                        the
               request}, DTSTAMP, DTSTART, DTEND,SEQUENCE{IF NE 0}, UID interval for busy time data
    GEO             MAY PROPERTY = SEQUENCE{IF EQ 0}
          NOT PROPERTY = COMMENT, CREATED, DURATION, FREEBUSY,
               LAST-MODIFIED, RELATED-TO, URL, REQUEST-STATUS)
    ORGANIZER       MAY COMPONENT = VTIMEZONE (
          MUST PROPERTY = DTSTART, TZOFFSET
    URL             MAY PROPERTY = COMMENT, DAYLIGHT, (RDATE / RRULE), TZNAME (specifies busy time URL)

    CATEGORIES      NOT PROPERTY = CREATED)
     MAY COMPONENT
    CLASS           NOT
    DESCRIPTION     NOT


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    DURATION        NOT
    EXDATE          NOT
    EXRULE          NOT
    LAST-MODIFIED   NOT
    PRIORITY        NOT
    RDATE           NOT
    RECURRENCE-ID   NOT
    REQUEST-STATUS  NOT
    RESOURCES       NOT
    RRULE           NOT
    SEQUENCE        NOT
    STATUS          NOT
    SUMMARY         NOT
    TRANSP          NOT
    UID             NOT

VTIMEZONE           MUST be present if any date/time refers to a
                        timezone
X-TOKENS (ANY)            NOT COMPONENT =
VEVENT              NOT COMPONENT =
VTODO               NOT COMPONENT =
VJOURNAL            NOT COMPONENT =
VALARM
     )

3.2.3     REPLY              NOT


3.3.2     REQUEST

The "REPLY" "REQUEST" method in a "VFREEBUSY" calendar component is used to
   respond to an existing busy time request. The method is sent from a
   recipient of ask
a "Calendar User" for their busy time request back to the originator of the
   request. information. The originator of the request is specified by the "ATTENDEE"
   property parameter sequence of ";ROLE=ORGANIZER".

   The "REPLY" method MAY also may be used to respond to an unsuccessful
   "REQUEST" method. Depending on the "REQUEST-STATUS" value, no
for a busy time information MAY be returned.

   Busy time intervals are represented bounded by individual instances of the
   "FREEBUSY" property. There is one occurrence of the property for each
   busy a specific date and time
interval. Duplicate busy time periods SHOULD NOT be
   returned. However, two different

This message only permits requests for busy time periods MAY overlap. information. The "FREEBUSY" property value MAY include a list of values, separated
   by the COMA character (ASCII decimal 44).

   "FREEBUSY" properties SHOULD be sorted such that their values are in
   ascending order,
message is sent from a "Calendar User" requesting the most recent to past. For example, today's busy time
information SHOULD appear after yesterday's busy time
   information. And to one or more intended recipients.

If the busy time for this half hour SHOULD appear after originator of the busy time for earlier today.

   Since events MAY span "REQUEST" method is not authorized to make a day boundary, free
busy time period MAY also
   span request on the recipient's calendar system, then an exception
message SHOULD be returned in a day boundary.

   The "REPLY" method, but no busy time periods MAY data
need be grouped into more than one "VFREEBUSY"
   calendar component. returned.

This capability allows busy time periods method type is an iCalendar object that conforms to the following
property constraints:


Component/Property  Presence
------------------- ----------------------------------------------
PRODID              MUST
VERSION             MUST be
   grouped according to some common periodicity, such as a calendar
   week, month, or year. In this case, each "VFREEBUSY" calendar
   component "2.0"
METHOD              MUST include be "REQUEST"

VFREEBUSY           MUST
    ATTENDEE        MUST contain the "ATTENDEE", "DTSTART" and "DTEND" address of the calendar store
                        for which busy time is being requested.


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   properties in order to identify the source and date and time range
   for                       March 13, 1998


    DTEND           MUST
    DTSTAMP         MUST
    DTSTART         MUST
    ORGANIZER       MUST be the busy time data.

   The "ATTENDEE" property request originator's address

    ATTACH          MAY
    COMMENT         MAY
    CONTACT         MAY
    GEO             MAY
    URL             MAY

    CATEGORIES      NOT
    CLASS           NOT
    CREATED         NOT
    DESCRIPTION     NOT
    DURATION        NOT
    EXDATE          NOT
    EXRULE          NOT
    FREEBUSY        NOT
    LAST-MODIFIED   NOT
    PRIORITY        NOT
    RDATE           NOT
    RECURRENCE-ID   NOT
    RELATED-TO      NOT
    REQUEST-STATUS  NOT
    RESOURCES       NOT
    RRULE           NOT
    SEQUENCE        NOT
    STATUS          NOT
    SUMMARY         NOT
    TRANSP          NOT
    UID             NOT

VTIMEZONE           MUST be specified present if any date/time refers to a

X-TOKENS            MAY
VEVENT              NOT
VTODO               NOT
VJOURNAL            NOT
VALARM              NOT


3.3.3     REPLY

The "REPLY" method in the a "VFREEBUSY" calendar component is used to
respond to a busy time reply. request. The
   value method is sent by the fully qualified RFC 822 address recipient of a
busy time request to the originator of the recipient
   replying request.

The "REPLY" method may also be used to respond to an unsuccessful
"REQUEST" method. Depending on the "REQUEST-STATUS" value, no busy time request.
information may be returned.

This method type is an iCalendar object that conforms to the following
property constraints:

     (DESCRIPTION "FreeBusy - Busy Time Reply" COMPONENT "VFREEBUSY"
     METHOD "REPLY"


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Component/Property  Presence
------------------- ----------------------------------------------
PRODID              MUST COMPONENT = CALPROPS (
          MUST PROPERTY = PRODID, VERSION{"2.0"}, METHOD{"REPLY"})
VERSION             MUST COMPONENT = be "2.0"
METHOD              MUST be "REPLY"

VFREEBUSY (           MUST PROPERTY = ATTENDEE{address
    ATTENDEE        MUST (address of recipient replying},
               DTSTAMP, DTSTART, DTEND, FREEBUSY{values replying)
    DTSTAMP         MUST
    DTSTART         MUST
    DTEND           MUST
    FREEBUSY        MUST (values MUST all be of the same data
                        type. Multiple instances are allowed.
                        Multiple instances MUST be sorted in
                        ascending order. Values MAY NOT overlap}, RELATED-TO{refers overlap)
    ORGANIZER       MUST be the request originator's address
    RECURRENCE-ID   MUST only if referring to another
               related VFREEBUSY component}, REQUEST-STATUS, an instance of a
                        recurring calendar component.  Otherwise it
                        must NOT be present.
    UID             MUST

    ATTACH          MAY PROPERTY = COMMENT{comment from attendee to originator of
               request}, CREATED{specifies
    COMMENT         MAY
    CONTACT         MAY
    CREATED         MAY specifies when the busy time data was
               created}, DTSTART{represents
                        created)
    DTSTART         MAY (represents start of interval for busy
                        time data}, DTEND{represents end of
                        interval for busy time data},LAST-MODIFIED{specifies when busy time data
               was last modified}, SEQUENCE{IF EQ 0}, URL{specifies data)
    GEO             MAY
    RELATED-TO      MAY
    REQUEST-STATUS  MAY
    SEQUENCE        MAY be present if non-zero
    URL             MAY (specifies busy time URL} URL)

    CATEGORIES      NOT
    CLASS           NOT
    DESCRIPTION     NOT
    DURATION        NOT
    EXDATE          NOT
    EXRULE          NOT
    FREEBUSY        NOT
    LAST-MODIFIED   NOT
    PRIORITY        NOT
    RDATE           NOT
    RESOURCES       NOT
    RRULE           NOT
    SEQUENCE        NOT
    STATUS          NOT
    SUMMARY         NOT
    TRANSP          NOT PROPERTY = DURATION, SEQUENCE)
     MAY COMPONENT =

VTIMEZONE (           MUST PROPERTY = DTSTART, TZOFFSET
          MAY PROPERTY = COMMENT, DAYLIGHT, (RDATE / RRULE), TZNAME
          NOT PROPERTY CREATED)
     MAY COMPONENT = be present if any date/time refers to a


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                        timezone

X-TOKENS (ANY)
     NOT COMPONENT =            MAY
VEVENT              NOT COMPONENT =
VTODO               NOT COMPONENT =
VJOURNAL            NOT COMPONENT =
VALARM
     )


3.3              NOT



3.4 Methods For VTODO Component Components

This section defines the property set for the methods that are
applicable to the "VTODO" calendar component . component. Each of the methods is
defined using a grammar restriction table that specifies the property
constraints that define the particular method.

The following summarizes the methods that are defined for the "VTODO"
calendar component . component.


+================+==================================================+


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Internet Draft                   iTIP                 November 21, 1997
| Method         |  Description                                     |
|================+==================================================|
| PUBLISH        | Post notification of a VTODO. Used primarily as  |
|                | a method of advertising the existence of a VTODO.|
|                |                                                  |
| REQUEST        | Assign a VTODO. This is an explicit assignment to|
|                | one or more Calendar Users.VTODO Users. The REQUEST method   |
|                | is also used to update or change an existing     |
|                | VTODO. Clients that cannot handle REQUEST MAY    |
|                | degrade the method to view treat it as a PUBLISH.     |
|                |                                                  |
| REPLY          | Reply to a VTODO request. Attendees MAYset MAY set      |
|                | status ATTSTAT to ACCEPTED, DECLINED, TENTATIVE,        |
|                | DELEGATED, PARTIAL, and COMPLETED.               |
|                |                                                  |
| ADD            | Add one or more instances to an existing to-do.  |
|                |                                                  |
| CANCEL         | Cancel one or more instances of an existing VTODO assignment.      |
|                | to-do.                                           |
|                |                                                  |
| REFRESH        | A request sent to a VTODO "Organizer" asking for |
|                | the latest version of a VTODO.                   |
|                |                                                  |
| COUNTER        | Counter a REQUEST with an alternative proposal.  |
|                |                                                  |
| DECLINECOUNTER | Decline a counter proposal by an attendee. "Attendee."     |
+================+==================================================+


3.3.1







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3.4.1     PUBLISH

The "PUBLISH" method in a "VTODO" calendar component has no reply
   response associated with it. Instead, it
response. It is simply a posting of an iCalendar object that MAY be maybe added
to a calendar by a "Calendar User". It requires and accepts no responses to the "Organizer". It's Its expected usage is for
encapsulating an arbitrary "VTODO" calendar component as an iCalendar
object. The "Organizer" MAY subsequently update (with another "PUBLISH" method)
method), add instances to (win an "ADD" method), or cancel (with a
"CANCEL" method) a previously published "VTODO" calendar component . component.

This method type is an iCalendar object that conforms to the following
property constraints:

     (DESCRIPTION "VTODO - Publish" COMPONENT "VTODO"


Component/Property  Presence
------------------- ----------------------------------------------
PRODID               MUST
VERSION              MUST be "2.0"
METHOD "PUBLISH               MUST COMPONENT = CALPROPS (
          MUST PROPERTY = PRODID, VERSION{"2.0"}, METHOD{"PUBLISH"}) be "PUBLISH"
VTODO                MUST COMPONENT = VTODO(
    DTSTAMP          MUST
    DTSTART          MUST
    ORGANIZER        MUST
    RECURRENCE-ID    MUST only if referring to an instance of a
                         recurring calendar component.  Otherwise it
                         must NOT be present.
    SEQUENCE         MUST PROPERTY = ATTENDEE{only Owner and Organizer be present if not 0, may be present if
               different}, DESCRIPTION{MAYBE NULL}, DTSTAMP, DTSTART,
               PRIORITY, SEQUENCE{IF NE 0}, 0
    SUMMARY          MUST; may be null.
    UID              MUST

    ATTENDEE         MAY PROPERTY = ATTACH, ATTENDEE{other than ROLE=OWNER |
               ORGANIZER}, CATEGORIES, CLASS, COMMENT, CREATED, DUE,
               EXDATE, EXRULE, GEO, LAST-MODIFIED, LOCATION,PERCENT-
               COMPLETE, RELATED-TO, RDATE, RECURRENCE-ID, RESOURCES,
               RRULE, SEQUENCE{IF EQ 0}, STATUS{TENTATIVE/CONFIRMED
               /CANCELLED}, SUMMARY{MAYBE NULL}, URL
          NOT PROPERTY = REQUEST-STATUS)
    ATTACH           MAY COMPONENT = VTIMEZONE (
          MUST PROPERTY = DTSTART, TZOFFSET
    CATEGORIES       MAY
    CLASS            MAY
    COMMENT          MAY
    CONTACT          MAY
    CREATED          MAY
    DESCRIPTION      MAY be present and MAY be NULL
    DURATION         MAY
    DTEND            MAY
    EXDATE           MAY
    EXRULE           MAY
    GEO              MAY
    LAST-MODIFIED    MAY
    LOCATION         MAY
    PERCENT-COMPLETE MAY
    PRIORITY         MAY
    RELATED-TO       MAY
    RDATE            MAY
    RESOURCES        MAY
    RRULE            MAY
    STATUS           MAY be one of COMPLETED/NEEDS ACTION/IN-PROCESS
    TRANSP           MAY
    URL              MAY PROPERTY = COMMENT, DAYLIGHT, (RDATE / RRULE), TZNAME
          NOT PROPERTY = CREATED)


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     MAY COMPONENT = VALARM (
          MUST PROPERTY = CATEGORIES, DSTART, DURATION, REPEAT
          MAY PROPERTY = ATTACH, DESCRIPTION, SUMMARY
     NOT PROPERTY =  COMMENT, CREATED, LAST-MODIFIED, RELATED-TO, URL)
     MAY COMPONENT = X-TOKENS (ANY)
     NOT COMPONENT =                       March 13, 1998



VEVENT               NOT COMPONENT =
VJOURNAL             NOT COMPONENT =
VTIMEZONE            MUST be present if any date/time refers to a
                        timezone
VALARM               MAY
VFREEBUSY
     )

3.3.2            NOT
X-TOKENS             MAY


3.4.2     REQUEST

The "REQUEST" method in a "VTODO" calendar component provides the
following scheduling functions:

. Assign a to-do to one or more "Calendar Users";
. Reschedule an existing to-do;
. Update the details of an existing to-do, without rescheduling it;
. Update the completion status of "Attendees" of an existing to-
        do, to-do,
  without rescheduling it;
. Reconfirm an existing to-do, without rescheduling it;
. Delegate/reassign an existing to-do to another "Calendar User".


The assigned "Calendar Users" are identified in the "VTODO" calendar
component by individual "ATTENDEE;ROLE=ATTENDEE" "ATTENDEE;ROLE=REQ-PARTICIPANT" property value
sequences.

The originator of a "REQUEST" is the "Organizer" of the to-do. The
recipient of a "REQUEST" is the "Calendar User" assigned the to-do,
   called the Attendee. to-do-the
"Attendee". The "Attendee" uses the "REPLY" method to convey their
acceptance and completion status to the "Organizer" of the "REQUEST".

The "UID" "UID", "SEQUENCE", and "SEQUENCE" "DTSTAMP" properties are used to distinguish
the various uses of the "REQUEST" method. If the "UID" property value in
the "REQUEST" is not found on the recipient's calendar, then the
"REQUEST" is for a new to-do. If the "UID" property value is found on
the recipient's calendar, then the "REQUEST" is for either a rescheduling, an
update, or a reconfirm of the "VTODO" calendar object.

If the "Organizer" of the "REQUEST" method is not authorized to make a
to-do request on the "Attendee's" calendar system, then an exception is
returned in the "REQUEST-STATUS" property of a subsequent "REPLY"
method, but no scheduling action is performed.




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This method type is an iCalendar object that conforms to the following
property constraints:

     (DESCRIPTION "VTODO - Request" COMPONENT "VTODO"


Component/Property  Presence
------------------- ----------------------------------------------
PRODID                MUST
VERSION               MUST be "2.0"
METHOD                MUST be "REQUEST"


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VTODO                 MUST COMPONENT = CALPROPS (
          MUST PROPERTY = PRODID, VERSION{"2.0"}, METHOD{"REQUEST"})
    ATTENDEE          MUST COMPONENT = VTODO(
    DTSTAMP           MUST PROPERTY = ATTENDEE{For Owner and Organizer
    DTSTART           MUST
    ORGANIZER         MUST
    RECURRENCE-ID     MUST only if different
               and each Attendee},DESCRIPTION{MAYBE NULL}, DTSTAMP,
               DTSTART, PRIORITY, SEQUENCE{IF NE 0}, referring to an instance of a
                          recurring calendar component.  Otherwise it
                          must NOT be present.
    SEQUENCE          MUST be present if not 0, may be present if 0
    SUMMARY           MUST; may be null.
    UID               MUST
    ATTACH            MAY PROPERTY = ATTACH, CATEGORIES, CLASS, COMMENT,
               CREATED, DUE, EXDATE, EXRULE, GEO, LAST-MODIFIED,
               LOCATION, PERCENT-COMPLETE, RELATED-TO, RDATE,
               RECURRENCE-ID, RESOURCES, RRULE, SEQUENCE{IF EQ 0},
               STATUS{TENTATIVE/CONFIRMED/CANCELLED}, SUMMARY{MAYBE
               NULL}, URL
          NOT PROPERTY = REQUEST-STATUS)
    CATEGORIES        MAY COMPONENT = VTIMEZONE (
          MUST PROPERTY = DTSTART, TZOFFSET
    CLASS             MAY
    COMMENT           MAY
    CONTACT           MAY
    CREATED           MAY
    DESCRIPTION       MAY be present and MAY be NULL
    DURATION          MAY
    DTEND             MAY
    EXDATE            MAY
    EXRULE            MAY
    GEO               MAY
    LAST-MODIFIED     MAY
    LOCATION          MAY
    PERCENT-COMPLETE  MAY
    PRIORITY          MAY
    RELATED-TO        MAY
    RDATE             MAY
    RESOURCES         MAY
    RRULE             MAY PROPERTY = COMMENT, DAYLIGHT, (RDATE / RRULE), TZNAME
          NOT PROPERTY = CREATED)
    STATUS            MAY COMPONENT = VALARM (
          MUST PROPERTY = CATEGORIES, DSTART, DURATION, REPEAT be one of COMPLETED/NEEDS ACTION/IN-PROCESS
    TRANSP            MAY PROPERTY = ATTACH, DESCRIPTION, SUMMARY
          NOT PROPERTY =  COMMENT, CREATED, LAST-MODIFIED, RELATED-TO,
               URL)
    URL               MAY COMPONENT = X-TOKENS (ANY)
     NOT COMPONENT =

VEVENT                NOT COMPONENT =
VJOURNAL              NOT COMPONENT =
VTIMEZONE             MUST be present if any date/time refers to a
                          timezone
VALARM                MAY
VFREEBUSY
     )


3.3.2.1             NOT
X-TOKENS              MAY


3.4.2.1   REQUEST for Rescheduling a VTODO

The "REQUEST" method MAY may be used to reschedule a "VTODO" calendar
   component .

   A rescheduled
component.

Rescheduling a "VTODO" calendar component involves a change to the
existing "VTODO" calendar component in terms of it's its start or due time or
recurrence intervals and possibly the description. If the recipient "CUA" CUA
of a "REQUEST" method finds that the "UID" property value already exists
on the calendar, but that the "SEQUENCE" property value in the "REQUEST"


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is greater than the value for the existing VTODO, then the "REQUEST"
method describes a rescheduling of the "VTODO" calendar component.








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3.3.2.2


3.4.2.2   REQUEST for Update or Reconfirmation of a VTODO

The "REQUEST" method MAY may be used to update or reconfirm a "VTODO"
calendar component. Reconfirmation is merely an update of "Attendee"
completion status or overall "VTODO" calendar component status.

An update to an existing "VTODO" calendar component does not involve
changes to the start or due time or recurrence intervals, nor generally
to the description for the "VTODO" calendar component. If the recipient "CUA"
CUA of a "REQUEST" method finds that the "UID" property value already
exists on the calendar and that the "SEQUENCE" property value in the
"REQUEST" is the same as the value for the existing event, then the
"REQUEST" method describes an update of the "VTODO" calendar component
details, but no not a rescheduling of the "VTODO" calendar component.

The update "REQUEST" is the appropriate response to a "REFRESH" method
sent from an "Attendee" to the "Organizer" of a "VTODO" calendar
component.

Unsolicited "REQUEST" methods MAY also be sent by the "Organizer" of a
"VTODO" calendar component. The unsolicited "REQUEST" methods MAY
   be are used
to either update the details of the VTODO, without "VTODO" (without rescheduling it or to update
updating the completion status of "Attendees" "Attendees") or the "VTODO" calendar
component itself (i.e., reconfirm the VTODO).

3.3.2.3 "VTODO").


3.4.2.3   REQUEST for Delegating a VTODO

The "REQUEST" method MAY be is also used to delegate or reassign ownership of a
"VTODO" calendar component to another "Calendar User". The
   "REQUEST" method is For example, it
may be used to delegate the an "Attendee's" role (i.e. "
   "Organizer", "chair", or "Attendee")
"participant") for a "VTODO" calendar component. The "REQUEST" method is
sent by one of the "Attendees" of an existing "VTODO" calendar component request
to some other individual. In order
   to avoid scheduling loops, the method MUST NOT be sent from an
   "Attendee" back to the "Organizer" of the "VTODO" calendar component. An "Attendee" of a "VTODO" calendar component MAY
MUST NOT delegate to the "Organizer" of the event.

For the purposes of this description, the "Attendee" delegating the
"VTODO" calendar component is referred to as the "delegator". "Delegator". The
"Attendee" receiving the delegation request is referred to as the
   "delegatee".
"Delegate".

The "delegator" "Delegator" of a "VTODO" calendar component MUST forward the
existing "REQUEST" method for a "VTODO" calendar component to the
   "delegatee".
"Delegate". The "VTODO" calendar component description MUST include the "delegator's"
"Delegator's" up-to-date "VTODO" calendar component definition. The
"REQUEST" method MUST also include an "ATTENDEE" property with the
calendar address of the "delegatee". "Delegate". The "delegator" "Delegator" MUST also send a
"REPLY" method back to the "Organizer" with the "delegator's" "Delegator's" "Attendee"
property "STATUS" "attstat" parameter value set to DELEGATED. "DELEGATED". In


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the "delegatee". "Delegate". A response to the delegation "REQUEST" is sent from the "delegatee"
"Delegate" to the "Organizer" and optionally, to the "delegator". "Delegator". The
"REPLY" method from the
   "delegatee" "Delegate" SHOULD include the "ATTENDEE"
property with their calendar address and the "DELEGATED-FROM" "delegated-from" parameter
with the value of the "delegator's"calendar "Delegator's" calendar address.

The delegation "REQUEST" method MUST assign the values of a value for the "RSVP"
   and "EXPECT"
property parameters parameter associated with the "delegator's" "Delegator's" "Attendee" property
to that of the "delegatee's" "Attendee" "Delegate's" "ATTENDEE" property. For example if the "delegator's" "Attendee"
"Delegator's" "ATTENDEE" property specifies
   "RSVP=TRUE;EXPECT=REQUEST", "RSVP=TRUE", then the "delegatee's" "Attendee"
"Delegate's" "ATTENDEE" property MUST specify "RSVP=TRUE;EXPECT=REQUEST".

3.3.2.4 "RSVP=TRUE".


3.4.2.4   REQUEST Forwarded To An Uninvited Calendar User

An "Attendee" assigned a "VTODO" calendar component MAY also may assign the
"VTODO" calendar component to another new "Calendar User", not
previously associated with the "VTODO" calendar component. The current
"Attendee" assigned the "VTODO" calendar component accomplishes this
scheduling action by forwarding the original "REQUEST" method to the new "Calendar User".

   An "Organizer" of a "VTODO" calendar component MAY also request an
   updated completion status from one of the "Attendees". This is
   achieved by the "Organizer" sending a "REQUEST" method to the
   "Attendee" with the "ATTENDEE;RSVP=TRUE" property sequence. The
   "SEQUENCE" property for the "VTODO" calendar component is not changed
   from its previous value. A recipient will determine that the only
   change in the "REQUEST" is that their "RSVP" property parameter
   indicates a request for an updated status. The recipient SHOULD
   respond with a "REPLY" method indicating their current status with
   respect to the "REQUEST".

3.3.2.5 new
"Calendar User".


3.4.2.5   REQUEST Updated Attendee Status

An "Organizer" of a to-do MAY also "VTODO" may request an updated status from one
   of the or
more "Attendees". This is achieved by the The "Organizer" sending sends a "REQUEST" method to the
"Attendee" with the "ATTENDEE;RSVP=TRUE" property sequence. The
"SEQUENCE" property for the to-do "VTODO" is not changed from its previous
value. A recipient will determine determines that the only change in the "REQUEST" is
that their "RSVP" property parameter indicates a request for an updated
status. The recipient SHOULD respond with a "REPLY" method indicating
their current status with respect to the "REQUEST".

   This capability MAY also be achieved by the "Organizer" sending the
   "REFRESH" method to the "Attendees".





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3.3.3


3.4.3     REPLY

The "REPLY" method in a "VTODO" calendar component is used to respond
(e.g., accept or decline) to a request or to reply to a delegation
request. It is also used by an "Attendee" to update their completion
status. When used to provide a delegation response, the "delegator" "Delegator"
SHOULD include the calendar address of the "delegatee" "Delegate" in the
   "DELEGATED-TO" "delegated-
to" parameter of the "delegator's" "Delegator's" "ATTENDEE" property. The "delegatee" "Delegate"
SHOULD include the calendar address of the
   "delegator" "Delegator" on the "DELEGATED-FROM"
"delegated-from" parameter of the "delegatee's" "Delegate's" "ATTENDEE" property.

The "REPLY" method MAY also be used to respond to an unsuccessful
"VTODO" calendar component "REQUEST" method. Depending on the
   "REQUEST-STATUS" "REQUEST-
STATUS" value, no scheduling action MAY may have been performed.

The "Organizer" of a "VTODO" calendar component MAY receive a "REPLY"
method from a "Calendar User" not in the original "REQUEST". For
example, a "REPLY" method MAY be received from a "delegatee" "Delegate" of a "VTODO"
calendar component. In addition, the "REPLY" method MAY be received from


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an unknown "Calendar User"; User", having been forwarded the "REQUEST"
   from by an
original "Attendee" assigned of the "VTODO" calendar component. This uninvited
"Attendee" MAY be accepted, or the "Organizer" MAY cancel the "VTODO"
calendar component for the uninvited uninvited "Attendee" by sending them a
"CANCEL" method.

This method type is an iCalendar object that conforms to the following
property constraints:


Component/Property   Presence
-------------------  ---------------------------------------------
PRODID               MUST
VERSION              MUST be "2.0"
METHOD               MUST be "REPLY"
VTODO                MUST
    ATTENDEE         MUST
    UID              MUST must be the address of the replying attendee
    DTSTAMP          MUST
    ORGANIZER        MUST
    RECURRENCE-ID    MUST only if referring to an instance of a
                          Recurring calendar component. Otherwise it
                          Must NOT be present
    SEQUENCE         MUST

    COMMENT          MAY
    PERCENT-COMPLETE MAY
    REQUEST-STATUS   MAY

    DTSTART          NOT
    CREATED          NOT
    DESCRIPTION      NOT
    PRIORITY         NOT
    CLASS            NOT
    CATEGORIES       NOT
    CONTACT          NOT
    CREATED          NOT
    DTEND            NOT
    GEO              NOT
    LAST-MODIFIED    NOT
    LOCATION         NOT
    RDATE            NOT
    RRULE            NOT
    RELATED-TO       NOT
    RESOURCE         NOT
    STATUS           NOT
    TRANSP           NOT
    URL              NOT
VTIMEZONE            MUST be present if any date/time refers to a
                         timezone
VALARM               NOT
VEVENT               NOT
VFREEBUSY            NOT
X-TOKENS             NOT


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3.4.4     ADD

The "ADD" method in a "VTODO" calendar component is used to add one or
more instances to an existing to-do.

If the "UID" property value in the "ADD" is not found on the recipient's
calendar, then the recipient SHOULD send a "REFRESH" to the "Organizer"
in order to be updated with the latest version of the "VTODO". If an
"Attendee" by
   sending them implementation does not support the "ADD" method it should
respond with a "CANCEL" method. "REQUEST-STATUS" value of 5.3 and ask for a "REFRESH".

This method type is an iCalendar object that conforms to the following
property constraints:

     (DESCRIPTION "VTODO - Reply" COMPONENT "VTODO"

Component/Property  Presence
------------------- ----------------------------------------------
PRODID                MUST
VERSION               MUST be "2.0"
METHOD "REPLY"                MUST COMPONENT = CALPROPS (
          MUST PROPERTY = PRODID, VERSION{"2.0"}, METHOD{"REPLY"}) be "ADD"
VTODO                 MUST COMPONENT = VTODO(
    DTSTAMP           MUST
    DTSTART           MUST
    ORGANIZER         MUST
    SEQUENCE          MUST PROPERTY = ATTENDEE{MUST be address greater than 0
    SUMMARY           MUST; may be null.
    UID               MUST match that of ATTENDEE
               replying}, DTSTAMP, SEQUENCE{IF NE 0}, UID{UID
               associated with the original REQUEST}
          MAY PROPERTY = COMMENT{provides comment from to-do

    ATTENDEE to
               "Organizer"}, EXDATE, EXRULE, RECURRENCE-ID, REQUEST-
               STATUS, PERCENT-COMPLETE, SEQUENCE{IF EQ 0}, SUMMARY
               {MAYBE NULL},          MAY
    ATTACH            MAY
    CATEGORIES        MAY
    CLASS             MAY
    COMMENT           MAY
    CONTACT           MAY
    CREATED           MAY
    DESCRIPTION       MAY be present and MAY be NULL
    DTEND             MAY
    DURATION          MAY
    EXDATE            MAY
    EXRULE            MAY
    GEO               MAY
    LAST-MODIFIED     MAY
    LOCATION          MAY
    PERCENT-COMPLETE  MAY
    PRIORITY          MAY
    RELATED-TO        MAY
    RDATE             MAY
    RESOURCES         MAY
    RRULE             MAY
    STATUS           MAY be one of COMPLETED/NEEDS ACTION/IN-PROCESS
    TRANSP            MAY
    URL
          NOT PROPERTY = ATTACH, CATEGORIES, CLASS, CREATED,
               DESCRIPTION, DTSTART, DUE, GEO, LAST-MODIFIED, PRIORITY,
               RELATED-TO, RESOURCES, RDATE, RRULE, STATUS, SUMMARY,
               TRANSP, URL)               MAY COMPONENT = X-TOKENS (ANY)



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    RECURRENCE-ID     NOT
    REQUEST-STATUS    NOT COMPONENT =

VEVENT                NOT COMPONENT =
VJOURNAL              NOT COMPONENT = VFREEBUSY
     NOT COMPONENT =
VTIMEZONE
     NOT COMPONENT =             MUST be present if any date/time refers to a
                          timezone
VALARM
     )



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3.3.4
VFREEBUSY             NOT
X-TOKENS              MAY


3.4.5     CANCEL

The "CANCEL" method in a "VTODO" calendar component is used to send a
cancellation notice of an existing "VTODO" calendar request request to the
"Attendees". The message is sent by the "Organizer" of a "VTODO"
calendar component to the "Attendees" of the "VTODO" calendar component.
For a recurring "VTODO" calendar component, either the whole "VTODO"
calendar component or instances of a "VTODO" calendar component MAY may be
cancelled. To cancel the complete range of a recurring "VTODO" calendar
component, the "UID" property value for the "VTODO" calendar component
MUST be specified and a "RECURRENCE-ID" MUST NOT be specified in the
"CANCEL" method. In order to cancel an individual instance of a
recurring "VTODO" calendar component, the "RECURRENCE-ID" property value
for the "VTODO" calendar component MUST be specified in the "CANCEL"
method. In order to cancel

There are two options for canceling a sequence of instances of a
recurring "VTODO" calendar component, either component:

(a)    the "RECURRENCE-ID" property for
   the first an instance in the sequence MUST be
  specified with the "RANGE" property parameter value of THISANDPRIOR or THISANDFUTURE;
  (or THISANDFUTURE)  to indicate cancellation of the specified "VTODO"
  calendar component and all instances before and after the first instance, respectively. Lastly, (or after); or

(b)    individual recurrence instances may be cancelled by specifying
  multiple "RECURRENCE-ID" properties corresponding to the instances to
  be cancelled.

This method type is an iCalendar object that conforms to the following
property constraints:


Component/Property   Presence
-------------------  ---------------------------------------------
PRODID               MUST
VERSION              MUST be "2.0"
METHOD               MUST be "CANCEL"
VTODO                MUST
    UID              MUST must echo original UID
    DTSTAMP          MUST
    ORGANIZER        MUST
    SEQUENCE         MUST


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    RECURRENCE-ID    MUST only if referring to one or more instances
                          of a recurring calendar component. Otherwise
                          it MUST NOT be present
    COMMENT          MAY
    ATTENDEE         MAY
    DTSTART          MAY
    CREATED          MAY
    DESCRIPTION      MAY
    ORGANIZER        MAY
    PRIORITY         MAY
    CLASS            MAY
    CATEGORIES       MAY
    CONTACT          MAY
    CREATED          MAY
    DTEND            MAY
    GEO              MAY
    LAST-MODIFIED    MAY
    LOCATION         MAY
    PERCENT-COMPLETE MAY
    PRIORITY         MAY
    RDATE            MAY
    RRULE            MAY
    RELATED-TO       MAY
    REQUEST-STATUS   MAY
    RESOURCE         MAY
    STATUS           MAY If present it must be cancelled by specifying multiple
   "RECURRENCE-ID" properties corresponding to the instances set to "CANCELLED".
                         MUST NOT be
   cancelled.

   This method type used if purpose is an iCalendar object that conforms to remove
                         "ATTENDEES" rather than cancel the
   following property constraints:

     (DESCRIPTION "VTODO - Cancel" COMPONENT "VTODO" METHOD "CANCEL"

     MUST COMPONENT = CALPROPS (
          MUST PROPERTY = PRODID, VERSION{"2.0"}, METHOD{"CANCEL"})
     MUST COMPONENT = VTODO(
          MUST PROPERTY = DTSTAMP, SEQUENCE{IF NE 0}, UID{UID
               associated with original REQUEST} entire
                         VTODO.
    TRANSP           MAY PROPERTY = COMMENT{provides comment from "Organizer"
    URL              MAY

VTIMEZONE             MUST be present if any date/time refers to
               ATTENDEE}, EXDATE, EXRULE, RECURRENCE-ID, SEQUENCE{IF EQ
               0}, STATUS{CANCELLED}
          NOT PROPERTY = ATTACH, ATTENDEE, CATEGORIES, CLASS, CREATED,
               DESCRIPTION, DTSTART, DUE, GEO, LAST-MODIFIED, PRIORITY,
               RDATE, RELATED-TO, RESOURCES, REQUEST-STATUS, RRULE,
               SUMMARY, TRANSP, URL) a
                          timezone
VALARM               MAY COMPONENT = X-TOKENS (ANY)
     NOT COMPONENT =
VEVENT
     NOT COMPONENT = VJOURNAL
     NOT COMPONENT =               MAY
VFREEBUSY
     NOT COMPONENT = VTIMEZONE
     NOT COMPONENT = VALARM
     )







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3.3.5
X-TOKENS             MAY


3.4.6     REFRESH

The "REFRESH" method in a "VTODO" calendar component is used by
"Attendees" of an existing "VTODO" calendar component to request an
updated description from the "Organizer" of the "VTODO" calendar
component. The "Organizer" of the "VTODO" calendar component MAY also use
this method to request an updated status from the "Attendees". The
"REFRESH" method MUST specify the "UID" property corresponding to the
"VTODO" calendar component needing update.

A refresh of a recurrence instance of a "VTODO" calendar component
   MAY may
be requested by specifying the "RECURRENCE-ID" property corresponding to
the associated "VTODO" calendar component. The "Organizer" MUST respond responds with
the latest description and rendition of the "VTODO" calendar component.


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This method is intended to facilitate machine processing of requests for
updates to a "VTODO" calendar component.

This method type is an iCalendar object that conforms to the following
property constraints:

     (DESCRIPTION "VTODO - Refresh" COMPONENT "VTODO"


Component/Property   Presence
-------------------  ---------------------------------------------
PRODID               MUST
VERSION              MUST be "2.0"
METHOD               MUST be "REFRESH"
VTODO                MUST COMPONENT = CALPROPS (
          MUST PROPERTY = PRODID, VERSION{"2.0"}, METHOD{"REFRESH"})
    ATTENDEE         MUST COMPONENT = VTODO(
    DTSTAMP          MUST PROPERTY = ATTENDEE{address of requestor}, DTSTAMP,
               SEQUENCE{IF NE 0}, UID{UID associated with
    RECURRENCE-ID    MUST only if referring to an instance of a
                          Recurring calendar component. Otherwise it
                          MUST NOT be present
    UID              MUST echo original
               REQUEST} UID
    COMMENT          MAY
    REQUEST-STATUS   MAY
    DTSTART          MAY
    CREATED          MAY
    DESCRIPTION      MAY
    PRIORITY         MAY
    CLASS            MAY
    CATEGORIES       MAY
    CONTACT          MAY
    CREATED          MAY
    DTEND            MAY
    GEO              MAY
    LAST-MODIFIED    MAY
    PERCENT-COMPLETE MAY
    ORGANIZER        MAY
    PRIORITY         MAY
    LOCATION         MAY
    RDATE            MAY
    RRULE            MAY
    RELATED-TO       MAY
    RESOURCE         MAY
    SEQUENCE         MAY
    STATUS           MAY
    TRANSP           MAY PROPERTY = COMMENT{provides comment from
               ATTENDEE
    URL              MAY
VTIMEZONE            MUST be present if any date/time refers to "Organizer"}, RECURRENCE-ID, SEQUENCE{IF EQ
               0}
          NOT PROPERTY = ATTACH, CATEGORIES, CLASS, CREATED,
               DESCRIPTION, DTSTART, DUE, EXDATE, EXRULE, GEO, LAST-
               MODIFIED, PRIORITY, RDATE,RELATED-TO, RESOURCES,
               REQUEST-STATUS, RRULE,SUMMARY, STATUS, TRANSP, URL) a
                         timezone
VALARM               MAY COMPONENT = X-TOKENS (ANY)
     NOT COMPONENT =
VEVENT
     NOT COMPONENT = VJOURNAL
     NOT COMPONENT =               MAY
VFREEBUSY
     NOT COMPONENT = VTIMEZONE
     NOT COMPONENT = VALARM
     )

3.3.6            MAY
X-TOKENS             MAY






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3.4.7     COUNTER

The "COUNTER" method in a "VTODO" calendar component is used by an
"Attendee" of an existing "VTODO" calendar component to submit to the
"Organizer" a counter proposal for the "VTODO" calendar component. The
"Attendee" MUST send sends the message to the "Organizer" of the "VTODO" calendar
component.




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The counter proposal is an iCalendar object consisting of a "VTODO"
calendar component describing the complete description of the alternate
"VTODO" calendar component.

The "Organizer" rejects the counter proposal by sending the "Attendee" a
"DECLINE-COUNTER" method. The "Organizer" accepts the counter proposal
by sending all of the "Attendees" of the "VTODO" calendar component a
"REQUEST" method rescheduling the "VTODO" calendar component. In the later
latter case, the "Organizer" SHOULD reset the individual "RSVP" property
parameter values to TRUE on each "ATTENDEE" property; in order to force
a response by the "Attendees".

This method type is an iCalendar object that conforms to the following
property constraints:

     (DESCRIPTION "VTODO- Request" COMPONENT "VTODO"


Component/Property  Presence
------------------- ----------------------------------------------
PRODID               MUST
VERSION              MUST be "2.0"
METHOD "REQUEST"               MUST COMPONENT = CALPROPS (
          MUST PROPERTY = PRODID, VERSION{"2.0"}, METHOD{"REQUEST"}) be "COUNTER"
VTODO                MUST COMPONENT = VTODO(
    DTSTAMP          MUST PROPERTY = ATTENDEE{For Owner and Orginator if different
               and Attendees}, DESCRIPTION{MAYBE NULL}, DTSTAMP,
               DTSTART, PRIORITY, SEQUENCE{IF NE 0}, UID
    DTSTART          MAY PROPERTY = ATTACH, CATEGORIES, CLASS, COMMENT,CREATED,
               DUE, EXDATE, EXRULE, GEO, LAST-MODIFIED,
               LOCATION,RELATED-TO, RDATE, RECURRENCE-ID, RESOURCES,
               RRULE, SEQUENCE{IF EQ 0}, STATUS{TENTATIVE/CONFIRMED
               /CANCELLED}, SUMMARY{MAYBE NULL}, URL
    ORGANIZER        MUST
    RECURRENCE-ID    MUST only if referring to an instance of a
                         recurring calendar component.  Otherwise it
                         MUST NOT PROPERTY = REQUEST-STATUS)
     MAY COMPONENT = VTIMEZONE ( be present.
    SEQUENCE         MUST PROPERTY = DTSTART, TZOFFSET
          MAY PROPERTY = COMMENT, DAYLIGHT, (RDATE / RRULE), TZNAME be present if NOT PROPERTY = CREATED) 0, MAY COMPONENT = VALARM ( be present if 0
    SUMMARY          MUST PROPERTY = CATEGORIES, DSTART, DURATION, REPEAT be present; MAY PROPERTY = ATTACH, DESCRIPTION, SUMMARY
     NOT PROPERTY =  COMMENT, CREATED, LAST-MODIFIED, RELATED-TO, URL) be NULL
    UID              MUST

    ATTENDEE         MAY COMPONENT = X-TOKENS (ANY)
     NOT COMPONENT = VEVENT
     NOT COMPONENT = VJOURNAL
     NOT COMPONENT = VFREEBUSY
     )

3.3.7     DECLINECOUNTER


   The "DECLINE-COUNTER" method in a "VTODO" calendar component is used
   by an "Organizer" of "VTODO" calendar component to reject a counter
   proposal offered by
    ATTACH           MAY
    CATEGORIES       MAY
    CLASS            MAY
    COMMENT          MAY
    CONTACT          MAY
    CREATED          MAY
    DESCRIPTION      MAY be present; MAY be NULL
    DURATION         MAY
    DTEND            MAY
    EXDATE           MAY
    EXRULE           MAY
    GEO              MAY
    LAST-MODIFIED    MAY


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    LOCATION         MAY
    PERCENT-COMPLETE MAY
    PRIORITY         MAY
    RELATED-TO       MAY
    RDATE            MAY
    RESOURCES        MAY
    RRULE            MAY
    STATUS           MAY be one of the "Attendees". The "Organizer" COMPLETED/NEEDS ACTION/IN-PROCESS
    TRANSP           MAY
    URL              MAY
VEVENT               MAY
VJOURNAL             MAY
VTIMEZONE            MUST send
   the message to the "Attendee" that sent the "COUNTER" method be present if any date/time refers to the
   "Organizer".





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VALARM               MAY
VFREEBUSY            MAY
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3.4.8     DECLINECOUNTER

The counter proposal is an iCalendar object consisting of "DECLINE-COUNTER" method in a "VTODO" calendar component describing the complete description is used by
an "Organizer" of the
   alternate "VTODO" calendar component.

   The "Organizer" rejects the counter proposal by sending the
   "Attendee" component to reject a "DECLINE-COUNTER" method. The "Organizer" accepts the counter
proposal offered by sending all of the "Attendees" one of the "VTODO"
   calendar component a "REQUEST" method rescheduling the "VTODO"
   calendar component. Since this is a rescheduled "VTODO", the
   "SEQUENCE" property value will be incremented. In the later case, the "Attendees". The "Organizer" SHOULD reset sends the individual "RSVP" property parameter
   values
message to TRUE on all of the "ATTENDEE" properties in order "Attendee" that sent the "COUNTER" method to force
   a response by the "Attendees".
"Organizer".

This method type is an iCalendar object that conforms to the following
property constraints:

     (DESCRIPTION "VTODO - Cancel" COMPONENT "VTODO"

Component/Property   Presence
-------------------  ---------------------------------------------
PRODID               MUST
VERSION              MUST be "2.0"

METHOD               MUST be "DECLINECOUNTER"

VTODO                MUST COMPONENT = CALPROPS (
          MUST PROPERTY = PRODID, VERSION{"2.0"}, METHOD
               {"DECLINECOUNTER"})
    ATTENDEE         MUST COMPONENT = VTODO( for all attendees
    UID              MUST PROPERTY = DTSTAMP, SEQUENCE{IF NE 0}, UID{same must echo original UID
               specified In Original REQUEST and subsequent COUNTER}
    DTSTAMP          MUST
    SEQUENCE         MUST
    RECURRENCE-ID    MUST only if referring to an instance of a
                          recurring calendar component.  Otherwise it
                          MUST NOT be present.

    COMMENT          MAY PROPERTY = COMMENT{provides comment from "Organizer"
    PERCENT-COMPLETE MAY
    REQUEST-STATUS   MAY
    DTSTART          MAY
    CREATED          MAY
    DESCRIPTION      MAY
    ORGANIZER        MAY
    PRIORITY         MAY


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    CLASS            MAY
    CATEGORIES       MAY
    CONTACT          MAY
    CREATED          MAY
    DTEND            MAY
    GEO              MAY
    LAST-MODIFIED    MAY
    LOCATION         MAY
    RDATE            MAY
    RRULE            MAY
    RELATED-TO       MAY
    RESOURCE         MAY
    STATUS           MAY be one of COMPLETED/NEEDS ACTION/IN-PROCESS
    TRANSP           MAY
    URL              MAY

VTIMEZONE            MUST be present if any date/time refers to
               ATTENDEE}, RECURRENCE-ID, REQUEST-STATUS, SEQUENCE{IF EQ
               0}
          NOT PROPERTY = ATTACH, ATTENDEE, CATEGORIES, CLASS, CREATED,
               DESCRIPTION, DTSTART, DUE, EXDATE, EXRULE, GEO, LAST-
               MODIFIED, PRIORITY, RDATE, RELATED-TO, RESOURCES, RRULE,
               STATUS, SUMMARY, TRANSP, URL) a
                         timezone
VALARM               MAY COMPONENT = X-TOKENS (ANY)
     NOT COMPONENT =
VEVENT
     NOT COMPONENT = VJOURNAL
     NOT COMPONENT =               MAY
VTODO                MAY
VFREEBUSY
     NOT COMPONENT = VTIMEZONE
     NOT COMPONENT = VALARM
     )

3.4            MAY
X-TOKENS             MAY

3.5 Methods For VJOURNAL Component Components

This section defines the property set for the methods that are
applicable to the "VJOURNAL" calendar component. Each of the methods
   is defined using a grammar that clarifies the property constraints
   that define the particular method.

The following summarizes the methods that are defined for the "VJOURNAL"
calendar component.

+================+==================================================+
| Method         |  Description                                     |


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|================+==================================================|
| PUBLISH        | Post a journal entry. Used primarily as a method |
|                | of advertising the existence of a journal entry entry. |
|                |                                                  |
| ADD            | Add one or more instances to an existing journal |
|                | entry.                                           |
|                |                                                  |
| CANCEL         | Cancel one or more instances of an existing journal entry request.      |
| REFRESH                | A request sent journal entry.                                   |
+================+==================================================+


3.5.1     PUBLISH

The "PUBLISH" method in a "VJOURNAL" calendar component has no
associated response. It is simply a posting of an iCalendar object that
may be added to a calendar by a CUA. There is no response to the
"Organizer". The expected usage is for encapsulating an arbitrary
journal entry as an iCalendar object. The "Organizer" for    |
 |                | MAY subsequently



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update (with another "PUBLISH" method) or cancel (with a "CANCEL"
method) a previously published journal entry.

This method type is an iCalendar object that conforms to the latest version following
property constraints:

Component/Property  Presence
------------------- ----------------------------------------------
PRODID               MUST
VERSION              MUST be "2.0"
METHOD               MUST be "PUBLISH"
VJOURNAL             MUST
    DTSTAMP          MUST
    DTSTART          MUST
    ORGANIZER        MUST
    RECURRENCE-ID    MUST only if referring to an instance of a
                         recurring calendar component.  Otherwise it
                         MUST NOT be present.
    SEQUENCE         MUST be present if not 0, MAY be present if 0
    SUMMARY          MUST be present and MAY be NULL
    UID              MUST

    ATTENDEE         MAY
    ATTACH           MAY
    CATEGORIES       MAY
    CLASS            MAY
    COMMENT          MAY
    CONTACT          MAY
    CREATED          MAY
    DESCRIPTION      MAY be present; MAY be NULL.
    DURATION         MAY
    DTEND            MAY
    EXDATE           MAY
    EXRULE           MAY
    GEO              MAY
    LAST-MODIFIED    MAY
    LOCATION         MAY
    PRIORITY         MAY
    RELATED-TO       MAY
    RDATE            MAY
    RESOURCES        MAY
    RRULE            MAY
    STATUS           MAY be one of the journal entry to DRAFT/FINAL/CANCELLED
    TRANSP           MAY
    URL              MAY

VEVENT               MAY
VTODO                MAY
VTIMEZONE            MUST be    |
 |                | resent the requester.                            |
 +================+==================================================+


3.4.1     PUBLISH present if any date/time refers to a
                         timezone
VALARM               MAY
VFREEBUSY            MAY
X-TOKENS             MAY



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3.5.2     ADD

The "PUBLISH" "ADD" method in a "VJOURNAL" calendar component has no reply
   response associated with it. Instead, it is simply a posting of an
   iCalendar object that MAY be added used to a calendar by a "Calendar User"
   agent. It requires and accepts add one
or more instances to an existing "VJOURNAL" entry. There is no responses response
to the "Organizer". The
   expected usage

If the "UID" property value in the "ADD" is for encapsulating an arbitrary journal entry as an
   iCalendar object. The "Organizer" not found on the recipient's
calendar, then the recipient MAY subsequently update (with
   another "PUBLISH" method) or cancel (with a "CANCEL" method) treat the "ADD" as a
   previously published journal entry. "PUBLISH".

This method type is an iCalendar object that conforms to the following
property constraints:

     (DESCRIPTION "Journal - Publish" COMPONENT "VJOURNAL" METHOD
          "PUBLISH

Component/Property  Presence
------------------- ----------------------------------------------
PRODID               MUST COMPONENT = CALPROPS (
          MUST PROPERTY = PRODID, VERSION{"2.0"}, METHOD{"PUBLISH"})
VERSION              MUST COMPONENT = be "2.0"
METHOD               MUST be "ADD"
VJOURNAL (             MUST PROPERTY = DESCRIPTION{MAYBE NULL}, DTSTAMP,
               DTSTART{VALUE=DATE}, SEQUENCE{IF NE 0},
    DTSTAMP          MUST
    DTSTART          MUST
    ORGANIZER        MUST
    SEQUENCE         MUST be greater than 0
    SUMMARY          MUST be present and MAY be NULL
    UID              MUST match that of the original journal

    ATTACH           MAY PROPERTY = ATTACH, ATTENDEE{only ROLE=ORGANIZER and
               OWNER if different}, CATEGORIES, CLASS, COMMENT,
               CREATED, EXDATE, EXRULE, LAST-MODIFIED, RELATED-TO,
               RDATE, RECURRENCE-ID, RRULE, SEQUENCE{IF EQ 0},
               SUMMARY{MAYBE NULL}, URL
          NOT PROPERTY = REQUEST-STATUS)
    CATEGORIES       MAY COMPONENT = VTIMEZONE (
          MUST PROPERTY = DTSTART, TZOFFSET
    CLASS            MAY PROPERTY = COMMENT, DAYLIGHT, (RDATE / RRULE), TZNAME
          NOT PROPERTY = CREATED)
    COMMENT          MAY COMPONENT = X-TOKENS (ANY)
    CONTACT          MAY
    CREATED          MAY
    DESCRIPTION      MAY be present; may be null.
    DURATION         MAY
    DTEND            MAY
    EXDATE           MAY
    EXRULE           MAY
    GEO              MAY
    LAST-MODIFIED    MAY
    LOCATION         MAY
    PRIORITY         MAY
    RELATED-TO       MAY
    RDATE            MAY
    RESOURCES        MAY
    RRULE            MAY
    STATUS           MAY be one of DRAFT/FINAL/CANCELLED
    TRANSP           MAY
    URL              MAY

    ATTENDEE         NOT COMPONENT = VEVENT
    RECURRENCE-ID    NOT COMPONENT =

VEVENT               MAY
VTODO
     NOT COMPONENT = VALARM
     NOT COMPONENT = VFREEBUSY
     )                MAY
VTIMEZONE            MUST be present if any date/time refers to a


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                         timezone
VALARM               MAY
VFREEBUSY            MAY
X-TOKENS             MAY


3.5.3     CANCEL

The "CANCEL" method in a "VJOURNAL" calendar component is used to send a
cancellation notice of an existing journal entry request to
   the "Attendees". entry. The message is sent by
the "Organizer" of a journal
   entry to the "Attendees" of the journal entry. For a recurring journal entry,
either the whole journal entry or instances of a journal entry MAY may be
cancelled. To cancel the complete range of a recurring journal entry,
the "UID" property value for the journal entry MUST be specified and a
"RECURRENCE-ID" property MUST NOT be specified in the "CANCEL" method.
In order to cancel an individual instance of the journal entry, the
"RECURRENCE-ID" property value for the journal entry MUST be specified
in the "CANCEL" method. In order to cancel

There are two options for canceling a sequence of instances in of a
recurring journal entry, "VJOURNAL" calendar component:

(a)    the "RECURRENCE-ID" property for the first
   journal entry an instance in the sequence MUST be
  specified with the "RANGE" property parameter value of THISANDPRIOR or THISANDFUTURE;
  (or THISANDFUTURE)  to indicate cancellation of the journal entry specified "VTODO"
  calendar component and all instances before and after
   the first journal entry instance, respectively. Lastly, (or after); or

(b)    individual recurrence instances MAY may be cancelled by specifying
  multiple "RECURRENCE-ID" properties corresponding to the instances to
  be cancelled.

This method type is an iCalendar object that conforms to the following
property constraints:

     (DESCRIPTION "Journal - Cancel" COMPONENT "VJOURNAL"


Component/Property   Presence
-------------------  ---------------------------------------------
PRODID              MUST
VERSION             MUST be "2.0"
METHOD              MUST be "CANCEL"
VJOURNAL            MUST COMPONENT = CALPROPS (
          MUST PROPERTY = PRODID, VERSION{"2.0"}, METHOD{"CANCEL"})
    DTSTAMP         MUST COMPONENT = VJOURNAL (
    ORGANIZER       MUST PROPERTY = DTSTAMP, SEQUENCE{IF NE 0}, UID{UID
               associated with original REQUEST}
          MAY PROPERTY = COMMENT{provides comment from "Organizer" to
               ATTENDEE}, EXDATE, EXRULE, RECURRENCE-ID, SEQUENCE{IF EQ
               0}, STATUS{CANCELLED}
          NOT PROPERTY = ATTACH, ATTENDEE, CATEGORIES, CLASS, CREATED,
               DESCRIPTION, DTSTART, LAST-MODIFIED, RDATE, RELATED-TO,
               REQUEST-STATUS, RRULE, SUMMARY, URL)
     MAY COMPONENT = X-TOKENS (ANY)
     NOT COMPONENT = VEVENT
     NOT COMPONENT = VTODO
     NOT COMPONENT = VFREEBUSY
     NOT COMPONENT = VTIMEZONE
     NOT COMPONENT = VALARM
     )

3.4.3     REFRESH


   The "REFRESH" method in a "VJOURNAL" calendar component is used by
   "Attendees" of an existing journal entry to request an updated
   description from the journal entry "Organizer". The "REFRESH" method


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    RECURRENCE-ID   MUST specify the "UID" property corresponding only if referring to the journal entry
   needing update. A recurrence an instance of a journal entry MAY be
   requested by specifying the"RECURRENCE-ID" property corresponding to
   the associated journal entry. The "Organizer" MUST respond with the
   latest description and version of the journal entry. This method is
   intended to facilitate machine processing of the "REFRESH" response.

   This method type is an iCalendar object that conforms to the
   following property constraints:

     (DESCRIPTION "Journal - Refresh" COMPONENT "VJOURNAL" METHOD
          "REFRESH"
                         recurring calendar component.  Otherwise it
                         MUST COMPONENT = CALPROPS (
          MUST PROPERTY = PRODID, VERSION{"2.0"}, METHOD{"REFRESH"}) NOT be present.
    SEQUENCE        MUST COMPONENT = VJOURNAL (
    UID             MUST PROPERTY = ATTENDEE{address of requestor}, DTSTAMP,
               SEQUENCE{IF NE 0}, UID{UID associated with be the UID of the original
               REQUEST} REQUEST

    COMMENT         MAY
    STATUS          MAY be present, must be "CANCELLED" if present
    ATTACH          MAY PROPERTY = COMMENT{provides comment from
    ATTENDEE to
               "Organizer"}, RECURRENCE-ID, SEQUENCE{IF EQ 0}
          NOT PROPERTY = ATTACH, CATEGORIES, CLASS, CREATED,
               DESCRIPTION, DTSTART, EXDATE, EXRULE, LAST-MODIFIED,
               PRIORITY, RDATE, RELATED-TO, REQUEST-STATUS, RRULE,
               SUMMARY, URL)        MAY COMPONENT = X-TOKENS (ANY)
     NOT COMPONENT = VEVENT
     NOT COMPONENT =
    CATEGORIES      MAY


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    CLASS           MAY
    CONTACT         MAY
    CREATED         MAY
    DESCRIPTION     MAY
    DTSTART         MAY
    DTEND           MAY
    EXDATE          MAY
    EXRULE          MAY
    GEO             MAY
    LAST-MODIFIED   MAY
    %-COMPLETE      MAY
    PRIORITY        MAY
    RELATED-TO      MAY
    REQUEST-STATUS  MAY
    RESOURCES       MAY
    RDATE           MAY
    RRULE           MAY
    STATUS          MAY
    SUMMARY         MAY
    TRANSP          MAY
    URL             MAY

VTODO
     NOT COMPONENT =               MAY
VEVENT              MAY
VFREEBUSY
     NOT COMPONENT =           MAY
VTIMEZONE
     NOT COMPONENT =           MUST be present if any date/time refers to a
                        timezone
VALARM
     )


3.5              MAY
X-TOKENS            MAY


3.6 Status Replies

The "REQUEST-STATUS" property MAY may include the following values:


|==============+============================+=========================|
| Short Return | Longer Return Status       | Offending Data          |
| Status Code  | Description                |                         |
|==============+============================+=========================|
| 2.0          | Success.                   | None.                   |
|==============+============================+=========================|
| 2.1          | Success but fallback taken | Property name and value |
|              | on one or more property    | MAY be specified.       |
|              | values.                    |                         |
|==============+============================+=========================|
| 2.2          | Success, invalid property  | Property name MAY be    |
|              | ignored.                   | specified.              |
|==============+============================+=========================|
| 2.3          | Success, invalid property  | Property parameter name |
|              | parameter ignored.         | and value MAY be        |


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|              |                            | specified.              |
|==============+============================+=========================|
| 2.4          | Success, unknown non-      | Non-standard property   |


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|              | standard property ignored. | name MAY be specified.  |
|==============+============================+=========================|
| 2.5          | Success, unknown non       | Property and non-       |
|              | standard property value    | standard value MAY be   |
|              | ignored.                   | specified.              |
|==============+============================+=========================|
| 2.6          | Success, invalid calendar  | Calendar component      |
|              | component ignored.         | sentinel (e.g., "BEGIN: |
|              |                            | ALARM") MAY be          |
|              |                            | specified.              |
|==============+============================+=========================|
| 2.7          | Success, request forwarded | Original and forwarded  |
|              | to Calendar User.          | caluser addresses MAY   |
|              |                            | be specified.           |
|==============+============================+=========================|
| 2.8          | Success, repeating event   | RRULE or RDATE property |
|              | ignored. Scheduled as a    | name and value MAY be   |
|              | single event.              | specified.              |
|==============+============================+=========================|
| 2.9          | Success, truncated end date| DTEND property value    |
|              | time to date boundary.     | MAY be specified.       |
|==============+============================+=========================|
| 2.10         | Success, repeating VTODO   | RRULE or RDATE property |
|              | ignored. Scheduled as a    | name and value MAY be   |
|              | single VTODO.              | specified.              |
|==============+============================+=========================|
| 2.11         | Success, RRULE or EXRULE   | RRULE or EXRULE property|
|              | too complex. Scheduled as  | name and value MAY be   |
|              | a single event.            | specified.              |
|==============+============================+=========================|
| 2.12         | Success, unbounded RRULE   | RRULE property name and |
|              | clipped at some finite     | value MAY be specified. |
|              | number of instances        | Number of instances MAY |
|              |                            | also be specified.      |
|==============+============================+=========================|
| 3.0          | Invalid property name.     | Property name MAY be    |
|              |                            | specified.              |
|==============+============================+=========================|
| 3.1          | Invalid property value.    | Property name and value |
|              |                            | MAY be specified.       |
|==============+============================+=========================|
| 3.2          | Invalid property parameter.| Property parameter name |
|              |                            | and value MAY be        |
|              |                            | specified.              |
|==============+============================+=========================|
| 3.3          | Invalid property parameter | Property parameter name |
|              | value.                     | and value MAY be        |
|              |                            | specified.              |
|==============+============================+=========================|
| 3.4          | Invalid calendar component | Calendar component      |
|              | sequence.                  | sentinel MAY be         |
|              |                            | specified (e.g., BEGIN: |
|              |                            | VTIMEZONE).             |
|==============+============================+=========================|


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| 3.5          | Invalid date or time.      | Date/time value(s) MAY  |
|              |                            | be specified.           |
|==============+============================+=========================|
| 3.6          | Invalid rule.              | Rule value MAY be       |
|              |                            | specified.              |
|==============+============================+=========================|


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| 3.7          | Invalid Calendar User.     | Attendee property value |
|              |                            |MAY be specified.        |
|==============+============================+=========================|
| 3.8          | No authority.              | PROFILE and ATTENDEE Attendee    |
|              |                            | property values MAY be  |
|              |                            | specified.              |
|==============+============================+=========================|
| 3.9          | Unsupported version.       | VERSION property name   |
|              |                            | and value MAY be        |
|              |                            | specified.              |
|==============+============================+=========================|
| 3.10         | Request entity too large.  | None.                   |
|==============+============================+=========================|
| 3.11         | Required component or      | Component or property   |
|              | property missing.          | name MAY be specified.  |
|==============+============================+=========================|
| 4.0          | Event conflict. Date/time  | DTSTART and DTEND       |
|              | is busy.                   | property name and values|
|              |                            | MAY be specified.       |
|==============+============================+=========================|
| 5.0          | Request not MAY supported.     | Method property value   |
|              |                            | MAY be specified.       |
|==============+============================+=========================|
| 5.1          | Service unavailable.       | ATTENDEE property value |
|              |                            | MAY be specified.       |
|==============+============================+=========================|
| 5.2          | Invalid calendar service.  | ATTENDEE property value |
|              |                            | MAY be specified.       |
|==============+============================+=========================|
| 5.3          | No scheduling support for  | ATTENDEE property value |
|              | user.                      | MAY be specified.       |
|==============+============================+=========================|


3.6


3.7 Implementation Considerations


3.6.1


3.7.1     Working With Recurrence Instances

iCalendar includes a recurrence grammar to represent recurring events.
The benefit of such a grammar is the ability to represent a number of
events in a single object. However, while this simplifies creation of a
recurring event, meeting instances MAY still need to be referenced. For
instance, an "Attendee" MAY may decline the third instance of a recurring
Friday event. Similarly, the "Organizer" MAY may change the time or location
to a single instance of the recurring event.




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Since implementations MAY may elect to store recurring events as either a
single event object or a collection of discreet, related event objects,
the protocol is designed so that each recurring instance MAY may be both
referenced and versioned. Hence, implementations that choose to maintain
per-instance properties (such as "ATTENDEE" property
   "STATUS" "attstat"
parameter) MAY may do so. However, the protocol does not require
   per-instance per-
instance recognition unless the instance itself MUST must be renegotiated.


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The scenarios for recurrence instance referencing are listed below. For
purposes of simplification a change to an event refers to a "trigger
property."  That is, a property that has a substantive
   affect effect on the
meeting itself such as start time, location, due date (for "VTODO"
calendar component components) and possibly description.

      .

"Organizer" initiated actions:

. "Organizer" deletes or changes a single instance of a recurring event
. "Organizer" makes changes that affect all future instances
. "Organizer" makes changes that affect all previous instances
. "Organizer" deletes or modifies a previously changed instance

      . Attendee


"Attendee" initiated actions:

. Attendee "Attendee" changes status for a particular recurrence instance
. Attendee "Attendee" sends Event-Counter for a particular recurrence instance


An instance of a recurring event is assigned a unique identification,
"RECURRENCE-ID" property, when that instance MUST be is renegotiated.
Negotiation is may be necessary when a substantive change to the event or
to-do has be made (such as changing the start time, end time, due date
or
   location are modified. If the location). The "Organizer" wishes to can identify a specific recurrence
instance it is done using the "RECURRENCE-ID" property. The property value is equal
to the date/time of the instance. If the "Organizer" wishes to change the"DTSTART",
the "DTSTART", the original "DTSTART" value is used for"RECURRENCE-ID" for "RECURRENCE-ID"
property and the new "DTSTART" and "DTEND" values reflect the change. If the
   "Organizer" wishes to add a new instance to the recurring event then
   a "REQUEST" is issued with an "RDATE" property equal to the new
   instance date. It is recommended
Note that after the "Organizer" include change has occurred, the "RECURRENCE-ID" property[SS1]. Since has changed
to the creation of a new event
   instance requires negotiation, the sequence number is also
   incremented.

3.6.2 "DTSTART" value.


3.7.2     Attendee Property Considerations

The "ATTENDEE" "ORGANIZER" property for the "Organizer" is required on published events, to-dos, and
journal entries for two reasons. First, a
   published only the "Organizer" is allowed
to update and redistribute an event, to-do, event or journal entry to-do component. The "Organizer" "ATTENDEE" It follows that
the "ORGANIZER" property MUST be present in the event, to-do, or journal
entry component so that the "CUA" CUA has a basis for authorizing an update.
Second, it is prudent to provide a point of contact for anyone who
receives a published component in case of problems.

There are valid RFC 822 addresses that represent groups. Sending email
to such an address results in mail being sent to multiple


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Thus, it is possible that the recipient of a "REQUEST" does not appear
explicitly in the list list.

It is recommended that the general approach to finding a "Calendar User"
in an attendee list be as follows:


     1.        Search for the "Calendar User" in the attendee list where
       "TYPE=INDIVIDUAL"

     2.        Failing (1) look for attendees where "TYPE=GROUP" or
       'TYPE=UNKNOWN". The "CUA" MUST CUA then determine determines if the "CU" "Calendar User"
       is a member of one of these groups. If so, the "REPLY" method
       sent to the "Organizer" MUST contain a new "ATTENDEE" property
       in which the "TYPE" property parameter is set to INDIVIDUAL and
       the
       "GROUP" "group" property parameter is set to the name of the group.

     3. 
       Failing (2) the "CUA" MAY ignore or accept the request as the
       "Calendar User" wishes.

3.6.3     When To Refresh An Event


   An "VEVENT" or "VTODO" calendar component SHOULD be resent to all
   "Attendees" whenever the "SEQUENCE" property is incremented or any
   other substantive change is made.

3.6.4     Timezones


   If a recurring event has any instance where "DTSTART" and "DTEND"
   fall on different sides of a time zone shift, the "VTIMEZONE"
   components are required.

   The threat of duplicate time zone definitions exists. SHOULD an
   iCalendar object contain multiple conflicting time zone components,
   the one with the latest "DTSTART" property supersedes the others.

3.6.5     Alarms


   It is recommended that application software ask the user whether group.

     3.        Failing (2) the CUA MAY ignore or
   not they want alarms included when they read accept the event.

3.6.6     SUMMARY Property


   The minimum support for request as the "SUMMARY" property in a recipient MUST be
   for a 255 byte value. Implementations MAY truncate longer length
   values.






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3.6.7
       "Calendar User" wishes.

3.7.3     X-Tokens

To make iCalendar objects extensible, new property types MAY be inserted
into components. These properties are called X-Tokens as they are
prefixed with "X-". A client is not required to make sense of X-Tokens.
Clients are not required to save X-Tokens or use them in
   event replies.


4  Examples


4.1 Published Event Examples

In the calendaring and scheduling context, publication refers to the one
way transfer of event information. Consumers of published events simply
incorporate the event into a calendar. No reply is expected. Individual
"A" publishes an event. Individual "B" reads the event and incorporates
it into their calendar. Events MAY be are published in several ways including:
embedding the event as an object in a web page, e-mailing the event to a
distribution list, and posting the event to a newsgroup.

The table below illustrates the sequence of events between the publisher
and the consumers of a published event.

+-------------------------------------------------------------------+
| Action                          |  "Organizer"                    |
+---------------------------------+---------------------------------+
| Publish an event                | "A" sends or posts a PUBLISH    |
|                                 | message                         |
+---------------------------------+---------------------------------+
| "B" reads a published event     |                                 |
+---------------------------------+---------------------------------+
| Publish an updated event        | "A" sends or posts a PUBLISH    |
|                                 | message                         |


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+---------------------------------+---------------------------------+
| "B" reads the updated event     |                                 |
+---------------------------------+---------------------------------+
| Cancel a published event        | "A" sends or posts a CANCEL     |
|                                 | message                         |
+---------------------------------+---------------------------------+
| "B" reads the canceled event    |                                 |
|  publication                    |                                 |
+---------------------------------+---------------------------------+


4.1.1     A Minimal Published Event

The iCalendar object below describes a single event that begins on July
1, 1997 at 20:00 UTC. This event contains the minimum set of properties
for a "PUBLISH" for a "VEVENT" calendar component.



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BEGIN:VCALENDAR
METHOD:PUBLISH
PRODID:-//ACME/DesktopCalendar//EN
VERSION:2.0
BEGIN:VEVENT
     ATTENDEE;ROLE=OWNER:mailto:a@host.com
ORGANIZER:mailto:a@example.com
DTSTART:19970701T200000Z
DTSTAMP:19970611T190000Z
SUMMARY:ST. PAUL SAINTS -VS- DULUTH-SUPERIOR DUKES
     UID:0981234-1234234-23@host.com
UID:0981234-1234234-23@example.com
END:VEVENT
END:VCALENDAR


4.1.2     Changing A Published Event

The iCalendar object below describes an update to the event described in
4.1.1, the time has been changed, an end time has been added, and the
sequence number has been adjusted.


BEGIN:VCALENDAR
METHOD:PUBLISH
VERSION:2.0
PRODID:-//ACME/DesktopCalendar//EN
BEGIN:VEVENT
     ATTENDEE;ROLE=OWNER:mailto:A@example.com
ORGANIZER:mailto:a@example.com
DTSTAMP:19970612T190000Z
DTSTART:19970701T210000Z
DTEND:19970701T230000Z
SEQUENCE:2
     UID:0981234-1234234-23@host.com
UID:0981234-1234234-23@example.com
SUMMARY:ST. PAUL SAINTS -VS- DULUTH-SUPERIOR DUKES
END:VEVENT
END:VCALENDAR



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The "UID" property is used by the client to identify the event. The
"SEQUENCE" property indicates that this is the second change to the
event. Events with sequence numbers 0 and 1 are superseded by this
event.

The "SEQUENCE" property provides a reliable way to distinguish different
versions of the same event. Each time an event is published, its
sequence number is incremented. If a client receives an event with a
sequence number 5 and finds it has the same event with sequence number
2, the event SHOULD be updated. However, if the client received an event
with sequence number 2 and finds it already has sequence number 5 of the
same event, the event SHOULD MUST NOT be updated.






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4.1.3     Canceling A Published Event

The iCalendar object below cancels the event described in 4.1.1. This
cancels the event with "SEQUENCE" property of 0, 1, and 2.

BEGIN:VCALENDAR
METHOD:CANCEL
VERSION:2.0
PRODID:-//ACME/DesktopCalendar//EN
BEGIN:VEVENT
     ATTENDEE;ROLE=OWNER:mailto:A@example.com
ORGANIZER:mailto:a@example.com
COMMENT:DUKES forfeit the game
SEQUENCE:2
     UID:0981234-1234234-23@host.com
UID:0981234-1234234-23@example.com
DTSTAMP:19970613T190000Z
     STATUS:CANCELLED
END:VEVENT
END:VCALENDAR


4.1.4     A Rich Published Event

This example describes the same event as in 4.1.1, but in much greater
detail.

BEGIN:VCALENDAR
PRODID:-//ACME/DesktopCalendar//EN
METHOD:PUBLISH
SCALE:GREGORIAN
SOURCE:http://www.midwaystadium.com/stadium-cal/1997-events.or4
     NAME:1997 GAME SCHEDULE
VERSION:2.0
BEGIN:VTIMEZONE
     DAYLIGHT:TRUE
     DTSTART:19970406T070000-0600
     RRULE:FREQ=YEARLY;BYDAY=1SU;BYMONTH=4
     TZNAME:CDT
     TZOFFSET:-0500
     END:VTIMEZONE

     BEGIN:VTIMEZONE
     DAYLIGHT:FALSE
     DTSTART:19971026T0200-0500
TZID:America-Chicago
TZURL:http://zones.stds_r_us.net/tz/America-Chicago
LAST-MODIFIED:19870101T000000Z
BEGIN:STANDARD
DTSTART:19671029T020000
RRULE:FREQ=YEARLY;BYDAY=-1SU;BYMONTH=10
TZOFFSETFROM:-0500
TZOFFSETTO:-0600
TZNAME:CST
     TZOFFSET:-0600
     END:VTIMEZONE

     BEGIN:VEVENT
     ATTENDEE;ROLE=OWNER:mailto:A@example.com


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END:STANDARD
BEGIN:DAYLIGHT
DTSTART:19870405T020000
RRULE:FREQ=YEARLY;BYDAY=1SU;BYMONTH=4
TZOFFSETFROM:-0600
TZOFFSETTO:-0500
TZNAME:CDT
END:DAYLIGHT
END:VTIMEZONE
BEGIN:VEVENT
ORGANIZER:mailto:a@example.com
ATTACH:http://www.midwaystadium.com
CATEGORIES:SPORTS EVENT;ENTERTAINMENT EVENT,ENTERTAINMENT
CLASS:PRIVATE
CREATED:19970415T194319Z
DESCRIPTION:MIDWAY STADIUM\n
 Big time game. MUST see.\n
 Expected duration:2 hours\n
     DTEND:19970701T180000
     DTSTART:19970702T160000
DTEND;TZID=America-Chicago:19970701T180000
DTSTART;TZID=America-Chicago:19970702T160000
DTSTAMP:19970614T190000Z
STATUS:CONFIRMED
LAST-MODIFIED:19970416T162421Z
LOCATION;VALUE=URL:http://www.midwaystadium.com/
PRIORITY:2
RESOURCES:SCOREBOARD
SEQUENCE:3
SUMMARY:ST. PAUL SAINTS -VS- DULUTH-SUPERIOR DUKES
     UID:0981234-1234234-23@host.com
     RELATED-TO:0981234-1234234-14@host.com
UID:0981234-1234234-23@example.com
RELATED-TO:0981234-1234234-14@example.com

BEGIN:VALARM
     DTSTART:19970701T190000Z
     REPEAT:2
     DURATION:PT2H
     CATEGORIES:DISPLAY,AUDIO
TRIGGER:PT2H
ALARM-TYPE:DISPLAY
DESCRIPTION:It's almost game time
END:VALARM

BEGIN:VALARM
     DTSTART:19970701T153000
     CATEGORIES:DISPLAY,AUDIO
TRIGGER:PT30M
ALARM-TYPE:AUDIO
DESCRIPTION:You SHOULD leave now. Game starts in 30 min! minutes!
END:VALARM
END:VEVENT
END:VCALENDAR

The "CLASS" property is specified, though it is not really needed
   here. Since this is a published event, a program that displays it
   need not apply any content filtering based on the "CLASS" attribute.
   If this event is copied into a user's calendar, the "CLASS" would be
   included as part of the copy.  The handling of the "CLASS" tag at
   that point is implementation specific.

   The "RELATED-TO" field contains the "UID" property of a related calendar
event. The handling of this property is application
   dependent.

   The "SEQUENCE" property 3 indicates that this event supersedes
versions 0, 1, and 2.





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4.1.5     Anniversaries or Events attached to entire days

This example demonstrates the use of the "value" parameter to tie a
VEVENT to day rather than a specific time.


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BEGIN:VCALENDAR
PRODID:-//ACME/DesktopCalendar//EN
METHOD:PUBLISH
VERSION:2.0
BEGIN:VEVENT
DTSTAMP:19970614T190000Z
     UID:0981234-1234234-23@host.com
UID:0981234-1234234-23@example.com
DTSTART;VALUE=DATE:19970714
RRULE:FREQ=YEARLY;INTERVAL=1
SUMMARY: Bastille Day
END:VEVENT
END:VCALENDAR


4.2 Group Event Examples

Group events are distinguished from published events in that they have
"Attendees" and that there is interaction between the "Attendees" and
the "Organizer" with respect to the event. Individual "A" requests a
meeting between individuals "A", "B", "C" and "D". Individual "B"
confirms attendance to the meeting. Individual "C" declines attendance.
Individual "D" tentatively confirms their attendance.
   This is sometimes referred to as "penciling-in" the event on a
   calendar. The following table
illustrates the sequence of messages
   that would be exchanged the message flow between these individuals. The table below
   illustrates A, the message flow. CU
scheduling the meeting, is referenced as the "Organizer".

+--------------------------------------------------------------------+
| Action             |  "Organizer"        | Attendee                |
+--------------------------------------------------------------------+
| Initiate a meeting | "A" sends a REQUEST |                         |
| request            | message to "B", "C",|                         |
|                    | and "D"             |                         |
+--------------------------------------------------------------------+
| Accept the meeting |                     | "B" sends a REPLY       |
| request            |                     | message to "A" with its |
|                    |                     | ATTENDEE STATUS para-   | "attstat" para-|
|                    |                     | set to "ACCEPTED" "accepted"       |
+--------------------------------------------------------------------+
| Decline the meeting|                     | "C" sends a REPLY       |
| request            |                     | message to "A" with its |
|                    |                     | ATTENDEE STATUS para-   | "attstat" para-|
|                    |                     | set to "DECLINED" "declined"       |
+--------------------------------------------------------------------+
| Tentatively accept |                     | "D" sends a REPLY       |
| the meeting request|                     | message to "A" with its |
|                    |                     | ATTENDEE STATUS para-   |


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| ATTENDEE "attstat" para-|
|                    |                     | set to "TENTATIVE" "tentative"      |
+--------------------------------------------------------------------+
| Confirm meeting    | "A" sends a REQUEST |                         |
| status with        | message to "B" and  |                         |
| attendees          | "C" with updated    |                         |
|                    | information.        |                         |
+--------------------------------------------------------------------+




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4.2.1     A Group Event Request

A sample meeting request that is sent from "A" sends to "B", "C", and "D". _E_ is
also sent a copy of the request but is not expected to attend and need
not reply. "E" illustrates how CUAs might implement a "CC" type feature.
Note the use of the "role" parameter. The default value for the "role"
parameter is "req-participant" and it need not be enumerated. In this
case we are using the value "non-participant" to indicate "E" is a non-
attending CU. The parameter is not needed on other "Attendees" since
"participant" is the default value.


BEGIN:VCALENDAR
PRODID:-//ACME/DesktopCalendar//EN
METHOD:REQUEST
VERSION:2.0
BEGIN:VEVENT
     ATTENDEE;ROLE=OWNER:Mailto:A@example.com
     ATTENDEE;ROLE=ATTENDEE;STATUS=ACCEPTED:Mailto:A@example.com
     ATTENDEE;RSVP=TRUE;EXPECT=REQUEST;TYPE=INDIVIDUAL:Mailto:B@example.
com
     ATTENDEE;RSVP=TRUE;EXPECT=REQUEST;TYPE=INDIVIDUAL:Mailto:C@example.
com
     ATTENDEE;RSVP=TRUE;EXPECT=REQUEST;TYPE=INDIVIDUAL:Mailto:D@example.
com
     ATTENDEE;RSVP=FALSE;EXPECT=REQUIRE;TYPE=ROOM:CR_Big@example.com
ORGANIZER:Mailto:A@example.com
ATTENDEE;ROLE=CHAIR;ATTSTAT=ACCEPTED;CN=BIG A:Mailto:A@example.com
ATTENDEE;RSVP=TRUE;TYPE=INDIVIDUAL;CN=B:Mailto:B@example.com
ATTENDEE;RSVP=TRUE;TYPE=INDIVIDUAL;CN=C:Mailto:C@example.com
ATTENDEE;RSVP=TRUE;TYPE=INDIVIDUAL;CN=Hal:Mailto:D@example.com
ATTENDEE;RSVP=FALSE;TYPE=ROOM:conf_Big@example.com
ATTENDEE;ROLE=NON-PARTICIPANT;RSVP=FALSE:Mailto:E@example.com
DTSTAMP:19970611T190000Z
     DTSTART:19970701T100000-0700
     DTEND:19970701T103000-0700
DTSTART:19970701T200000Z
DTEND:19970701T203000Z
SUMMARY:Phone Conference
     UID:www.acme.com-873970198738777@host.com
UID:www.acme.com-873970198738777@example.com
SEQUENCE:0
STATUS:CONFIRMED
END:VEVENT
END:VCALENDAR


4.2.2     Reply To A Group Event Request

Attendee "B" accepts the meeting.


BEGIN:VCALENDAR
PRODID:-//ACME/DesktopCalendar//EN
METHOD:REPLY
VERSION:2.0
BEGIN:VEVENT
     ATTENDEE;STATUS=ACCEPTED:Mailto:B@example.com
     UID:www.acme.com-873970198738777@host.com
ATTENDEE;ATTSTAT=ACCEPTED:Mailto:B@example.com
ORGANIZER:MAILTO:A@example.com
UID:www.acme.com-873970198738777@example.com
SEQUENCE:0
REQUEST-STATUS:2.0;Success
DTSTAMP:19970612T190000Z
END:VEVENT
END:VCALENDAR



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     END:VEVENT
     END:VCALENDAR                       March 13, 1998


"B" could have declined the meeting or indicated tentative acceptance by
setting the ATTENDEE;"STATUS" ATTENDEE "attstat" parameter to DECLINED "declined" or TENTATIVE, "tentative",
respectively. Also, "REQUEST-STATUS" is not required on a successful
transactions.


4.2.3     Update An Event

The event is moved to a different time. The combination of the "UID"
   property(which remains the same)
property (unchanged) and the SEQUENCE "SEQUENCE" (bumped to 1) properties
indicate the update.


BEGIN:VCALENDAR
PRODID:-//ACME/DesktopCalendar//EN
METHOD:REQUEST
VERSION:2.0
BEGIN:VEVENT
     ATTENDEE;ROLE=OWNER:Mailto:A@example.com
     ATTENDEE;ROLE=ATTENDEE;STATUS=ACCEPTED:Mailto:A@example.com
     ATTENDEE;RSVP=TRUE;EXPECT=REQUEST;TYPE=INDIVIDUAL:Mailto:B@example.
com
     ATTENDEE;RSVP=TRUE;EXPECT=REQUEST;TYPE=INDIVIDUAL:Mailto:C@example.
com
     ATTENDEE;RSVP=TRUE;EXPECT=REQUEST;TYPE=INDIVIDUAL:Mailto:D@example.
com
     ATTENDEE;RSVP=FALSE;EXPECT=REQUIRE;TYPE=ROOM:CR_Big@example.com
     DTSTART:19970701T110000-0700
     DTEND:19970701T113000-0700
ORGANIZER:Mailto:A@example.com
ATTENDEE;ROLE=CHAIR;ATTSTAT=ACCEPTED:Mailto:A@example.com
ATTENDEE;RSVP=TRUE;TYPE=INDIVIDUAL:Mailto:B@example.com
ATTENDEE;RSVP=TRUE;TYPE=INDIVIDUAL:Mailto:C@example.com
ATTENDEE;RSVP=TRUE;TYPE=INDIVIDUAL:Mailto:D@example.com
ATTENDEE;RSVP=FALSE;TYPE=ROOM:Mailto:Conf@example.com
ATTENDEE;ROLE=NON-PARTICIPANT;RSVP=FALSE:Mailto:E@example.com
DTSTART:19970701T180000Z
DTEND:19970701T1200000Z
SUMMARY:Phone Conference
     UID:www.acme.com-873970198738777@host.com
UID:www.acme.com-873970198738777@example.com
SEQUENCE:1
DTSTAMP:19970613T190000Z
STATUS:CONFIRMED
END:VEVENT
END:VCALENDAR


4.2.4     Countering an Event Proposal


   Attendee A

"A" sends a "REQUEST" to B "B" and C. B "C". "B" makes a counter proposal counter-proposal to
   A
"A" to change the time and location.

   Attendee A

"A" sends the following "REQUEST":


BEGIN:VCALENDAR
PRODID:-//ACME/DesktopCalendar//EN
METHOD:REQUEST
VERSION:2.0
BEGIN:VEVENT
     ATTENDEE;ROLE=OWNER:Mailto:A@example.com
ORGANIZER:Mailto:A@example.com
ATTENDEE;ROLE=CHAIR;ATTSTAT=ACCEPTED:Mailto:A@example.com
ATTENDEE;RSVP=TRUE;TYPE=INDIVIDUAL:Mailto:B@example.com
ATTENDEE;RSVP=TRUE;TYPE=INDIVIDUAL:Mailto:C@example.com



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     ATTENDEE;ROLE=ATTENDEE;STATUS=ACCEPTED:Mailto:A@example.com
     ATTENDEE;RSVP=TRUE;EXPECT=REQUEST;TYPE=INDIVIDUAL:Mailto:B@example.
     com
     ATTENDEE;RSVP=TRUE;EXPECT=REQUEST;TYPE=INDIVIDUAL:Mailto:C@example.
com                       March 13, 1998


DTSTART:19970701T190000Z
DTEND:19970701T200000Z
SUMMARY:Discuss the Merits of the election results
LOCATION:The Big Conference Room
     UID:www.acme.com-873970198738777@host.com
UID:www.acme.com-873970198738777@example.com
SEQUENCE:0
DTSTAMP:19970611T190000Z
STATUS:CONFIRMED
END:VEVENT
END:VCALENDAR


   Attendee B

"B" sends "COUNTER" to A, "A", requesting changes to time and
   place: place. "B"
uses the "COMMENT" property to communicate a rationale for the change:


BEGIN:VCALENDAR
PRODID:-//ACME/DesktopCalendar//EN
METHOD:COUNTER
VERSION:2.0
BEGIN:VEVENT
     ATTENDEE;ROLE=OWNER:Mailto:A@example.com
     ATTENDEE;ROLE=ATTENDEE;STATUS=ACCEPTED:Mailto:A@example.com
     ATTENDEE;RSVP=TRUE;EXPECT=REQUEST;TYPE=INDIVIDUAL:Mailto:B@example.
     com
     ATTENDEE;RSVP=TRUE;EXPECT=REQUEST;TYPE=INDIVIDUAL:Mailto:C@example.
com
ORGANIZER:Mailto:A@example.com
ATTENDEE;ROLE=CHAIR;ATTSTAT=ACCEPTED:Mailto:A@example.com
ATTENDEE;RSVP=TRUE;TYPE=INDIVIDUAL:Mailto:B@example.com
ATTENDEE;RSVP=TRUE;TYPE=INDIVIDUAL:Mailto:C@example.com
DTSTART:19970701T160000Z
DTEND:19970701T190000Z
DTSTAMP:19970612T190000Z
SUMMARY:Discuss the Merits of the election results
LOCATION:The Small Conference Room
COMMENT:This time works much better and I think the big conference
  room is too big
     UID:www.acme.com-873970198738777@host.com
UID:www.acme.com-873970198738777@example.com
SEQUENCE:0
DTSTAMP:19970611T190000Z
END:VEVENT
END:VCALENDAR


   Attendee A

"A" accepts the changes from B "B". To accept a counter-proposal, the
"Organizer" sends a new Event REQUEST with an incremented sequence
number.


BEGIN:VCALENDAR
PRODID:-//ACME/DesktopCalendar//EN
METHOD:REQUEST
VERSION:2.0
BEGIN:VEVENT
     ATTENDEE;ROLE=OWNER:Mailto:A@example.com
     ATTENDEE;ROLE=ATTENDEE;STATUS=ACCEPTED:Mailto:A@example.com
ORGANIZER:Mailto:A@example.com
ATTENDEE;ROLE=CHAIR;ATTSTAT=ACCEPTED:Mailto:A@example.com
ATTENDEE;RSVP=TRUE;TYPE=INDIVIDUAL:Mailto:B@example.com
ATTENDEE;RSVP=TRUE;TYPE=INDIVIDUAL:Mailto:C@example.com
DTSTAMP:19970613T190000Z
DTSTART:19970701T160000Z
DTEND:19970701T190000Z


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     ATTENDEE;RSVP=TRUE;EXPECT=REQUEST;TYPE=INDIVIDUAL:Mailto:B@example.
com
     ATTENDEE;RSVP=TRUE;EXPECT=REQUEST;TYPE=INDIVIDUAL:Mailto:C@example.
com
     DTSTAMP:19970613T190000Z
     DTSTART:19970701T160000Z
     DTEND:19970701T190000Z                       March 13, 1998


SUMMARY:Discuss the Merits of the election results - changed to
       suite
  meet B's schedule
LOCATION:The Small Conference Room
     UID:www.acme.com-873970198738777@host.com
UID:www.acme.com-873970198738777@example.com
SEQUENCE:1
STATUS:CONFIRMED
END:VEVENT
END:VCALENDAR


   A

Instead, "A" rejects B's "B's" counter proposal

BEGIN:VCALENDAR
PRODID:-//ACME/DesktopCalendar//EN
METHOD:DECLINECOUNTER
VERSION:2.0
BEGIN:VEVENT
     ATTENDEE;ROLE=OWNER:Mailto:A@example.com
     ATTENDEE;ROLE=ATTENDEE;STATUS=ACCEPTED:Mailto:A@example.com
     ATTENDEE;RSVP=TRUE;EXPECT=REQUEST;TYPE=INDIVIDUAL:Mailto:B@example.
com
ORGANIZER:Mailto:A@example.com
ATTENDEE;RSVP=TRUE;TYPE=INDIVIDUAL:Mailto:B@example.com
COMMENT:Sorry, I cannot change this meeting time
     UID:www.acme.com-873970198738777@host.com
UID:www.acme.com-873970198738777@example.com
SEQUENCE:1
DTSTAMP:19970614T190000Z
END:VEVENT


4.2.5     Delegate An     Delegating an Event

When delegating an event request to another "Calendar User", the
   "delegator" MUST
"Delegator" must both update the "Organizer" with a "REPLY" and send a
request to the "delegatee". "Delegate". There is currently no protocol limitation to
delegation depth. It is possible for the original delegate to delegate
the meeting to someone else, and so on. When a request is delegated from
one "CUA" CUA to another there are a number of responsibilities required of
the "delegator". "Delegator". They MUST:

. Send an REPLY to the "Organizer" with their attendee/status "ATTENDEE" property
  "attstat" parameter set to "Delegated" "delegated"
. Include the delegate as an additional attendee "Attendee" with the
        "Delegated-From" "delegated-
  from" property parameter set to the value of the delegator
. Include the original UID of the REQUEST



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. The delegator "Delegator" MUST also send a copy of the original REQUEST "REQUEST"
  method to the delegate. "Delegate". The delegator modifies the request to include: as
  follows:
. The ATTENDEE/STATUS "ATTENDEE" property "attstat" parameter for the delegator (sender
  in this case) is set to "DELEGATED" "delegated"
. ATTENDEE/DELEGATED-TO "ATTENDEE" "delegated-to" parameter is set to the address of the
        delegatee
  "Delegate"
. An ATTENDEE "ATTENDEE" property is added for delegatee

   As a rule, it the "Delegate"


It is not required that the "delegatee" "Delegate" include the
   "delegator" "Delegator" in their
"REPLY" method. However, it is strongly advised since this will inform
the "delegator" "Delegator" whether their proxy the "Delegate" plans to attend the meeting. If



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the "delegatee" "Delegate" declines the meeting, the
   "delegator" MAY "Delegator" may elect to try and
delegate the "REQUEST" to another
   "CUA". CUA. The process is the same.


+---------------------------------------------------------------------+
| Action             |  "Organizer"        | Attendee                 |
+---------------------------------------------------------------------+
| Initiate a meeting | "A" sends a REQUEST |                          |
| request            | message to "B" and  |                          |
|                    | "C"                 |                          |
+---------------------------------------------------------------------+
| Delegate:          |                     | "C" sends a REPLY to "A" |
| "C" delegates to   |                     | with the ATTENDEE.STATUS ATTENDEE.       |
| "E"                |                     | parameter "attstat"parameter set to         | to|
|                    |                     | "DELEGATED" "delegated" and with a   |
|                    |                     | new ATTENDEE "ATTENDEE" property  |
|                    |                     | for "E". "E's" ATTENDEE  |
|                    |                     | DELEGATED-FROM property "delegated-from" param   |
|                    |                     | is set to "C". "C's"     |
|                    |                     | ATTENDEE.DELEGATED-TO ATTENDEE "delegated-to"  |
|                    |                     | property param is set to "E".     |
|                    |                     | "C" sends REQUEST message|
|                    |                     | to "E" with the original |
|                    |                     | meeting request          |
|                    |                     | information. The         |
|                    |                     | ATTENDEE/STATUS  "attstat" property      |
|                    |                     | parameter for "C" is set |
|                    |                     | to "DELEGATED" "delegated" and the   |
|                    |                     | ATTENDEE/DELEGATED-TO  "delegated-to"          |
|                    |                     | parameter is set to      |
|                    |                     | the address of "E". An   |
|                    |                     | ATTENDEE "ATTENDEE" property is   |
|                    |                     | added for "E" and the    |
|                    |                     | ATTENDEE/DELEGATED-FROM "delegated-from"         |
|                    |                     | parameter is set to      |
|                    |                     | the address of "C".      |
+---------------------------------------------------------------------+
| Confirm meeting    |                     | "E" sends REPLY message  |
| attendance         |                     | to "A" and optionally "C"|
|                    |                     | with its ATTENDEE/STATUS "attstat"       |
|                    |                     | property parameter set   |


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|                    |                     | to "ACCEPTED" "accepted"            |
+---------------------------------------------------------------------+
| Optional:          | "A" sends REQUEST   |                          |
| Redistribute       | message to "B", "C" |                          |
| meeting to         | and "E". SEQUENCE   |                          |
| attendees          | number is now 1.    |                          |
+---------------------------------------------------------------------+


   Attendee

"C" responds to meeting "Organizer" "A" the "Organizer".

BEGIN:VCALENDAR
PRODID:-//ACME/DesktopCalendar//EN
METHOD:REPLY


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VERSION:2.0
BEGIN:VEVENT
     ATTENDEE;ROLE=ATTENDEE;STATUS=DELEGATED;DELEGATED-
      TO="Mailto:E@example.com":Mailto:C@example.com
     UID:www.acme.com-873970198738777@host.com
ORGANIZER:MAILTO:A@Example.com
ATTENDEE;ATTSTAT=DELEGATED;DELEGATED-
TO=Mailto:E@example.com:Mailto:C@example.com
UID:www.acme.com-873970198738777@example.com
SEQUENCE:0
REQUEST-STATUS:2.0;Success
DTSTAMP:19970611T190000Z
END:VEVENT
END:VCALENDAR

Attendee "C" delegates presence at the meeting to "E".

BEGIN:VCALENDAR
PRODID:-//ACME/DesktopCalendar//EN
METHOD:REQUEST
VERSION:2.0
BEGIN:VEVENT
     ATTENDEE;ROLE=ORGANIZER:Mailto:A@example.com
     ATTENDEE;ROLE=ATTENDEE;STATUS=ACCEPTED:Mailto:A@example.com
     ATTENDEE;ROLE=DELEGATE;RSVP=TRUE;EXPECT=REQUEST;
      DELEGATED-FROM=_Mailto:C@example.com_:Mailto:E@example.com
     ATTENDEE;ROLE=ATTENDEE;STATUS=DELEGATED;
      DELEGATED-TO="Mailto:E@example.com":Mailto:C@example.com
     DTSTART:19970701T110000-0700
     DTEND:19970701T113000-0700
ORGANIZER:Mailto:A@example.com
ATTENDEE;ATTSTAT=DELEGATED;DELEGATED-
TO=Mailto:E@example.com:Mailto:C@example.com
ATTENDEE;ROLE=DELEGATE;RSVP=TRUE;
 DELEGATED-FROM=Mailto:C@example.com:Mailto:E@example.com
DTSTART:19970701T180000Z
DTEND:19970701T120000Z
SUMMARY:Phone Conference
     UID:www.acme.com-873970198738777@host.com
UID:www.acme.com-873970198738777@example.com
SEQUENCE:0
STATUS:CONFIRMED
DTSTAMP:19970611T190000Z
END:VEVENT
END:VCALENDAR








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4.2.6     Delegate Accepts the Meeting

To accept a delegated meeting, the delegate delegate, "E", sends the following
message to "A" and "C"


BEGIN:VCALENDAR
PRODID:-//ACME/DesktopCalendar//EN
METHOD:REPLY
VERSION:2.0
BEGIN:VEVENT
     ATTENDEE;ROLE=ATTENDEE;STATUS=CONFIRMED;
      DELEGATED-FROM="Mailto:C@example.com":Mailto:E@example.com
     UID:www.acme.com-873970198738777@host.com
ORGANIZER:MAILTO:A@Example.com
ATTENDEE;ATTSTAT=CONFIRMED;DELEGATED-
FROM=Mailto:C@example.com:Mailto:E@example.com
ATTENDEE;ATTSTAT=DELEGATED;DELEGATED-
TO=Mailto:E@example.com:Mailto:C@example.com
UID:www.acme.com-873970198738777@example.com
SEQUENCE:1
REQUEST-STATUS:2.0;Success


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DTSTAMP:19970614T190000Z
END:VEVENT
END:VCALENDAR


4.2.7     Delegate Declines the Meeting

In this example the delegate "Delegate" declines the meeting request and sets the
"ATTENDEE" property "STATUS" "attstat" parameter to DECLINED. The "Organizer"
SHOULD resend the "REQUEST" to "C" with the status "attstat" parameter of the
   delegate
"Delegate" set to DECLINED. "declined". This lets the "delegator" "Delegator" know that the
   "delegate"
"Delegate" has declined and provides an opportunity to the
   "delegator" "Delegator"
to either accept or delegate the request or delegate it to another
   "Calendar User". CU.

Response from "E" to "A" and "C".


BEGIN:VCALENDAR
PRODID:-//ACME/DesktopCalendar//EN
METHOD:REPLY
VERSION:2.0
BEGIN:VEVENT
     ATTENDEE;ROLE=ATTENDEE;STATUS=DECLINED;
      DELEGATED-FROM="Mailto:C@example.com":Mailto:E@example.com
     UID:www.acme.com-873970198738777@host.com
ORGANIZER:MAILTO:A@Example.com
ATTENDEE;ATTSTAT=DECLINED;DELEGATED-
FROM=Mailto:C@example.com:Mailto:E@example.com
UID:www.acme.com-873970198738777@example.com
ATTENDEE;ATTSTAT=DELEGATED;DELEGATED-
TO=Mailto:E@example.com:Mailto:C@example.com
SEQUENCE:1
REQUEST-STATUS:2.0;Success
DTSTAMP:19970614T190000Z
END:VEVENT
END:VCALENDAR

"A" resends the "REQUEST" method to "C". "A" MAY may also wish to express
the fact that the item was delegated in the "COMMENT" property.


BEGIN:VCALENDAR
PRODID:-//ACME/DesktopCalendar//EN


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METHOD:REPLY
VERSION:2.0
BEGIN:VEVENT
     ATTENDEE;ROLE=ATTENDEE;STATUS=DECLINED;
      DELEGATED-FROM="Mailto:C@example.com":Mailto:E@example.com
     ATTENDEE;RSVP=TRUE;EXPECT=REQUEST;TYPE=INDIVIDUAL:Mailto:C@example.
com
     UID:www.acme.com-873970198738777@host.com
ORGANIZER:MAILTO:A@Example.com
ATTENDEE;ATTSTAT=DECLINED;DELEGATED-
FROM=Mailto:C@example.com:Mailto:E@example.com
ATTENDEE;RSVP=TRUE;TYPE=INDIVIDUAL:Mailto:C@example.com
UID:www.acme.com-873970198738777@example.com
SEQUENCE:2
REQUEST-STATUS:2.0;Success
DTSTAMP:19970614T200000Z
COMMENT:DELEGATE (ATTENDEE Mailto:E@example.com) DECLINED YOUR
 INVITATION
END:VEVENT


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END:VCALENDAR


4.2.8     Forwarding an Event Request

The protocol does not prevent an "Attendee" from "forwarding" an
"VEVENT" calendar component to other "Calendar Users". Forwarding
differs from delegation in that the forwarded "Calendar User" (often
referred to as a "Party Crasher") does not replace the forwarding
"Calendar User". Implementations are not required to add the "Party
Crasher" to the "Attendee" list and hence there is no guarantee that a
"Party Crasher" will receive additional updates to the Event. The
forwarding "Calendar User" SHOULD NOT add the "Party Crasher" to the
attendee list. The "Organizer" MAY add the forwarded "Calendar User" to
the attendee list.


4.2.9     Cancel A Group Event

Individual "A" requests a meeting between individuals "A", "B" "B", "C", and
   "C".
"D". Individual "B" declines attendance to the meeting. Individual "A"
decides to cancel the meeting. The following table illustrates the
sequence of messages that would be exchanged between these individuals.

Messages related to a previously canceled event ("SEQUENCE" property
value is less than the "SEQUENCE" property value of the "CANCEL"
message) or "VTODO" calendar component MUST be ignored.


+--------------------------------------------------------------------+
| Action             |  "Organizer"        | Attendee "Attendee"              |
+--------------------------------------------------------------------+
| Initiate a meeting | "A" sends a REQUEST |                         |
| request            | message to "B", "C",|                         |
|                    | and "D"             |                         |
+--------------------------------------------------------------------+
| Decline the meeting|                     | "B" sends a "REPLY"     |
| request            |                     | message to "A" with its |
|                    |                     | "attstat" para-         |
|                    |                     | set to "declined".      |
+--------------------------------------------------------------------+
| Cancel the meeting | "A" sends a CANCEL  |                         |
|                    | message to "B", "C" |                         |
|                    | and "D"             |                         |
+--------------------------------------------------------------------+

The example shows how "A" cancels the event.

BEGIN:VCALENDAR
PRODID:-//ACME/DesktopCalendar//EN
METHOD:CANCEL
VERSION:2.0
BEGIN:VEVENT
ORGANIZER:Mailto:A@example.com


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ATTENDEE;TYPE=INDIVIDUAL;Mailto:A@example.com
ATTENDEE;TYPE=INDIVIDUAL:Mailto:B@example.com
ATTENDEE;TYPE=INDIVIDUAL:Mailto:C@example.com
ATTENDEE;TYPE=INDIVIDUAL:Mailto:D@example.com
COMMENT:Mr. B cannot attend. It's raining. Lets cancel.
UID:www.acme.com-873970198738777@example.com
SEQUENCE:0
STATUS:CANCELLED
DTSTAMP:19970613T190000Z
END:VEVENT
END:VCALENDAR


4.2.10    Removing Attendees

"A" wants to remove "B" from a meeting. This is done by sending a
"CANCEL" to "B" and removing "B" from the attendee list in the master
copy of the event.

+--------------------------------------------------------------------+
| Action             |  "Organizer"        | "Attendee"              |
+--------------------------------------------------------------------+
| Initiate a meeting Remove an "B"      | "A" sends a REQUEST CANCEL  |                         |
| request as an "Attendee"   | message to "B" and  |                         |
|                    | and "C"      |                         |
+--------------------------------------------------------------------+
| Decline Update the meeting| master  | "B" "A" sends a REPLY the       |                         | request
| copy of the event  | message updated event to "A" with its    |                         |
|                    | ATTENDEE STATUS para- the remaining       |                         |
|                    | set to "DECLINED". "Attendees"         |                         |
+--------------------------------------------------------------------+

The original meeting includes "A", "B", "C", and "D". The example below
shows the "CANCEL" that "A" sends to "B". Note that in the example below
the "STATUS" property is omitted. This is used when the meeting itself
is cancelled and not when the intent is to remove an "Attendee" from the
Event.

BEGIN:VCALENDAR
PRODID:-//ACME/DesktopCalendar//EN
METHOD:CANCEL
VERSION:2.0
BEGIN:VEVENT
ORGANIZER:Mailto:A@example.com
COMMENT:You're off the hook for this meeting
UID:www.acme.com-873970198738777@example.com
DTSTAMP:19970613T193000Z
END:VEVENT
END:VCALENDAR

The updated master copy of the event is shown below. The "Organizer" MAY
resend the updated event to the remaining "Attendees". Note that "B" has
been removed.

BEGIN:VCALENDAR


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+--------------------------------------------------------------------+
| Cancel                       March 13, 1998


PRODID:-//ACME/DesktopCalendar//EN
METHOD:REQUEST
VERSION:2.0
BEGIN:VEVENT
ORGANIZER:Mailto:A@example.com
ATTENDEE;ROLE=CHAIR;ATTSTAT=ACCEPTED:Mailto:A@example.com
ATTENDEE;TYPE=INDIVIDUAL:Mailto:C@example.com
ATTENDEE;TYPE=INDIVIDUAL:Mailto:D@example.com
ATTENDEE;TYPE=ROOM:CR_Big@example.com
ATTENDEE;ROLE=NON-PARTICIPANT;
 RSVP=FALSE:Mailto:E@example.com
DTSTAMP:19970611T190000Z
DTSTART:19970701T200000Z
DTEND:19970701T203000Z
SUMMARY:Phone Conference
UID:www.acme.com-873970198738777@example.com
SEQUENCE:0
STATUS:CONFIRMED
END:VEVENT
END:VCALENDAR

4.2.11    Replacing the Organizer

The scenario for this example begins with "A" as the "Organizer" for a
recurring meeting | with "B", "C", and "D". "A" sends receives a CANCEL  |                         |
|                    | message new job offer
in another country and leaves without changing the "Organizer" to this
meeting.  "A" left no forwarding address or way to be reached.  Using
out-of-band communication, the other "Attendees" eventually learn what
has happened and reach an agreement that "B" should become the new
"Organizer" for the meeting. To do this, "B" sends out a new version of
the event and  |                         |
|                    | "C"                 |                         |
+--------------------------------------------------------------------+


   The example shows how the other "Attendees" agree to accept "B" as the new
"Organizer". "B" also removes "A" cancels from the event. event

This is the message "B" sends to "C" and "D"

BEGIN:VCALENDAR
PRODID:-//ACME/DesktopCalendar//EN
     METHOD:CANCEL
METHOD:REQUEST
VERSION:2.0
BEGIN:VEVENT
     COMMENT:Mr. B cannot attend. I'll reschedule the meeting later.
     UID:www.acme.com-873970198738777@host.com
     SEQUENCE:0
     DTSTAMP:19970613T190000Z
     STATUS:CANCELLED
ORGANIZER:Mailto:B@example.com
ATTENDEE;ROLE=CHAIR;STATUS=ACCEPTED:Mailto:B@example.com
ATTENDEE;TYPE=INDIVIDUAL:Mailto:C@example.com
ATTENDEE;TYPE=INDIVIDUAL:Mailto:D@example.com
DTSTAMP:19970611T190000Z
DTSTART:19970701T200000Z
DTEND:19970701T203000Z
RRULE:FREQ=WEEKLY
SUMMARY:Phone Conference
UID:123456@example.com
SEQUENCE:1
STATUS:CONFIRMED
END:VEVENT
END:VCALENDAR


   The "Organizer"


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4.3 Busy Time Examples

Busy time objects can be used in several ways. First, a CU may Request
busy time from another CU for a specific range of time. That request can
be answered with a meeting MAY "uninvite" or remove "Attendees" by
   sending busy time Reply. Additionally, a "CANCEL" method CU may simply
publish busy their busy time for a given interval and point other CUs to only those "Attendees".

4.3
the published location. The following examples outline both scenarios.

Individual "A" publishes Busy Time Examples time for one week.

BEGIN:VCALENDAR
PRODID:-//ACME/DesktopCalendar//ENVERSION:2.0
METHOD:PUBLISH
BEGIN:VFREEBUSY
DTSTAMP:19980101T124100Z
ATTENDEE:MAILTO:A@Example.com
DTSTART:19980101T124200Z
DTEND:19980107T124200Z
FREEBUSY:19980101T180000Z/19980101T190000Z
FREEBUSY:19980103T020000Z/19980103T050000Z
FREEBUSY:19980107T020000Z/19980107T050000Z
FREEBUSY:19980113T000000Z/19980113T010000Z
FREEBUSY:19980115T190000Z/19980115T200000Z
FREEBUSY:19980115T220000Z/19980115T230000Z
FREEBUSY:19980116T013000Z/19980116T043000Z
END:VFREEBUSY
END:VCALENDAR


Individual "A" requests busy time from individuals "B", "C" and "D". "C". Individual
"B" and "C" replies with busy time data to individual "A".
   Individual "D" does not support busy time requests and does not reply
   with any data. The following
table illustrates the sequence of messages that would be exchanged
between these individuals.

+--------------------------------------------------------------------+
| Action             |  "Organizer"        | Attendee                |
+--------------------------------------------------------------------+
| Initiate a busy    | "A" sends a REQUEST "REQUEST" |                         |
| time request       | message to "B" and  |                         |
|                    | and "C"             |                         |
+--------------------------------------------------------------------+
| Reply to the busy  | "BUSY"|                     | "B" sends a REPLY "REPLY"     |
| request with busy  | "BUSY"|                     | message to "A" with     |
| time data          |                     | busy time data          |
+--------------------------------------------------------------------+


4.3.1     Request Busy Time

"A" sends a BUSY-"REQUEST" "BUSY-REQUEST" to "B" and "C" for busy time



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BEGIN:VCALENDAR
PRODID:-//ACME/DesktopCalendar//EN
METHOD:REQUEST
VERSION:2.0
BEGIN:VFREEBUSY
     ATTENDEE;ROLE=OWNER:Mailto:A@example.com
     ATTENDEE;ROLE=ATTENDEE;STATUS=ACCEPTED:Mailto:A@example.com
ORGANIZER:Mailto:A@example.com
ATTENDEE;ROLE=CHAIR:Mailto:A@example.com
ATTENDEE:Mailto:B@example.com
ATTENDEE:Mailto:C@example.com
DTSTAMP:19970613T190000Z
     DTSTART:19970701T080000-0700
     DTEND:19970701T200000-0700
     UID:www.acme.com-873970198738777@host.com
DTSTART:19970701T080000Z
DTEND:19970701T200000
UID:www.acme.com-873970198738777@example.com
END:VFREEBUSY
END:VCALENDAR


4.3.2     Reply To A Busy Time Request

"B" sends a "REPLY" method type of a "VFREEBUSY" calendar component to
"A"


BEGIN:VCALENDAR
PRODID:-//ACME/DesktopCalendar//EN
METHOD:REPLY
VERSION:2.0
BEGIN:VFREEBUSY
ORGANIZER:MAILTO:A@example.com
ATTENDEE:Mailto:B@example.com
     DTSTART:19970701T080000-0700
     DTEND:19970701T200000-0700
     UID:www.acme.com-873970198738777@host.com
     FREEBUSY:19970701T090000-0700/PT1H,19970701T140000-0700/PT30H
DTSTART:19970701T080000Z
DTEND:19970701T200000Z
UID:www.acme.com-873970198738777@example.com
FREEBUSY:19970701T090000Z/PT1H,19970701T140000Z/PT30H
DTSTAMP:19970613T190030Z
END:VFREEBUSY
END:VCALENDAR


   B

"B" is busy from 09:00 to 10:00 and from 14:00 to 14:30.


4.4 Recurring Event and Time Zone Examples


4.4.1     A Recurring Event Spanning Time Zones

This event describes a weekly phone conference. The "Attendees" are each
in a different time zone.


BEGIN:VCALENDAR

PRODID:-//ACME/DesktopCalendar//EN
     METHOD:REQUEST


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METHOD:REQUEST
VERSION:2.0

BEGIN:VTIMEZONE
     DAYLIGHT:TRUE
     DTSTART:19970406T200000-0800
     RRULE:FREQ=YEARLY;BYDAY=1SU;BYMONTH=4
     TZNAME:PDT
     TZOFFSET:-0700
     END:VTIMEZONE

     BEGIN:VTIMEZONE
     DAYLIGHT:FALSE
     DTSTART:19971026T200000-0700
TZID:America-SanJose
TZURL:http://zones.stds_r_us.net/tz/America-SanJose
LAST-MODIFIED:19870101T000000Z
BEGIN:STANDARD
DTSTART:19671029T020000
RRULE:FREQ=YEARLY;BYDAY=-1SU;BYMONTH=10
TZOFFSETFROM:-0700
TZOFFSETTO:-0800
TZNAME:PST
     TZOFFSET:-0800
END:STANDARD
BEGIN:DAYLIGHT
DTSTART:19870405T020000
RRULE:FREQ=YEARLY;BYDAY=1SU;BYMONTH=4
TZOFFSETFROM:-0800
TZOFFSETTO:-0700
TZNAME:PDT
END:DAYLIGHT
END:VTIMEZONE

BEGIN:VEVENT
     ATTENDEE;ROLE=OWNER;STATUS=ACCEPTED:Mailto:A@example.com
     ATTENDEE;RSVP=TRUE;EXPECT=REQUEST;TYPE=INDIVIDUAL:B@example.fr
     ATTENDEE;RSVP=TRUE;EXPECT=REQUEST;TYPE=INDIVIDUAL:c@example.jp
ORGANIZER:Mailto:A@example.com
ATTENDEE;ROLE=CHAIR;ATTSTAT=ACCEPTED;TYPE=INDIVIDUAL:A@example.COM
ATTENDEE;RSVP=TRUE;TYPE=INDIVIDUAL:B@example.fr
ATTENDEE;RSVP=TRUE;TYPE=INDIVIDUAL:c@example.jp
DTSTAMP:19970613T190030Z
     DTSTART:19970701T140000
     DTEND:19970701T150000
DTSTART;TZID=America-SanJose:19970701T140000
DTEND;TZID=America-SanJose:19970701T150000
RRULE:FREQ=WEEKLY;INTERVAL=20;WKST=SU;BYDAY=TU
     RDATE:19970910T140000
     EXDATE:19970909T140000
     EXDATE:19971028T150000
RDATE;TZID=America-SanJose:19970910T140000
EXDATE;TZID=America-SanJose:19970909T140000
EXDATE;TZID=America-SanJose:19971028T140000
SUMMARY:Weekly Phone Conference
     UID:www.acme.com-873970198738777@host.com
     SEQUENCE:0
     STATUS:CONFIRMED
     END:VEVENT

     END:VCALENDAR


   The "VTIMEZONE" components SHOULD appear in an iCalendar object
   containing recurring events. This is especially important if a
   recurring event has "Attendees" in different time zones. There MAY be
   multiple VTIMEZONE components in an iCalendar object, however, they
   MUST be used to define the same time zone. That is, there cannot be
   VTIMEZONE components describing both PST/PDT and EST/EDT at the
   component level in the same iCalendar object. Phone Conference
UID:www.acme.com-873970198738777@example.com
SEQUENCE:0
STATUS:CONFIRMED
END:VEVENT

END:VCALENDAR

The first two components of this iCalendar object are the time zone
components. The "DTSTART" date coincides with the first instance of the
RRULE property.

The recurring meeting is defined in a particular time zone, presumably
that of the originator. The client for each "Attendee" has the
responsibility of determining the recurrence time in the "Attendee's"
time zone.


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The repeating event starts on Tuesday, July 1, 1997 at 2:00pm. Since
   no time zone is specified in the "DTSTART" property, the time zone
   component of PDT applies to the start and end times. 2:00pm PDT.
"Attendee" B@example.fr is in France where the local time on this date


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is 7 hours later than PDT or 21:00. "Attendee" C@example.jp is in Japan
where local time is 9 hours ahead of than UTC or Wednesday, July 2 at
07:00. The event repeats weekly on Tuesdays (in PST/PDT). The "RRULE"
property results in 20 instances. The last instance falls on Tuesday,
November 11, 1997 2:00pm PST. The "RDATE" property adds another
instance: WED, 10-SEP-1997 21:00 GMT. 2:00 PM PST.

There are two exceptions to this recurring appointment. The first one
is:

TUE, 09-SEP-1997 21:00 GMT
TUE, 09-SEP-1997 14:00 PDT
WED, 10-SEP-1997 07:00 JDT

and the second is:

TUE, 28-OCT-1997 22:00 GMT
TUE, 28-OCT-1997 14:00 PST
WED, 29-OCT-1997 07:00 JST


4.4.2     Modify A Recurring Instance

In this example the "Organizer" issues a recurring meeting. Later the
"Organizer" changes an instance of the event by changing the "DTSTART"
property. Note the use of "RECURRENCE-ID" property and "SEQUENCE"
property in the second request.

Original Request:

BEGIN:VCALENDAR
METHOD:REQUEST
PRODID:-//RDU Software//NONSGML HandCal//EN
VERSION:2.0
BEGIN:VEVENT
     CREATED:19970526T083000
CREATED:19970526T083000Z
UID:guid-1@host1.com
SEQUENCE:0
RRULE:FREQ=MONTHLY;BYMONTHDAY=1;UNTIL=19980901T210000Z
     ATTENDEE;ROLE=OWNER:Mailto:A@example.com
     ATTENDEE;ROLE=ATTENDEE;STATUS=ACCEPTED:Mailto:A@example.com
     ATTENDEE;EXPECT=REQUEST:Mailto:B@example.com
     ATTENDEE;EXPECT=REQUEST:Mailto:C@example.com
     ATTENDEE;EXPECT=REQUEST:Mailto:D@example.com
ORGANIZER:Mailto:A@example.com
ATTENDEE;ROLE=CHAIR;ATTSTAT=ACCEPTED:Mailto:A@example.com
ATTENDEE:Mailto:B@example.com
ATTENDEE:Mailto:C@example.com
ATTENDEE:Mailto:D@example.com
DESCRIPTION:IETF-C&S Conference Call
CLASS:PUBLIC
SUMMARY:IETF Calendaring Working Group Meeting
DTSTART:19970601T210000Z
DTEND:19970601T220000Z
LOCATION:Conference Call
DTSTAMP:19970526T083000Z
STATUS:CONFIRMED
END:VEVENT
END:VCALENDAR


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The event request below is to change the time of a specific instance.
This changes the July 1st instance to July 3rd.

BEGIN:VCALENDAR
METHOD:REQUEST
PRODID:-//RDU Software//NONSGML HandCal//EN
VERSION:2.0
BEGIN:VEVENT
CREATED:19970526T083000Z
UID:guid-1@host1com
RECURRENCE-ID:19970701T210000Z
SEQUENCE:1
ORGANIZER:Mailto:A@example.com
ATTENDEE;ROLE=CHAIR;ATTSTAT=ACCEPTED:Mailto:A@example.com
ATTENDEE:Mailto:B@example.com
ATTENDEE:Mailto:C@example.com
ATTENDEE:Mailto:D@example.com
DESCRIPTION:IETF-C&S Conference Call
CLASS:PUBLIC
SUMMARY:IETF Calendaring Working Group Meeting
DTSTART:19970703T210000Z
DTEND:19970703T220000Z
LOCATION:Conference Call
DTSTAMP:19970626T093000Z
STATUS:CONFIRMED
END:VEVENT
END:VCALENDAR


4.4.3     Cancel an Instance

In this example the "Organizer" of a recurring event deletes the August
1st instance.


BEGIN:VCALENDAR
METHOD:CANCEL
PRODID:-//RDU Software//NONSGML HandCal//EN
VERSION:2.0
BEGIN:VEVENT
UID:guid-1@host1.com
ORGANIZER:Mailto:A@example.com
RECURRENCE-ID:19970801T210000Z
SEQUENCE:2
STATUS:CANCELLED
DTSTAMP:19970721T093000Z
END:VEVENT
END:VCALENDAR







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4.4.4     Cancel Recurring Event

In this example the "Organizer" wishes to cancel the entire recurring
event and any exceptions.

BEGIN:VCALENDAR
METHOD:CANCEL
PRODID:-//RDU Software//NONSGML HandCal//EN
VERSION:2.0
BEGIN:VEVENT
UID:guid-1@host1.com
ORGANIZER:Mailto:A@example.com
DTSTAMP:19970721T103000Z
SEQUENCE:2
END:VEVENT
END:VCALENDAR


4.4.5     Change All Future Instances

This example changes the meeting location from a conference call to
Seattle starting September 1 and extends to all future instances.


BEGIN:VCALENDAR
METHOD:REQUEST
PRODID:-//RDU Software//NONSGML HandCal//EN
VERSION:2.0
BEGIN:VEVENT
CREATED:19970526T083000Z
UID:guid-1@host1.com
RECURRENCE-ID;THISANDFUTURE:19970901T210000Z
SEQUENCE:3
ORGANIZER:Mailto:A@example.com
ATTENDEE;ROLE=CHAIR;ATTSTAT=ACCEPTED:Mailto:A@example.com
ATTENDEE;RSVP=TRUE:Mailto:B@example.com
ATTENDEE;RSVP=TRUE:Mailto:C@example.com
ATTENDEE;RSVP=TRUE:Mailto:D@example.com
DESCRIPTION:IETF-C&S Discussion
CLASS:PUBLIC
SUMMARY:IETF Calendaring Working Group Meeting
DTSTART:19970901T210000Z
DTEND:19970901T220000Z
LOCATION:Building 32, Microsoft, Seattle, WA
DTSTAMP:19970526T083000Z
STATUS:CONFIRMED
END:VEVENT
END:VCALENDAR


4.4.6     Add A New Instance To A Recurring Event

This example adds a one-time additional instance to the recurring event.
"Organizer" adds a second July meeting on the 15th.


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     DTSTAMP:19970526T083000
     STATUS:CONFIRMED
     END:VEVENT
     END:VCALENDAR


   The event request below is to change a time and create an exception.
   This creates an exception on July 3rd.                       March 13, 1998


BEGIN:VCALENDAR
     METHOD:REQUEST
METHOD:ADD
PRODID:-//RDU Software//NONSGML HandCal//EN
VERSION:2.0
BEGIN:VEVENT
     CREATED:19970526T083000
     UID:guid-1@host1com
     RECURRENCE-ID:19970701T210000Z
     SEQUENCE:1
     RRULE:FREQ=MONTHLY;BYMONTHDAY=1;UNTIL=19980901T210000Z
     ATTENDEE;ROLE=OWNER:Mailto:A@example.com
     ATTENDEE;ROLE=ATTENDEE;STATUS=ACCEPTED:Mailto:A@example.com
     ATTENDEE;EXPECT=REQUEST:Mailto:B@example.com
     ATTENDEE;EXPECT=REQUEST:Mailto:C@example.com
     ATTENDEE;EXPECT=REQUEST:Mailto:D@example.com
CREATED:19970526T083000Z
UID:123456789@host1.com
SEQUENCE:4
ORGANIZER:Mailto:A@example.com
ATTENDEE;ROLE=CHAIR;ATTSTAT=ACCEPTED:Mailto:A@example.com
ATTENDEE;RSVP=TRUE:Mailto:B@example.com
ATTENDEE;RSVP=TRUE:Mailto:C@example.com
ATTENDEE;RSVP=TRUE:Mailto:D@example.com
DESCRIPTION:IETF-C&S Conference Call
CLASS:PUBLIC
SUMMARY:IETF Calendaring Working Group Meeting
     DTSTART:19970703T210000Z
     DTEND:19970703T220000Z
DTSTART:19970715T210000Z
DTEND:19970715T220000Z
LOCATION:Conference Call
     DTSTAMP:19970626T093000
DTSTAMP:19970629T093000Z
STATUS:CONFIRMED
END:VEVENT
END:VCALENDAR


4.4.3     Cancel

4.4.7     Add A New Series of Instances To A Recurring Instance


   In Event

The scenario for this example the "Organizer" of a recurring event wishes to delete involves an instance. This is referred ongoing meeting, originally
set up to as an "exception" occur every Tuesday.  The "Organizer" later decides that the
meetings need to be on Tuesdays and Thursdays, but does not want to
reschedule the recurring
   event. entire meeting or lose any of the per-instance
information already collected.

The original event:

BEGIN:VCALENDAR
     METHOD:CANCEL
METHOD:REQUEST
PRODID:-//RDU Software//NONSGML HandCal//EN
VERSION:2.0
BEGIN:VEVENT
     UID:guid-1@host1.com
     RECURRENCE-ID:19970801T210000Z
     SEQUENCE:2
     DTSTAMP:19970721T093000
     STATUS:CANCELLED
UID:123456789@host1.com
SEQUENCE:0
RRULE:WKST=SU;BYDAY=TU;FREQ=WEEKLY
ORGANIZER:Mailto:A@example.com
ATTENDEE;ROLE=CHAIR;ATTSTAT=ACCEPTED:Mailto:A@example.com
ATTENDEE;RSVP=TRUE:Mailto:B@example.com
SUMMARY:Review Accounts
DTSTART:19980303T210000Z
DTEND:19980303T220000Z
LOCATION:The White Room
DTSTAMP:19980301T093000Z
STATUS:CONFIRMED
END:VEVENT
END:VCALENDAR



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     END:VCALENDAR


4.4.4     Cancel An Exception


   In                       March 13, 1998


The "Organizer" adds Thursdays to the following example, event:

BEGIN:VCALENDAR
METHOD:ADD
PRODID:-//RDU Software//NONSGML HandCal//EN
VERSION:2.0
BEGIN:VEVENT
UID:123456789@host1.com
SEQUENCE:7
RRULE:WKST=SU;BYDAY=TH;FREQ=WEEKLY
ORGANIZER:Mailto:A@example.com
ATTENDEE;ROLE=CHAIR;ATTSTAT=ACCEPTED:Mailto:A@example.com
ATTENDEE;RSVP=TRUE:Mailto:B@example.com
SUMMARY:Review Accounts
DTSTART:19980303T210000Z
DTEND:19980303T220000Z
DTSTAMP:19980303T193000Z
LOCATION:The Usual conference room
STATUS:CONFIRMED
END:VEVENT
END:VCALENDAR

Alternatively, if the "Organizer" has created an exception
   (as in 4.4.3) and now wishes to cancel it. In this case a "CANCEL"
   method is sent not concerned with per-instance
updates, the entire event can be rescheduled using a "REQUEST". This is
done by using the specific "RECURRENCE-ID", "UID" of the event to reschedule and including the
modified RRULE.


BEGIN:VCALENDAR
METHOD:ADD
PRODID:-//RDU Software//NONSGML HandCal//EN
VERSION:2.0
BEGIN:VEVENT
UID:123456789@host1.com
SEQUENCE:7
RRULE:WKST=SU;BYDAY=TU,TH;FREQ=WEEKLY
ORGANIZER:Mailto:A@example.com
ATTENDEE;ROLE=CHAIR;ATTSTAT=ACCEPTED:Mailto:A@example.com
ATTENDEE;RSVP=TRUE:Mailto:B@example.com
SUMMARY:Review Accounts
DTSTART:19980303T210000Z
DTEND:19980303T220000Z
DTSTAMP:19980303T193000Z
LOCATION:The White Room
STATUS:CONFIRMED
END:VEVENT
END:VCALENDAR

The next series of examples illustrate how an "Organizer" would respond
to a "REFRESH" submitted by an "Attendee" after a series of instance-
specific modifications. To convey all instance-specific changes, the
"Organizer" must provide the latest event description and the relevant
instances. The first three examples show the history including the



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initial "VEVENT" request and
   "SEQUENCE" properties of subsequent instance changes and finally the exception. This same sequence MAY be
   used to decline a previously accepted modification to a recurring
   event (as in 4.4.2).
"REFRESH".

Original Request:

BEGIN:VCALENDAR
     METHOD:CANCEL
METHOD:REQUEST
PRODID:-//RDU Software//NONSGML HandCal//EN
VERSION:2.0
BEGIN:VEVENT
     UID:guid-1@host1.com
     RECURRENCE-ID:19970801T210000Z
     SEQUENCE:2
     DTSTAMP:19970721T103000
     STATUS:CANCELLED
UID:123456789@host1.com
SEQUENCE:0
RDATE:19980304T180000Z
RDATE:19980311T180000Z
RDATE:19980318T180000Z
RDATE:19980325T180000Z
ORGANIZER:Mailto:A@example.com
ATTENDEE;ROLE=CHAIR;ATTSTAT=ACCEPTED:Mailto:A@example.com
ATTENDEE;RSVP=TRUE:Mailto:B@example.com
SUMMARY:Review Accounts
DTSTART:19980304T180000Z
DTEND:19980304T200000Z
DTSTAMP:19980303T193000Z
LOCATION:Conference Room A
STATUS:CONFIRMED
END:VEVENT
END:VCALENDAR


4.4.5     Cancel Recurring Event


   In this example the "Organizer" wishes to cancel the entire recurring
   event

Organizer changes 2nd instance Location and any child exceptions. Time:

BEGIN:VCALENDAR
     METHOD:CANCEL
METHOD:REQUEST
PRODID:-//RDU Software//NONSGML HandCal//EN
VERSION:2.0
BEGIN:VEVENT
     UID:guid-1@host1.com
     DTSTAMP:19970721T103000
     SEQUENCE:2
     STATUS:CANCELLED
UID:123456789@host1.com
SEQUENCE:1
RECURRENCE-ID:19980311T180000Z
ORGANIZER:Mailto:A@example.com
ATTENDEE;ROLE=CHAIR;ATTSTAT=ACCEPTED:Mailto:A@example.com
ATTENDEE;RSVP=TRUE:Mailto:B@example.com
SUMMARY:Review Accounts
DTSTART:19980311T160000Z
DTEND:19980304T180000Z
DTSTAMP:19980306T193000Z
LOCATION:The Small conference room
STATUS:CONFIRMED
END:VEVENT
END:VCALENDAR


4.4.6     Change All Future Instances


   This example changes

Organizer adds a 4th instance of the meeting location from a conference call to
   Seattle starting Sept 1 and extends to all future instances. using the "ADD" method

BEGIN:VCALENDAR
     METHOD:REQUEST
METHOD:ADD


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PRODID:-//RDU Software//NONSGML HandCal//EN
VERSION:2.0
BEGIN:VEVENT
     CREATED:19970526T083000
     UID:guid-1@host1.com
     RECURRENCE-ID;THISANDFUTURE:19970901T210000Z
     SEQUENCE:3
     RRULE:FREQ=MONTHLY;BYMONTHDAY=1;UNTIL=19980901T210000Z
     ATTENDEE;ROLE=OWNER:Mailto:A@example.com
     ATTENDEE;ROLE=ATTENDEE;STATUS=ACCEPTED:Mailto:A@example.com
     ATTENDEE;EXPECT=REQUEST:Mailto:B@example.com
     ATTENDEE;EXPECT=REQUEST:Mailto:C@example.com
     ATTENDEE;EXPECT=REQUEST:Mailto:D@example.com
     DESCRIPTION:IETF-C&S Conference Call
     CLASS:PUBLIC
     SUMMARY:IETF Calendaring Working Group Meeting
     DTSTART:19970901T210000Z [SS2][SS3]
     DTEND:19970901T220000Z
     LOCATION:Building 32, Microsoft, Seattle, WA
     DTSTAMP:19970526T083000
UID:123456789@host1.com
SEQUENCE:2
ORGANIZER:Mailto:A@example.com
ATTENDEE;ROLE=CHAIR;ATTSTAT=ACCEPTED:Mailto:A@example.com
ATTENDEE;RSVP=TRUE:Mailto:B@example.com
SUMMARY:Review Accounts
DTSTART:19980315T180000Z
DTEND:19980315T200000Z
DTSTAMP:19980307T193000Z
LOCATION:Conference Room A
STATUS:CONFIRMED
END:VEVENT
END:VCALENDAR


4.4.7     Add A New Instance To A Recurring Event


   This example adds

If "B" requests a one-time additional instance "REFRESH", "A" responds with the following to capture
all instance-specific data. In this case both the recurring
   event. "Organizer" adds a second July meeting on initial request and an
additional "VEVENT" that specifies the 15th. instance-specific data are
included. Because these are both of the same type (they are both
"VEVENTS"), they can be conveyed in the same iCalendar object.

BEGIN:VCALENDAR
METHOD:REQUEST
PRODID:-//RDU Software//NONSGML HandCal//EN
VERSION:2.0
BEGIN:VEVENT
     CREATED:19970526T083000
     UID:guid-1@host1.com
     RECURRENCE-ID:19970715T210000Z
     SEQUENCE:4
     RRULE:FREQ=MONTHLY;BYMONTHDAY=1;UNTIL=19980901T210000Z
     RDATE;VALUE=PERIOD:19970715T210000Z/19970715T220000Z
     ATTENDEE;ROLE=OWNER:Mailto:A@example.com
     ATTENDEE;ROLE=ATTENDEE;STATUS=ACCEPTED:Mailto:A@example.com
     ATTENDEE;EXPECT=REQUEST:Mailto:B@example.com
     ATTENDEE;EXPECT=REQUEST:Mailto:C@example.com
     ATTENDEE;EXPECT=REQUEST:Mailto:D@example.com
     DESCRIPTION:IETF-C&S Conference Call
     CLASS:PUBLIC
     SUMMARY:IETF Calendaring Working Group Meeting
     DTSTART:19970715T210000Z
     DTEND:19970715T220000Z
UID:123456789@host1.com
SEQUENCE:3
RDATE:19980304T180000Z
RDATE:19980318T180000Z
RDATE:19980315T180000Z
Error! Bookmark not defined.
ORGANIZER:Mailto:A@example.com
ATTENDEE;ROLE=CHAIR;ATTSTAT=ACCEPTED:Mailto:A@example.com
ATTENDEE;RSVP=TRUE:Mailto:B@example.com
SUMMARY:Review Accounts
DTSTART:19980304T180000Z
DTEND:19980304T200000Z
DTSTAMP:19980303T193000Z
LOCATION:Conference Call
     DTSTAMP:19970629T093000 Room A
STATUS:CONFIRMED
END:VEVENT

BEGIN:VEVENT
Error! Bookmark not defined.
SEQUENCE:3
RECURRENCE-ID:19980311T160000Z
Error! Bookmark not defined.
ATTENDEE;ROLE=CHAIR;Error! Bookmark not defined.
ATTENDEE;Error! Bookmark not defined.
SUMMARY:Review Accounts
DTSTART:19980311T160000Z


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DTEND:19980304T180000Z
DTSTAMP:19980306T193000Z
LOCATION:The Small conference room
STATUS:CONFIRMED
END:VEVENT

END:VCALENDAR


4.4.8     Counter An Instance Of A Recurring Event

In this example one of the "Attendees" counters the "DTSTART" property
of the proposed second July meeting.


BEGIN:VCALENDAR
METHOD:COUNTER
PRODID:-//RDU Software//NONSGML HandCal//EN
VERSION:2.0
BEGIN:VEVENT
     CREATED:19970526T083000
CREATED:19970526T083000Z
UID:guid-1@host1.com
RECURRENCE-ID:19970715T210000Z
SEQUENCE:4
     RRULE:FREQ=MONTHLY;BYMONTHDAY=1;UNTIL=19980901T210000Z
     ATTENDEE;ROLE=OWNER:Mailto:A@example.com
     ATTENDEE;ROLE=ATTENDEE;STATUS=ACCEPTED:Mailto:A@example.com
     ATTENDEE;EXPECT=REQUEST:Mailto:B@example.com
     ATTENDEE;EXPECT=REQUEST:Mailto:C@example.com
     ATTENDEE;EXPECT=REQUEST:Mailto:D@example.com
ORGANIZER:Mailto:A@example.com
ATTENDEE;ROLE=CHAIR;RSVP=TRUE:Mailto:A@example.com
ATTENDEE;RSVP=TRUE:Mailto:B@example.com
ATTENDEE;RSVP=TRUE:Mailto:C@example.com
ATTENDEE;RSVP=TRUE:Mailto:D@example.com
DESCRIPTION:IETF-C&S Conference Call
CLASS:PUBLIC
SUMMARY:IETF Calendaring Working Group Meeting
DTSTART:19970715T220000Z
DTEND:19970715T230000Z
LOCATION:Conference Call
COMMENT:May we bump this by an hour? I have a conflict
     DTSTAMP:19970629T094000
DTSTAMP:19970629T094000Z
END:VEVENT
END:VCALENDAR


4.4.9     Error Reply To A request Request

The following example illustrates a scenario where a meeting is
   proposed that contains a property that a meeting is not supported (in this
   case, the "RRULE" property). proposed
containing an unsupported property and a bad property.

Original Request: Request

BEGIN:VCALENDAR
METHOD:REQUEST
PRODID:-//RDU Software//NONSGML HandCal//EN
VERSION:2.0
BEGIN:VEVENT
     CREATED:19970526T083000
     UID:guid-1@host1.com
CREATED:19970526T083000Z


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UID:guid-1@host1.com
SEQUENCE:0
RRULE:FREQ=MONTHLY;BYMONTHDAY=1
     ATTENDEE;ROLE=OWNER:Mailto:A@example.com
     ATTENDEE;ROLE=ATTENDEE;STATUS=ACCEPTED:Mailto:A@example.com
     ATTENDEE;EXPECT=REQUEST:Mailto:B@example.com
     ATTENDEE;EXPECT=REQUEST:Mailto:C@example.com
     ATTENDEE;EXPECT=REQUEST:Mailto:D@example.com
ORGANIZER:Mailto:A@example.com
ATTENDEE;ROLE=CHAIR:Mailto:A@example.com
ATTENDEE;RSVP=TRUE:Mailto:B@example.com
ATTENDEE;RSVP=TRUE:Mailto:C@example.com
ATTENDEE;RSVP=TRUE:Mailto:D@example.com
DESCRIPTION:IETF-C&S Conference Call
CLASS:PUBLIC
SUMMARY:IETF Calendaring Working Group Meeting
DTSTART:19970601T210000Z
DTEND:19970601T220000Z
     DTSTAMP:19970602T094000
DTSTAMP:19970602T094000Z
LOCATION:Conference Call
STATUS:CONFIRMED
FOO:BAR
END:VEVENT
END:VCALENDAR

Response from "B" to indicate that RRULE is not supported: supported and an
unrecognized property was encountered


BEGIN:VCALENDAR
PRODID:-//RDU Software//NONSGML HandCal//EN
METHOD:REPLY
VERSION:2.0
BEGIN:VEVENT
ORGANIZER:Mailto:A@example.com
ATTENDEE:Mailto:B@example.com
REQUEST-STATUS:2.8;Repeating event ignored. Scheduled as a single
  event;RRULE
REQUEST-STATUS:3.0;Invalid Property Name;FOO
UID:guid-1@host1.com
SEQUENCE:0
     DTSTAMP:19970603T094000
DTSTAMP:19970603T094000Z
END:VEVENT
END:VCALENDAR


4.5 Group To-do Examples

Individual "A" creates a group task in which individuals "A", "B", "C"
and "D" will participate. Individual "B" confirms acceptance of the
task. Individual "C" declines the task. Individual "D" tentatively
accepts the task. The following table illustrates the sequence of
messages that would be exchanged between these individuals. Individual
"A" then issues a "REFRESH" "REQUEST" method to obtain the status of the to-do
from each participant. The response indicates the individual
"Attendee's" completion status. The table below illustrates the message
flow.




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+--------------------------------------------------------------------+
| Action             |  "Organizer"        | Attendee                |
+--------------------------------------------------------------------+
| Initiate a to-do   | "A" sends a REQUEST |                         |
| request            | message to "B", "C",|                         |
|                    | and "D"             |                         |


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+--------------------------------------------------------------------+
| Accept the to-do   |                     | "B" sends a REPLY "REPLY"     |
| request            |                     | message to "A" with its |
|                    |                     | ATTENDEE STATUS para- "attstat" paramater     |
|                    |                     | set to "ACCEPTED". "accepted".      |
+--------------------------------------------------------------------+
| Decline the to-do  |                     | "C" sends a REPLY       |
| request            |                     | message to "A" with its |
|                    |                     | ATTENDEE STATUS para- "attstat" parameter     |
|                    |                     | set to "DECLINED". "declined".      |
+--------------------------------------------------------------------+
| Tentatively accept |                     | "D" sends a REPLY       |
| the to-do request  |                     | message to "A" with its |
|                    |                     | ATTENDEE STATUS para- "attstat" parameter     |
|                    |                     | set to "TENTATIVE". "tentative".     |
+--------------------------------------------------------------------+
| Check attendee     | "A" sends a REFRESH REQUEST |                         |
| completion status  | message to "B" and  |                         |
|                    | "C" with current    |                         |
|                    | information.        |                         |
+--------------------------------------------------------------------+
| Attendee indicates |                     | "B" sends a REPLY "REPLY"     |
| percent complete   |                     | message indicating      |
|                    |                     | percent complete        |
+--------------------------------------------------------------------+
| Attendee indicates |                     | "C" sends a REPLY "REPLY"     |
| completion         |                     | message indicating      |
|                    |                     | completion              |
+--------------------------------------------------------------------+


4.5.1     A VTODO Request

A sample "REQUEST" with for a "VTODO" calendar component that "A" sends
to "B", "C", and "D".


BEGIN:VCALENDAR
PRODID:-//ACME/DesktopCalendar//EN
METHOD:REQUEST
VERSION:2.0
BEGIN:VTODO
     ATTENDEE;ROLE=OWNER:Mailto:A@example.com
     ATTENDEE;ROLE=ATTENDEE;STATUS=ACCEPTED:Mailto:A@example.com
     ATTENDEE;RSVP=TRUE;EXPECT=REQUEST;TYPE=INDIVIDUAL:Mailto:B@example.
com
     ATTENDEE;RSVP=TRUE;EXPECT=REQUEST;TYPE=INDIVIDUAL:Mailto:C@example.
com
     ATTENDEE;RSVP=TRUE;EXPECT=REQUEST;TYPE=INDIVIDUAL:Mailto:D@example.
com
     DTSTART:19970701T100000-0700
     DUE:19970722T100000-0700
     SUMMARY:Create the requirements document
     UID:www.acme.com-873970198738777-00@host.com
ORGANIZER:Mailto:A@example.com
ATTENDEE;ROLE=CHAIR:Mailto:A@example.com
ATTENDEE;RSVP=TRUE:B@example.com
ATTENDEE;RSVP=TRUE:Mailto:C@example.com
ATTENDEE;RSVP=TRUE:Mailto:D@example.com
DTSTART:19970701T170000Z


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DUE:19970722T170000Z
SUMMARY:Create the requirements document
UID:www.acme.com-873970198738777-00@example.com
SEQUENCE:0
DTSTAMP:19970717T200000Z
     STATUS:CONFIRMED
STATUS:Needs Action
END:VTODO
END:VCALENDAR


4.5.2     A VTODO Reply

Attendee "B" accepts the meeting.

BEGIN:VCALENDAR
PRODID:-//ACME/DesktopCalendar//EN
METHOD:REPLY
VERSION:2.0
BEGIN:VTODO
     ATTENDEE;STATUS=ACCEPTED:Mailto:B@example.com
     UID:www.acme.com-873970198738777-00@host.com
ORGANIZER:Mailto:A@example.com
ATTENDEE;ATTSTAT=ACCEPTED:Mailto:B@example.com
UID:www.acme.com-873970198738777-00@example.com
COMMENT:I'll send you my input by e-mail
SEQUENCE:0
DTSTAMP:19970717T203000Z
REQUEST-STATUS:2.0;Success
END:VTODO
END:VCALENDAR

"B" could have declined the meeting TODO or indicated tentative acceptance by
setting the "ATTENDEE;STATUS=" "attstat" property parameter sequence to
   DECLINED "declined" or TENTATIVE,
"tentative", respectively.


4.5.3     A VTODO Refresh Request for Updated Status

"A" requests status from all "Attendees".


BEGIN:VCALENDAR
PRODID:-//ACME/DesktopCalendar//EN
     METHOD:REFRESH
METHOD:REQUEST
VERSION:2.0
BEGIN:VTODO
     ATTENDEE;ROLE=OWNER:Mailto:A@example.com
     ATTENDEE;ROLE=ATTENDEE;STATUS=ACCEPTED:Mailto:A@example.com
     ATTENDEE;RSVP=TRUE;EXPECT=REQUEST;TYPE=INDIVIDUAL:Mailto:B@example.
com
     ATTENDEE;RSVP=TRUE;EXPECT=REQUEST;TYPE=INDIVIDUAL:Mailto:C@example.
com
     ATTENDEE;RSVP=TRUE;EXPECT=REQUEST;TYPE=INDIVIDUAL:Mailto:D@example.
com
     UID:www.acme.com-873970198738777-00@host.com
ORGANIZER:Mailto:A@example.com
ATTENDEE;ROLE=CHAIR:Mailto:A@example.com
ATTENDEE;RSVP=TRUE;TYPE=INDIVIDUAL:Mailto:B@example.com
ATTENDEE;RSVP=TRUE;TYPE=INDIVIDUAL:Mailto:C@example.com
ATTENDEE;RSVP=TRUE;TYPE=INDIVIDUAL:Mailto:D@example.com
UID:www.acme.com-873970198738777-00@example.com
SEQUENCE:0
STATUS:IN-PROCESS
DTSTAMP:19970717T230000Z
END:VTODO
     END:VCALENDAR


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END:VCALENDAR


4.5.4     A Refresh Reply: Percent-Complete

A reply indicating that the task in being worked on and that "B" is 75% complete
with "B's" part of the assignment.

BEGIN:VCALENDAR
PRODID:-//ACME/DesktopCalendar//EN
METHOD:REPLY
VERSION:2.0
BEGIN:VTODO
     ATTENDEE;STATUS=IN-PROCESS:Mailto:B@example.com
ORGANIZER:MAILTO:A@example.com
ATTENDEE;ATTSTAT=IN-PROCESS:Mailto:B@example.com
PERCENT-COMPLETE:75
     UID:www.acme.com-873970198738777-00@host.com
UID:www.acme.com-873970198738777-00@example.com
DTSTAMP:19970717T233000Z
SEQUENCE:0
END:VTODO
END:VCALENDAR


4.5.5     A Refresh Reply: Completed

A reply indicating that "C" finished with completed "C's" part of the assignment.


BEGIN:VCALENDAR
PRODID:-//ACME/DesktopCalendar//EN
METHOD:REPLY
VERSION:2.0
BEGIN:VTODO
     ATTENDEE;STATUS=COMPLETED:Mailto:C@example.com
     UID:www.acme.com-873970198738777-00@host.com
ORGANIZER:MAILTO:A@example.com
ATTENDEE;ATTSTAT=COMPLETED:Mailto:C@example.com
UID:www.acme.com-873970198738777-00@example.com
DTSTAMP:19970717T233000Z
SEQUENCE:0
END:VTODO
END:VCALENDAR


4.5.6     An Updated VTODO Request


   Owner

Organizer "A" resends the "VTODO" calendar component. "A" set's sets the
overall completion for the to-do at 40%.


BEGIN:VCALENDAR
PRODID:-//ACME/DesktopCalendar//EN
METHOD:REQUEST
VERSION:2.0
BEGIN:VTODO
     ATTENDEE;ROLE=OWNER:Mailto:A@example.com
     ATTENDEE;ROLE=ATTENDEE;STATUS=ACCEPTED:Mailto:A@example.com
     ATTENDEE;STATUS=ACCEPTED;TYPE=INDIVIDUAL:Mailto:B@example.com
     ATTENDEE;STATUS=COMPLETED;TYPE=INDIVIDUAL:Mailto:C@example.com
ORGANIZER:Mailto:A@example.com


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     ATTENDEE;STATUS=TENTATIVE;TYPE=INDIVIDUAL:Mailto:D@example.com                       March 13, 1998


ATTENDEE;ROLE=CHAIR;ATTSTAT=ACCEPTED:Mailto:A@example.com
ATTENDEE;ATTSTAT=ACCEPTED;TYPE=INDIVIDUAL:Mailto:B@example.com
ATTENDEE;ATTSTAT=COMPLETED;TYPE=INDIVIDUAL:Mailto:C@example.com
ATTENDEE;ATTSTAT=IN-PROCESS;TYPE=INDIVIDUAL:Mailto:D@example.com
DTSTART:19970701T100000-0700
DUE:19970722T100000-0700
SUMMARY:Create the requirements document
     UID:www.acme.com-873970198738777-00@host.com
UID:www.acme.com-873970198738777-00@example.com
SEQUENCE:1
DTSTAMP:19970718T100000Z
STATUS:IN-PROGRESS
PERCENT-COMPLETE:40
END:VTODO
END:VCALENDAR


4.5.7     A     Recurring VTODOs

The following examples relate to recurring "VTODO" calendar components.


4.5.7.1   Request for a Recurring VTODO

In this example "A" sends a recurring "VTODO" calendar component to "B"
and "C".


BEGIN:VCALENDAR
PRODID:-//ACME/DesktopCalendar//EN
METHOD:REQUEST
VERSION:2.0
BEGIN:VTODO
     ATTENDEE;ROLE=OWNER:Mailto:A@example.com
     ATTENDEE;ROLE=ATTENDEE;STATUS=ACCEPTED:Mailto:A@example.com
     ATTENDEE;RSVP=TRUE;EXPECT=REQUEST;TYPE=INDIVIDUAL:Mailto:B@example.
com
     ATTENDEE;RSVP=TRUE;EXPECT=REQUEST;TYPE=INDIVIDUAL:Mailto:C@example.
com
ORGANIZER:Mailto:A@example.com
ATTENDEE;ROLE=CHAIR:Mailto:A@example.com
ATTENDEE;RSVP=TRUE;TYPE=INDIVIDUAL:Mailto:B@example.com
ATTENDEE;RSVP=TRUE;TYPE=INDIVIDUAL:Mailto:C@example.com
RRULE:FREQ=MONTHLY;COUNT=10;BYDAY=1FR
DTSTART:19980101T100000-0700
DUE:19980103T100000-0700
SUMMARY:Send Status Reports to Area Managers
     UID:www.acme.com-873970198738777-00@host.com
UID:www.acme.com-873970198738777-00@example.com
SEQUENCE:0
DTSTAMP:19970717T200000Z
     STATUS:CONFIRMED
STATUS:NEEDS ACTION
END:VTODO
END:VCALENDAR


4.5.7.2   Calculating due dates in recurring VTODOs

The due date in a recurring "VTODO" calendar component is either a fixed
interval specified in the "REQUEST" method or specified
   specifically using the
"RECURRENCE-ID" property. The former is


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each of the start of each recurring instance. Hence, if the initial
"VTODO" calendar component specifies a "DTSTART" property value of
"19970701T190000Z" and a "DUE" property value of "19970801T190000Z" the
interval of one day which could be is applied to each recurring instance of the
"VTODO" calendar component. component to determine the "DUE" date of the instance.


4.5.7.3   Replying to an instance of a recurring VTODO

In this example "B" updates "A" on a single instance of the "VTODO"
calendar component.


BEGIN:VCALENDAR
PRODID:-//ACME/DesktopCalendar//EN
METHOD:REPLY
VERSION:2.0
BEGIN:VTODO
     ATTENDEE;STATUS=IN-PROCESS:Mailto:B@example.com
ATTENDEE;ATTSTAT=IN-PROCESS:Mailto:B@example.com
PERCENT-COMPLETE:75
     UID:www.acme.com-873970198738777-00@host.com
UID:www.acme.com-873970198738777-00@example.com
DTSTAMP:19970717T233000Z
     RECURRENCE-ID:19980101T100000-0700
     SEQUENCE:0
RECURRENCE-ID:19980101T170000Z
SEQUENCE:1
END:VTODO
END:VCALENDAR


4.6 Journal Examples

The iCalendar object below describes a single journal entry for October
2, 1997. The "RELATED-TO" property references the phone conference event
for which minutes were taken.


BEGIN:VCALENDAR
PROFILE:PUBLISH
PRODID:-//ACME/DesktopCalendar//EN
VERSION:2.0
BEGIN:VJOURNAL
DTSTART:19971002T200000Z
SUMMARY:Phone conference minutes
DESCRIPTION:The editors meeting was held on October 1, 1997.
  Details are in the attached document.
     UID:0981234-1234234-2410@host.com
     RELATED-TO:0981234-1234234-2402-35@host.com
UID:0981234-1234234-2410@example.com
RELATED-TO:0981234-1234234-2402-35@example.com
ATTACH:ftp\://ftp.example.com/pub/ed/minutes100197.txt
END:VJOURNAL
END:VCALENDAR







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4.7 Other Examples


4.7.1     Event Refresh

Refresh the event with "UID" property value of "guid-1-
   12345@host1.com": "guid-1-12345@host1.com":


BEGIN:VCALENDAR
PRODID:-//RDU Software//NONSGML HandCal//EN
METHOD:REFRESH
VERSION:2.0
BEGIN:VEVENT
     ATTENDEE;ROLE=OWNER:Mailto:A@example.com
     ATTENDEE;ROLE=ATTENDEE;STATUS=ACCEPTED:Mailto:A@example.com
     ATTENDEE;EXPECT=REQUEST:Mailto:B@example.com
     ATTENDEE;EXPECT=REQUEST:Mailto:C@example.com
     ATTENDEE;EXPECT=REQUEST:Mailto:D@example.com
ORGANIZER:Mailto:A@example.com
ATTENDEE;ROLE=CHAIR;ATTSTAT=ACCEPTED:Mailto:A@example.com
ATTENDEE:Mailto:B@example.com
ATTENDEE:Mailto:C@example.com
ATTENDEE:Mailto:D@example.com
UID: guid-1-12345@host1.com
DTSTAMP:19970603T094000
END:VEVENT
END:VCALENDAR

4.7.2     Bad RECURRENCE-ID

If an "Attendee" receives a request that references a "RECURRENCE-ID"
property that can not cannot be found, the "Attendee" SHOULD send a "REFRESH"
method back to the "Organizer" for the latest copy of the event.


+--------------------------------------------------------------------+
| Action             |  "Organizer"        | Attendee                |
+--------------------------------------------------------------------+
| Update an instance | "A" sends a REQUEST |  "REQUEST"|                         |
| request            | message to "B"      |                         |
+--------------------------------------------------------------------+
| Attendee requests  |                     | "B" sends a REFRESH "REFRESH"   |
| refresh because    |                     | message to "A"          |
| RecurrenceID was   | "RECURRENCE-ID" was|                     |                         |
| not found          |                     |                         |
+--------------------------------------------------------------------+
| Refresh the entire | "A" sends the       |                         |
| Event              | latest copy of the  |                         |
|                    | Event to "B"        |                         |
+--------------------------------------------------------------------+
| Attendee handles   |                     | "B" updates to the      |
| the request and    |                     | latest copy of the      |
| updates the        |                     | meeting.                |
| instance           |                     |                         |
+--------------------------------------------------------------------+

Request from "A":




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   Request from "A":                       March 13, 1998


BEGIN:VCALENDAR
METHOD:REQUEST
PRODID:-//RDU Software//NONSGML HandCal//EN
VERSION:2.0
BEGIN:VEVENT
UID:acme-12345@host1.com
SEQUENCE:3
RRULE:FREQ=WEEKLY
RDATE;VALUE=PERIOD:19970819T210000Z/199700819T220000Z
     ATTENDEE;ROLE=OWNER:Mailto:A@example.com
     ATTENDEE;ROLE=ATTENDEE;STATUS=ACCEPTED:Mailto:A@example.com
     ATTENDEE;EXPECT=REQUEST:Mailto:B@example.com
ORGANIZER:Mailto:A@example.com
ATTENDEE;ROLE=CHAIR;ATTSTAT=ACCEPTED:Mailto:A@example.com
ATTENDEE:Mailto:B@example.com
DESCRIPTION:IETF-C&S Conference Call
SUMMARY:IETF Calendaring Working Group Meeting
DTSTART:19970801T210000Z
DTEND:19970801T220000Z
DTSTAMP:19970726T083000
STATUS:CONFIRMED
END:VEVENT
END:VCALENDAR

"B" has the event with "UID" property"acme-12345@host1.com" property "acme-12345@host1.com" but the
"SEQUENCE" property value is "1" and the event does not have an instance
at the specified recurrence time. This means that the
   "Owner" is either adding a new instance or that the new instance was
   added when "SEQUENCE" property value "2" of the event was generated.
   In either case, "B" has missed one
update and needs a new copy of the event.


BEGIN:VCALENDAR
PRODID:-//RDU Software//NONSGML HandCal//EN
METHOD:REFRESH
VERSION:2.0
BEGIN:VEVENT
     ATTENDEE;ROLE=OWNER:Mailto:A@example.com
     ATTENDEE;ROLE=ATTENDEE;STATUS=ACCEPTED:Mailto:A@example.com
     ATTENDEE;EXPECT=REQUEST:Mailto:B@example.com
ORGANIZER:Mailto:A@example.com
ATTENDEE;ATTSTAT=ACCEPTED:Mailto:B@example.com
UID:acme-12345@host1.com
DTSTAMP:19970603T094000
END:VEVENT
END:VCALENDAR


5  Application Protocol Fallbacks


5.1 Partial Implementation

Applications that support this memo are not required to support the
entire protocol. The following describes how methods and properties
SHOULD "fallback" in applications that do not support the complete



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protocol. If a method or property is not addressed in this section, it MAY
may be ignored.






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5.1.1     Event-Related Fallbacks


Method           Fallback
--------------   -----------------------------------------------------
PUBLISH          Required.
CANCEL           Required.
REQUEST          PUBLISH
REPLY            Required.
ADD              Required.
DELEGATE         Reply with Not Supported.
REQUEST          Reply with Not Supported.
REPLY            Reply with Not Supported.
COUNTER          Reply with Not Supported
DECLINECOUNTER   Required if EVENT-COUNTER is implemented; otherwise
                 reply with Not Supported.

iCalendar
Property         Fallback
--------------   -----------------------------------------------------
CALSCALE         Ignore; assume GREGORIAN.
GEO              Ignore.
PRODID           Ignore.
METHOD           Required as described in the Method list above.
SOURCE           Ignore
NAME             Ignore.
VERSION          Ignore.

Event-Related
Components       Fallback
--------------   -----------------------------------------------------
VFREEBUSY        Reply with Not Supported.
VALARM           Reply with Not Supported.
VTIMEZONE        Required if RRULE or RDATE is implemented; otherwise
                 ignore and use local time.

Component
Property         Fallback
--------------   -----------------------------------------------------
ATTACH           Ignore.
ATTENDEE         Required if EVENT-REQUEST is not implemented;
                 otherwise reply with Not Supported.
CATEGORIES       Required if in VALARM and VALARM is implemented,
                 otherwise ignore.       Ignore.
CLASS            Ignore.
COMMENT          Ignore.
COMPLETED        Ignore.
CREATED          Ignore.
DAYLIGHT         Required if VTIMEZONE is implemented; otherwise
                 Ignore.
DESCRIPTION      Required.
DELEGATED-FROM   Required if EVENT-DELEGATE is implemented; otherwise


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                 Ignore.
DELEGATED-TO     Required if EVENT-DELEGATE is implemented; otherwise
                 Ignore.


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DUE              Ignore.
DURATION         Reply with Not Supported.
DTSTAMP          Required.
DTSTART          Required.
DTEND            Required.
EXDATE           Ignore.
EXRULE           Ignore.
FREEBUSY         Reply with Not Supported.
LAST-MODIFIED    Ignore.
LOCATION         Required.
PRIORITY         Ignore.
RELATED-TO       Ignore.
RDATE            Ignore. If implemented, VTIMEZONE MUST also be
                 implemented.
RRULE            Ignore. The first instance occurs on the DTStart
                 property.
RECURRENCE-ID    Required if RRULE is implemented; otherwise Ignore.
REQUEST-STATUS   Required.
RESOURCES        Ignore.
SEQUENCE         Required.
STATUS           Ignore.
SUMMARY          Ignore.
TRANSP           Required if FREEBUSY is implemented; otherwise Ignore.
TZNAME           Required if VTIMEZONE is implemented; otherwise
                 Ignore.
TZOFFSET         Required if VTIMEZONE is implemented; otherwise
                 Ignore.
URL              Ignore.
UID              Required.
X-               Ignore.


5.1.2     To-Do-Related Fallbacks


Method           Fallback
--------------   -----------------------------------------------------
PUBLISH          Required.
CANCEL           Required.
ADD              Required.
REQUEST          TODO-PUBLISH          TODO-PUBLISH.
REPLY            Required.

iCalendar
Property         Fallback
--------------   -----------------------------------------------------
CALSCALE         Ignore; assume GREGORIAN.
GEO              Ignore.
PRODID           Ignore.
METHOD           Required as described in the Method list above.
SOURCE           Ignore
NAME             Ignore.
VERSION          Ignore.



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VERSION          Ignore.                       March 13, 1998


To-Do-Related
Components       Fallback
--------------   -----------------------------------------------------
VALARM           Reply with Not Supported.
VTIMEZONE        Required if RRULE or RDATE is implemented;
                 otherwise ignore and use local time.

Component
Property         Fallback
--------------   -----------------------------------------------------
CALSCALE         Ignore; assume GREGORIAN.
GEO              Ignore.
PRODID           Ignore.
PROFILE          Required as described in the Method list above.
SOURCE           Ignore           Ignore.
NAME             Ignore.
VERSION          Assume "2.0".
Property         Fallback
ATTACH           Ignore.
ATTENDEE         Required if REQUEST is not implemented; otherwise
                 ignore.
CATEGORIES       Ignore.
CLASS            Ignore.
COMMENT          Ignore.
COMPLETED        Required.
CREATED          Ignore.
DAYLIGHT         Required if VTIMEZONE is implemented; otherwise
                 ignore.
DESCRIPTION      Required.
DUE              Required.
DURATION         Ignore. Reply with Not Supported.
DTSTAMP          Required.
DTSTART          Required.
EXDATE           Ignore. Reply with Not Supported.
EXRULE           Ignore. Reply with Not Supported.
LAST-MODIFIED    Ignore.
LOCATION         Ignore.
PERCENT-COMPLETE Ignore Ignore.
PRIORITY         Required.
RELATED-TO       Ignore.
RDATE            Ignore. If implemented, VTIMEZONE MUST also be
                 implemented.
RRULE            Ignore. The first instance occurs on the DTStart DTSTART
                 property.
RESOURCES        Ignore.
SEQUENCE         Required.
STATUS           Required.
SUMMARY          Ignore.
TRANSP           Required if FREEBUSY is implemented; otherwise Ignore. ignore.
TZNAME           Required if VTIMEZONE is implemented; otherwise
                 Ignore.
                 ignore.
TZOFFSET         Required if VTIMEZONE is implemented; otherwise
                 ignore.
URL              Ignore.


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                 Ignore.
URL              Ignore.                       March 13, 1998


UID              Required.
X-               Ignore.


5.1.3     Journal-Related Fallbacks


Method           Fallback
--------------   -----------------------------------------------------
PUBLISH          Implementations MAY ignore the profile type. The
                 REQUEST-STATUS "302;Request not Not supported" MUST be
                 returned.
CANCEL           Implementations MAY ignore the profile type. The
                 REQUEST-STATUS "302;Request not Not supported" MUST be
                 returned.
REFRESH
ADD              Implementations MAY ignore the profile type. The
                 REQUEST-STATUS "302;Request not Not supported" MUST be
                 returned.

iCalendar
Property         Fallback
--------------   -----------------------------------------------------
CALSCALE         Ignore; assume GREGORIAN.
GEO              Ignore.
PRODID           Ignore.
METHOD           Required as described in the Method list above.
SOURCE           Ignore
NAME             Ignore.
VERSION          Ignore.

Journal-Related
Components       Fallback
--------------   -----------------------------------------------------
VTIMEZONE        Required if RRULE or RDATE is implemented; otherwise
                 ignore and use local time.
CALSCALE         Ignore; assume GREGORIAN.
GEO              Ignore.
PRODID           Ignore.
METHOD           Required as described in the Method section above.
SOURCE           Ignore
NAME             Ignore.
VERSION          Assume "2.0".

Component
Property         Fallback
--------------   -----------------------------------------------------
ATTACH           Ignore.
ATTENDEE         Required if JOURNAL-REQUEST is implemented; otherwise
                 ignore.
CATEGORIES       Ignore.
CLASS            Ignore.
COMMENT          Ignore.


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CREATED          Ignore.
DAYLIGHT         Required if VTIMEZONE is implemented; otherwise
                 Ignore.


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                 ignore.
DESCRIPTION      Required.
DTSTAMP          Required.
DTSTART          Required.
DTEND            Required.
EXDATE           Ignore.
EXRULE           Ignore.
LAST-MODIFIED    Ignore.
RELATED-TO       Ignore.
RDATE            Ignore. If implemented, VTIMEZONE MUST also be
                 implemented.
RRULE            Ignore. The first instance occurs on the DTStart DTSTART
                 property.
SEQUENCE         Required.
STATUS           Ignore.
TRANSP           Required if FREEBUSY is implemented; otherwise ignore.
TZNAME           Required if VTIMEZONE is implemented; otherwise
                 ignore.
TZOFFSET         Required if VTIMEZONE is implemented; otherwise
                 ignore.
URL              Ignore.
UID              Required.
X-               Ignore.


5.2 Latency Issues

With a store-and-forward transport, it is possible for events to arrive
out of sequence. That is, you MAY receive a "CANCEL" method may be received prior to
receiving the associated "REQUEST" for the calendar component. This
section discusses a few of these scenarios.


5.2.1     Cancellation of an Unknown Calendar Component.

When a "CANCEL" method is received before the original "REQUEST" method
the calendar will be unable to correlate the "UID" property of the
cancellation with an existing calendar component. It is suggested that
messages that can not be correlated that also contain non-zero sequence
numbers be held and not discarded. Implementations MAY age them out if
no other messages arrive with the same "UID" property value and a lower
sequence number.


5.2.2     Unexpected Reply from an Unknown Delegate

When an "Attendee" delegates an item to another "Calendar User" CU they MUST send a
"REPLY" method to the "Organizer" using the "ATTENDEE" properties to
indicate the fact that the request was delegated and to
   whom the item was delegated. Hence whom. Hence, it is
possible for an "Organizer" to receive an "REPLY" from a "Calendar User" CU not listed
as one of the


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implementation but it is expected that the calendaring software will
either accept the reply or hold it until the related "REPLY" method is
received from the "delegator". "Delegator". If the version of the "REPLY" method is


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out of date the "Organizer" SHOULD treat the message as a "STATUS-REQUEST" "STATUS-
REQUEST" and update the delegate with the correct version.


5.3 Sequence Number

Under some conditions, a "CUA" MAY CUA may receive requests and replies with the
same "SEQUENCE" property value. The "DTSTAMP" property is utilized as a
tie-breaker when two items with the same "SEQUENCE" property value are
evaluated. Furthermore, the "SEQUENCE" property is SHOULD only incremented
when one or more of the following properties changes:

      .

DTSTART

      .
DTEND

      .
RDATE

      .
RRULE

      .
EXDATE

      .
EXRULE

      .
DUE (for VTODO components)

      .
and possibly LOCATION  (at the user's discretion)

6  Security Considerations

   This memo outlines

ITIP is an abstract transport protocol which will be bound to a real-time real-
time transport, a store-and-forward transport, and perhaps other
transports. The transport protocol will be responsible for providing
facilities for authentication and encryption using standard Internet
mechanisms that are mutually understood between the sender and receiver.


6.1 Security Threats


6.1.1     Spoofing the "Organizer"

In this memo, iTIP, the "Organizer" (or someone working on the "Organizer's"
behalf) is the only person authorized to make changes to an existing
"VEVENT", "VTODO", "VJOURNAL" calendar component and republish it or
redistribute the updates to the "Attendees". An iCalendar object that
maliciously changes or cancels an existing "VEVENT", "VTODO" or
"VJOURNAL" calendar component MAY may be constructed by someone other than
the "Organizer" and republished or sent to the "Attendees".


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6.1.2     Spoofing the "Attendee"

In this memo, iTIP, an "Attendee" of a "VEVENT", "VTODO", "VJOURNAL" "VEVENT" or "VTODO" calendar component (or
someone working on the "Attendee's" behalf) is the only person
authorized to update any parameter associated with their "ATTENDEE"
property and send it to the "Organizer". An iCalendar object that
maliciously changes the "ATTENDEE" parameters MAY may be constructed by
someone other than the real "Attendee" and sent to the "Organizer".




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6.1.3     Unauthorized Replacement of the Organizer

There will be circumstances when "Attendees" of an event or to-do
decide, using out-of-band mechanisms, that the "Organizer" must be
replaced. When the new "Organizer" sends out the updated "VEVENT" or
"VTODO" the "Attendee's" CUA will detect that the "Organizer" has been
changed, but it has no way of knowing whether or not the change was
mutually upon.


6.1.4     Eavesdropping

The iCalendar object is constructed with human-readable clear text. Any
information contained in an iCalendar object MAY may be read and/or changed
by unauthorized persons while the object is in transit.

6.1.4


6.1.5     Flooding a Calendar

Implementations MAY provide a means to automatically incorporate
"REQUEST" methods into a calendar. This presents the opportunity for a
calendar to be flooded with requests, which effectively block all the
calendar's free time.

6.1.5


6.1.6     Procedural Alarms

The "REQUEST" methods for "VEVENT" and "VTODO" calendar components MAY
contain "VALARM" calendar components. The "VALARM" calendar component MAY
may be of type PROCEDURE and MAY have an attachment
   containing some sort of containing an
executable program. Implementations that incorporate these types of
alarms are subject to any virus or malicious attack that MAY may occur as a
result of executing the attachment.


6.1.7     Unauthorized REFRESH Requests

It is possible for an "Organizer" to receive a "REFRESH" request from
someone who is not an "Attendee" of an event or to-do. Only "Attendee's"
of an event or to-do are authorized to receive replies to "REFRESH"
requests. Replying to such requests to anyone who is not an "Attendee"
may be a security problem.


6.2 Recommendations

For an application where the information is sensitive or critical and
the network is subject is subject to a high probability of attack, iTIP
transactions SHOULD be secured. This MAY may be accomplished using public
key technology, specifically Security Multiparts for MIME [RFC1847] in
the iTIP transport binding. This helps mitigate the threats of spoofing,
eavesdropping and malicious changes in transit.




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6.2.1     Use of [RFC1847] to secure iTIP transactions

iTIP transport bindings SHOULD provide a mechanism based on Security
Multiparts for MIME [RFC1847] to enable authentication of the sender's
identity, and privacy and integrity of the data being transmitted. This
allows the receiver of a signed iCalendar object to verify the identity
of the sender. This sender MAY may then be correlated


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property in the iCalendar object. If the correlation is made and the
sender is authorized to make the requested change or update then the
operation MAY may proceed. It also allows the message to be encrypted to
prevent unauthorized reading of the message contents in transit. iTIP
transport binding documents describe this process in detail.


6.2.2     Implementation Controls

The threat of unauthorized replacement of the "Organizer" SHOULD be
mitigated by a calendar system that uses this protocol by providing
controls or alerts that make "Calendar Users" aware of such "Organizer"
changes and allowing them to decide whether or not the request should be
honored.

The threat of flooding a calendar SHOULD be mitigated by a calendar
system that uses this protocol by providing controls that MAY may be used to
limit the acceptable sources for iTIP transactions, and perhaps the size
of messages and volume of traffic, by source.

The threat of malicious procedural alarms SHOULD be mitigated by a
calendar system that uses this protocol by providing controls that
   MAY may
be used to disallow procedural alarms in iTIP transactions and/or remove
all alarms from the object before delivery to the recipient.

The threat of unauthorized "REFRESH" requests SHOULD be mitigated by a
calendar system that uses this protocol by providing controls or alerts
that allow "Calendar User" to decide whether or not the request should
be honored.  An implementation MAY decide to maintain, for audit or
historical purposes,  "Calendar Users" who were part of an attendee list
and who were subsequently uninvited.  Similar controls or alerts should
be provided when a "REFRESH" request is received from these "Calendar
Users" as well.




7  Acknowledgments

A hearty thanks to the following individuals who have participated in
the drafting, review and discussion of this memo:

Anik Ganguly, Bruce Kahn, John Noerenberg, Leo Parker, John Rose, Vinod
Seraphin, Richard Shusterman, Derik Stenerson, John Sun, Kevin
Tsurutome.




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8  Bibliography

[ICAL] "Internet Calendaring and Scheduling Core Object Specification -
iCalendar", Internet-Draft, October 1997,
   ftp://ftp.ietf.org/internet-drafts/draft-ietf-calsch-ical-03.txt. ftp://ftp.ietf.org/internet-
drafts/draft-ietf-calsch-ical-03.txt.

[ICMS] "Internet Calendaring Model Specification", Internet-Draft,
October 1997, ftp://ftp.ietf.org/internet-drafts/draft-ietf-calsch-
   mod-01.txt. ftp://ftp.ietf.org/internet-drafts/draft-ietf-calsch-mod-
01.txt.

[ID-UTF8] "UTF-8, a transformation format of Unicode and ISO 10646",
Internet-Draft, July 1996, ftp://ftp.ietf.org/internet-drafts/draft-
yergeau-utf8-01.txt.

[IMIP] "iCalendar Message-Based Interoperability Protocol - iMIP",
Internet-Draft, October 1997, ftp://ftp.ietf.org/internet-
   drafts/draft-ietf-calsch-imip-01.txt. ftp://ftp.ietf.org/internet-drafts/draft-
ietf-calsch-imip-01.txt.

[ISO8601] "Data elements and interchange formats - information
interchange - Representation of dates and times", ISO 8601, 1996-06-
   15, 1996-06-15,
+1 (212) 642-4900 for ANSI Sales.

[VCAL] "vCalendar - The Electronic Calendaring and Scheduling Format -
Version 1.0", Versit Consortium, September 18, 1996,
http://www.imc.org/pdi/vcal-10.doc.


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[VCARD] "vCard - The Electronic Business Card Exchange Format - Version
2.1", Versit Consortium, September 18, 1996,
http://www.imc.org/pdi/vcard-21.doc.

[RFC821] Postel, "Simple Mail Transfer Protocol", RFC 821, organization
name, November 1996, http://ds.internic.net/rfc/rfc821.txt.

[RFC1983] "Internet Users' Glossary", RFC 1983, August 1996,
http://ds.internic.net/rfc/rfc1983.txt.

[RFC2119] "Key words for use in RFCs to Indicate Requirement Levels",
RFC 2119, March 1997, http://ds.internic.net/rfc/rfc2119.txt.

[RFC2045] N. Freed and N. Borenstein, "Multipurpose Internet Mail
Extensions - Part One - Format of Internet Message Bodies", RFC 2045,
Innosoft, First Virtual, November 1996,
http://ds.internic.net/rfc/rfc2045.txt.

[RFC2046] N. Freed and N. Borenstein, "Multipurpose Internet Mail
Extensions - Part Two - Media Types", RFC 2046, Innosoft, First Virtual,
November 1996, http://ds.internic.net/rfc/rfc2046.txt.

[UNICODE] The Unicode Consortium, "The Unicode Standard -Version 2.0",
Addison-Wesley Developers Press, July 1996. UTF-8 is described in
section A-2.

[US-ASCII] Coded Character Set--7-bit AmeriMAYStandard American Standard Code for
Information Interchange, ANSI X3.4-1986.


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9  Authors Addresses

The following address information is provided in a MIME-VCARD,
Electronic Business Card, format.

The authors of this draft are:


BEGIN:VCARD
VERSION:2.1
FN:Frank Dawson
ORG:Lotus Development Corporation
ADR;WORK;POSTAL;PARCEL:;;6544 Battleford Drive;Raleigh;NC;27613-
  3502;USA
TEL;WORK;MSG:+1-919-676-9515
TEL;WORK;FAX:+1-919-676-9564
EMAIL;INTERNET:Frank_Dawson@Lotus.com
URL:http://home.earthlink.net/~fdawson
END:VCARD

BEGIN:VCARD
VERSION:2.1
FN:Ross Hopson
ORG:On Technology, Inc.
ADR;WORK;POSTAL;PARCEL:Suite 1600;;434 Fayetteville St.
  Mall, Two Hannover Square;Raleigh;NC;27601
TEL;WORK;MSG:+1-919-890-4036


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TEL;WORK;FAX:+1-919-890-4100
EMAIL;INTERNET:rhopson@on.com
END:VCARD

BEGIN:VCARD
VERSION:2.1
FN:Steve Mansour
ORG:Netscape Communications Corporation
ADR;WORK;POSTAL;PARCEL:;;501 East Middlefield Road;Mountain
  View;CA;94043;USA
     TEL;WORK;MSG:+1-415-937-2378
     TEL;WORK;FAX:+1-415-428-4059
TEL;WORK;MSG:+1-650-937-2378
TEL;WORK;FAX:+1-650-937-2103
EMAIL;INTERNET:sman@netscape.com
END:VCARD

BEGIN:VCARD
VERSION:2.1
FN:Steve Silverberg
ORG:Microsoft Corporation
ADR;WORK;POSTAL;PARCEL:;;One Microsoft Way;
Redmond;WA;98052-6399;USA
TEL;WORK;MSG:+1-425-936-9277
TEL;WORK;FAX:+1-425-936-8019
EMAIL;INTERNET:stevesil@Microsoft.com
END:VCARD




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The iCalendar object is a result of the work of the Internet Engineering
Task Force Calendaring and scheduling Working Group. The chairman of
that working group is:


BEGIN:VCARD
FN:Anik Ganguly
ORG:Campbel Services, Inc.
ADR;WORK;POSTAL;PARCEL:10 Floor;;21700 Northwestern
  Highway;Southfield;MI;48075;USA
TEL;WORK;MSG:+1-248-559-5955
TEL;WORK;FAX:+1-248-559-5034
EMAIL;INTERNET:anik@ontime.com
END:VCARD


10 Full Copyright Statement

"Copyright (C) The Internet Society (date). All Rights Reserved.

This document and translations of it MAY may be copied and furnished to
others, and derivative works that comment on or otherwise explain it or
assist in its implmentation MAY 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 included
on all such copies and derivative works. However, this document itself MAY NOT
may not be modified in any way, such as by removing the copyright notice
or references to the Internet Society or other Internet organizations,
except as needed for the purpose of developing Internet standards in
which case the procedures for


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Standards process MUST must be followed, or as required to translate it into
languages other than English.

The limited permissions granted above are perpetual and will not may be
revoked by the Internet Society or its successors or assigns.

This document and the information contained herein is provided on an "AS
IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING TASK
FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING BUT NOT
LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION HEREIN WILL NOT
INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF MERCHANTABILITY OR
FITNESS FOR A PARTICULAR PURPOSE.














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