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Versions: 00 01 02 03 04

Network Working Group                                       E. York, Ed.
Internet-Draft                                             C. Daboo, Ed.
Intended status: Standards Track                              Apple Inc.
Expires: July 26, 2013                                  M. Douglass, Ed.
                                                                     RPI
                                                        January 22, 2013


          VPOLL: Consensus Scheduling Component for iCalendar
                          draft-york-vpoll-00

Abstract

   This specification introduces a new iCalendar component which allows
   for consensus scheduling, that is voting on a number of alternative
   meeting or task alternatives.

Status of this Memo

   This Internet-Draft is submitted in full conformance with the
   provisions of BCP 78 and BCP 79.

   Internet-Drafts are working documents of the Internet Engineering
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   This Internet-Draft will expire on July 26, 2013.

Copyright Notice

   Copyright (c) 2013 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal
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   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.



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Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  4
   2.  Conventions and Terms Used in This Document  . . . . . . . . .  4
   3.  Simple Consensus Scheduling  . . . . . . . . . . . . . . . . .  5
     3.1.  The VPOLL Component: An Overview . . . . . . . . . . . . .  5
     3.2.  The VPOLL Subcomponents: An Overview . . . . . . . . . . .  7
     3.3.  VPOLL responses  . . . . . . . . . . . . . . . . . . . . .  7
     3.4.  VPOLL updates  . . . . . . . . . . . . . . . . . . . . . .  8
     3.5.  VPOLL Completion . . . . . . . . . . . . . . . . . . . . .  9
   4.  iCalendar Extensions . . . . . . . . . . . . . . . . . . . . . 10
     4.1.  New Property Parameters  . . . . . . . . . . . . . . . . . 10
       4.1.1.  Public-Comment . . . . . . . . . . . . . . . . . . . . 10
       4.1.2.  Response . . . . . . . . . . . . . . . . . . . . . . . 10
       4.1.3.  Stay-Informed  . . . . . . . . . . . . . . . . . . . . 11
     4.2.  New Properties . . . . . . . . . . . . . . . . . . . . . . 11
       4.2.1.  Accept-Response  . . . . . . . . . . . . . . . . . . . 11
       4.2.2.  Poll-Item-Id . . . . . . . . . . . . . . . . . . . . . 12
       4.2.3.  Poll-Mode  . . . . . . . . . . . . . . . . . . . . . . 13
       4.2.4.  Poll-properties  . . . . . . . . . . . . . . . . . . . 14
       4.2.5.  Voter  . . . . . . . . . . . . . . . . . . . . . . . . 14
     4.3.  VPOLL Component  . . . . . . . . . . . . . . . . . . . . . 16
   5.  Poll Modes . . . . . . . . . . . . . . . . . . . . . . . . . . 18
     5.1.  POLL-MODE:BASIC  . . . . . . . . . . . . . . . . . . . . . 18
       5.1.1.  Property restrictions  . . . . . . . . . . . . . . . . 18
       5.1.2.  Outcome reporting  . . . . . . . . . . . . . . . . . . 19
   6.  iTip Extensions  . . . . . . . . . . . . . . . . . . . . . . . 19
     6.1.  Methods  . . . . . . . . . . . . . . . . . . . . . . . . . 19
     6.2.  Interoperability Models  . . . . . . . . . . . . . . . . . 20
       6.2.1.  Delegation . . . . . . . . . . . . . . . . . . . . . . 20
       6.2.2.  Acting on Behalf of Other Calendar Users . . . . . . . 20
       6.2.3.  Component Revisions  . . . . . . . . . . . . . . . . . 20
       6.2.4.  Message Sequencing . . . . . . . . . . . . . . . . . . 21
     6.3.  Application Protocol Elements  . . . . . . . . . . . . . . 21
       6.3.1.  Methods for VPOLL Calendar Components  . . . . . . . . 21
         6.3.1.1.  PUBLISH  . . . . . . . . . . . . . . . . . . . . . 22
         6.3.1.2.  REQUEST  . . . . . . . . . . . . . . . . . . . . . 24
           6.3.1.2.1.  Rescheduling a poll  . . . . . . . . . . . . . 27
           6.3.1.2.2.  Updating or Reconfirmation of an Poll  . . . . 27
           6.3.1.2.3.  Delegating a POll to Another CU  . . . . . . . 28
           6.3.1.2.4.  Changing the Organizer . . . . . . . . . . . . 28
           6.3.1.2.5.  Sending on Behalf of the Organizer . . . . . . 29
           6.3.1.2.6.  Forwarding to an Uninvited CU  . . . . . . . . 29
           6.3.1.2.7.  Updating Voter Status  . . . . . . . . . . . . 29
         6.3.1.3.  REPLY  . . . . . . . . . . . . . . . . . . . . . . 30
         6.3.1.4.  CANCEL . . . . . . . . . . . . . . . . . . . . . . 32
         6.3.1.5.  REFRESH  . . . . . . . . . . . . . . . . . . . . . 34
         6.3.1.6.  CONFIRM  . . . . . . . . . . . . . . . . . . . . . 35



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         6.3.1.7.  POLLSTATUS . . . . . . . . . . . . . . . . . . . . 37
   7.  CalDAV Extensions  . . . . . . . . . . . . . . . . . . . . . . 39
     7.1.  Calendar Collection Properties . . . . . . . . . . . . . . 39
       7.1.1.  CALDAV:vpoll-supported-component-set . . . . . . . . . 39
       7.1.2.  CALDAV:vpoll-max-items . . . . . . . . . . . . . . . . 40
       7.1.3.  CALDAV:vpoll-max-active  . . . . . . . . . . . . . . . 41
       7.1.4.  CALDAV:vpoll-max-voters  . . . . . . . . . . . . . . . 41
       7.1.5.  CalDAV:even-more-properties  . . . . . . . . . . . . . 42
     7.2.  Additional Preconditions for PUT, COPY, and MOVE . . . . . 43
     7.3.  CalDAV:calendar-query Report . . . . . . . . . . . . . . . 43
       7.3.1.  Example: Partial Retrieval of VPOLL  . . . . . . . . . 43
       7.3.2.  Example: Retrieval of Vpolls by sub-component Time
               Range  . . . . . . . . . . . . . . . . . . . . . . . . 46
     7.4.  CalDAV time ranges . . . . . . . . . . . . . . . . . . . . 47
     7.5.  freebusy reports . . . . . . . . . . . . . . . . . . . . . 48
   8.  Notes  . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49
   9.  Security Considerations  . . . . . . . . . . . . . . . . . . . 51
   10. IANA Considerations  . . . . . . . . . . . . . . . . . . . . . 51
     10.1. Parameter Registrations  . . . . . . . . . . . . . . . . . 51
     10.2. Property Registrations . . . . . . . . . . . . . . . . . . 51
     10.3. POLL-MODE Registration Template  . . . . . . . . . . . . . 52
     10.4. POLL-MODE Registrations  . . . . . . . . . . . . . . . . . 52
   11. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 52
   12. Normative References . . . . . . . . . . . . . . . . . . . . . 53
   Appendix A.  Open issues . . . . . . . . . . . . . . . . . . . . . 54
   Appendix B.  Change log  . . . . . . . . . . . . . . . . . . . . . 54
   Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 54
























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1.  Introduction

   The currently existing approach to agreeing on meeting times using
   iTip [RFC5546] and/or iMip [RFC6047] have some significant failings.
   There is no useful bargaining or suggestion mechanism in iTip, only
   the ability for a potential attendee to accept or refuse or to
   counter with a time of their own choosing.

   Part of the problem is that for many potential attendees, their
   freebusy is not an accurate representation of their avalability.  In
   fact, when trying to schedule conference calls across different
   organizations, attendees may not be allowed to provide freebusy
   information or availability as this may reveal something of the
   organizations internal activities.

   A number of studies have shown that large amounts of time are spent
   trying to come to an agreement - up to and beyond 20 working hours
   per meeting. many organizers fall back on other approachessuch as
   phone calls and email to determine a suitable time.

   Online services have appeared as a result and these allow
   participants to vote on a number of alternatives without revealing or
   using freebusy or availability.  When agreement is reached a
   conventional scheduling message may be sent to the attendees.  This
   approach appears to reach consensus fairly rapidly.  Peer pressure
   may have some bearing on this as all voters are able to see the
   current state of the voting and may adjust their own meeting
   schedules to make themselves available for a popular choice.

   The component and properties defined in this specification provide a
   standardized structure to this process and allow calendar clients and
   servers and these web based services to interact.

   These structures also have uses beyond the relatively simple needs of
   most meeting organizers.  The process of coming to consensus can also
   be viewed as a bidding process.


2.  Conventions and Terms Used in This Document

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
   "OPTIONAL" in this document are to be interpreted as described in
   [RFC2119].

   Additionally we will use the following terms:





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   Consensus Scheduling:  The process whereby we come to some agreement
      on meeting or task alternatives and then book that meeting or
      task.

   Active Vpoll:  A vpoll may have a DTSTART, DTEND and DURATION which
      may define the start and end of the active voting period.

   Voter:  A participant who votes on th ealternatives.  A voter need
      not be an attendee of any of the alternatives presented.


3.  Simple Consensus Scheduling

   This specification defines components and properties which can be
   used for simple consensus scheduling but also have the generality to
   handle more complex cases.  To provide an easy (and for many -
   sufficient) introduction to consensus scheduling and VPOLL we will
   outline the flow of information for the simple case of voting on a
   number of meeting alternatives which differ only in time.  In
   addition the voters will all be potential attendees.

   This specification not only defines data structures but adds a new
   iTip method used when consensus has been reached. we will show how a
   VPOLL object is used to inform voters of the state of a simple vote
   on some alternatives.

3.1.  The VPOLL Component: An Overview

   The VPOLL component acts as a wrapper for a number of alternatives to
   be voted on together with some properties used to maintain the state
   of the voting.  For our simple example the following VPOLL properties
   and sub-components are either required or appropriate:

   DTSTAMP:  The usual [RFC5545] property.

   SEQUENCE:  The usual [RFC5545] property.  See below for SEQUENCE
      behavior.

   UID:  The usual [RFC5545] property.

   ORGANIZER:  The usual [RFC5545] property.  In general this need not
      be an organizer of any of the alternatives.  In this simple
      outline we assume it is the same.

   SUMMARY:  The usual [RFC5545] property.  This optional but
      recommended property provides the a short title to the poll.





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   DESCRIPTION:  The usual [RFC5545] property.  This optional property
      provides more details.

   DTEND:  The usual [RFC5545] property.  This optional property
      provides a poll closing time and date after which the VPOLL is no
      longer active.

   POLL-MODE:  A new property which defines how the votes are used to
      obtain a result.  For our use case it will take the value "BASIC"
      meaning one event will be chosen from the alternatives.

   POLL-PROPERTIES:  A new property which defines which icalendar
      properties are being voted on.  For our use case it will take the
      value "DTSTART, LOCATION" meaning only those properties are
      significant for voting.  Other properties in the events may differ
      but are not considered significant for the voting process.

   VOTER:  A new property.  There is one of these for each voter and it
      is similar to the [RFC5545] ATTENDEE property.  In the VPOLL
      component it shows who takes part in the voting.

   VEVENT:  In our simple use case there will be multiple VEVENT sub-
      components defining the alternatives.  Each will have adifferent
      date and or time for the meeting.

   Putting that together we can construct an example VPOLL with 3 voters
   and 3 alternative meetings:

          BEGIN:VCALENDAR
          VERSION:2.0
          PRODID:-//Example//Example
          METHOD:REQUEST
          BEGIN:VPOLL
          POLL-MODE:BASIC
          POLL-PROPERTIES:DTSTART,LOCATION
          ORGANIZER:mailto:mike@example.com
          UID:sched01-1234567890
          DTSTAMP:20120101T000000Z
          SUMMARY:What to do this week
          DTEND:20120101T000000Z
          VOTER:mailto:cyrus@exmaple.com
          VOTER:mailto:eric@example.com
          VEVENT.......(with a poll-item-id=1)
          VEVENT.......(with a poll-item-id=2)
          VEVENT.......(with a poll-item-id=3)
          END:VPOLL
          END:VCALENDAR




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   As can be seen in the example above, there is an iTip METHOD property
   with the value REQUEST.  The VPOLL object will be distributed to all
   the voters, either through iMipor through some VPOLL enabled service.

3.2.  The VPOLL Subcomponents: An Overview

   Within the VPOLL component we have the alternatives to vote on.  In
   many respects these are standard [RFC5545] components.  For our
   simple use case they are all VEVENT components.  In addition to the
   usual [RFC5545] properties some extra properties are used for a
   VPOLL.

   POLL-ITEM-ID:  This provides a unique reference to the sub-component
      within the VPOLL.  It's value SHOULD be a small integer.

   VOTER:  The VOTER property within a VPOLL sub-component specifies the
      state of the vote for that voter.  The RESPONSE parameter supplies
      the current vote in the range 0 to 100.  For many purposes this is
      too fine grained and recommended values are defined for voting
      preferences of "NO", "MAYBE" and "YES" with an additional "YES but
      not the preferred outcome".  These properties will be added to the
      sub-components as responses appear.

3.3.  VPOLL responses

   Upon receipt of a VPOLL REQUEST the voter will reply with a VPOLL
   component containing their vote.  In our simple case it will have the
   following properties:

   DTSTAMP:  The usual [RFC5545] property.

   SEQUENCE:  The usual [RFC5545] property.  See below for SEQUENCE
      behavior.

   UID:  Same as the request.

   ORGANIZER:  Same as the request.

   SUMMARY:  Same as the request.

   VOTER:  One only - the voter replying.

   POLL-ITEM-ID:  One per item being voted on.  There does not need to
      be one for each sub-component but each REPLY will set the voting
      state for every sub-component.

   Note that a voter can send a number of REPLYs for each REQUEST sent
   by the organizer.  Each REPLY completely replaces the voting record



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   for that voter for all components being voted on.  In our example, if
   Eric respondes and votre for items 1 and 2 and then responds again
   with a vote for only item 3 the final outcome is one vote on item 3.

   Putting this together we can construct an example REPLY VPOLL from
   Cyrus:

          BEGIN:VCALENDAR
          VERSION:2.0
          PRODID:-//Example//Example
          METHOD: REPLY
          BEGIN:VPOLL
          ORGANIZER:mailto:douglm@example.com
          VOTER:mailto:cyrus@example.com
          UID:sched01-1234567890
          DTSTAMP:20120101T010000Z
          SUMMARY:What to do this week
          POLL-ITEM-ID;RESPONSE=50;PUBLIC-COMMENT=Work on iTIP:1
          POLL-ITEM-ID;RESPONSE=100;COMMENT=Work on WebDAV:2
          POLL-ITEM-ID;RESPONSE=0:3
          END:VPOLL
          END:VCALENDAR

3.4.  VPOLL updates

   When the organizer receives a response from one or more voters the
   current state of the poll is sent to all voters.  The new iTip method
   POLLSTATUS is used.  The VPOLL can contain a reduced set of
   properties but MUST contain DTSTAMP, SEQUENCE (if not 0), UID,
   ORGANIZER and VOTER.

   In addition, for our use case, it will contain skeleton VEVENT sub-
   components with the POLL-ITEM-ID and VOTER properties.  Clients
   receiving this poll status SHOULD merge it in to their own copy to
   give the full current status

   An example:














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          BEGIN:VCALENDAR
          VERSION:2.0
          PRODID:-//Example//Example
          METHOD: POLLSTATUS
          BEGIN:VPOLL
          ORGANIZER:mailto:douglm@example.com
          VOTER:mailto:cyrus@example.com
          VOTER:mailto:eric@example.com
          UID:sched01-1234567890
          DTSTAMP:20120101T020000Z
          SEQUENCE:0
          SUMMARY:What to do this week
          BEGIN:VEVENT
          POLL-ITEM-ID: 1
          VOTER;RESPONSE=50;COMMENT=Work on iTIP:
           mailto:cyrus@exmaple.com
          VOTER;RESPONSE=100:mailto:eric@example.com
          END:VEVENT
          BEGIN:VEVENT
          POLL-ITEM-ID: 2
          VOTER;RESPONSE=100;COMMENT=Work on WebDAV:
           mailto:cyrus@exmaple.com
          VOTER;RESPONSE=100:mailto:eric@example.com
          END:VEVENT
          BEGIN:VEVENT
          POLL-ITEM-ID: 3
          VOTER;RESPONSE=0:mailto:cyrus@example.com
          VOTER;RESPONSE=0:mailto:eric@example.com
          END:VEVENT
          END:VPOLL
          END:VCALENDAR

3.5.  VPOLL Completion

   After a number of REPLY messages have been received the poll will be
   considered complete.  If there is a DTEND on the poll the system may
   automatically close the poll, or the organizer may, at any time,
   consider the poll complete.

   The poll is completed by sending a final iTip message with the new
   CONFIRM method.  In this case the VPOLL component contains ...

   The VPOLL conformation example:








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          BEGIN:VCALENDAR
          VERSION:2.0
          PRODID:-//Example//Example
          METHOD: CONFIRM
          BEGIN:VPOLL
          ORGANIZER:mailto:douglm@example.com
          UID:sched01-1234567890
          DTSTAMP:20120101T030000Z
          COMPLETED:20120101T030000Z
          SEQUENCE:0
          SUMMARY:What to do this week
          BEGIN:VEVENT
          UID:123
          ......
          END:VEVENT


4.  iCalendar Extensions

4.1.  New Property Parameters

4.1.1.  Public-Comment

   Parameter name:  PUBLIC-COMMENT

   Purpose:  To allow voters to provide a public comment in their
      reponse.

   Format Definition:

      This parameter is defined by the following notation:

      public-comment-param = "PUBLIC-COMMENT=" DQUOTE text DQUOTE

   Description:  This parameter can be specified on the POLL-ITEM-ID
      property to allow a voter to add some commentary visible to all
      voters.

4.1.2.  Response

   Parameter name:  RESPONSE

   Purpose:  To specify a response vote.

   Format Definition:






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      This parameter is defined by the following notation:

       responseparam = "RESPONSE=" integer
             ; integer value 0..100

   Description:  This parameter can be specified on the POLL-ITEM-ID
      property to provide the value of the voters response.  This
      parameter allows for fine grained responses which are appropriate
      to some applications.  For the case of individuals voting for a
      choice of events, client applications SHOULD conform to the
      following convention:

      *  0 - 39 A "NO vote".

      *  40 - 79 A "MAYBE" vote

      *  80 - 89 A "YES - but not preferred vote"

      *  90-100 A "YES" vote.

      Clients MUST preserve the responseparam value when there is no
      change from the user even if they have a UI with fixed states
      (e.g. yes/no/maybe).

4.1.3.  Stay-Informed

   Parameter name:  STAY-INFORMED

   Purpose:  To specify the voter also wants to be added as an ATTENDEE
      when the poll is confirmed.

   Format Definition:

      This parameter is defined by the following notation:

       stayinformedparam = "STAY-INFORMED" "=" boolean

   Description:  This parameter MAY be specified on VOTER and, if the
      value is TRUE, indicates the voter wishes to be added to the final
      choice as a non participant.

4.2.  New Properties

4.2.1.  Accept-Response







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   Property name:  ACCEPT-RESPONSE

   Purpose:  This property is used in VPOLL to indicate the types of
      component that may be supplied in a response.

   Property Parameters:  Non-standard or iana parameters can be
      specified on this property.

   Conformance:  This property MAY be specified in a VPOLL component.

   Description:  When used in a VPOLL this property indicates what
      allowable component types may be returned in a reply.  Typically
      this would allow a voter to respond with the freebusy or
      availability rather than choosing one of the presented
      alternatives

      If this property is not present voters are only allowed to respond
      with the same component type as in the request.

   Format Definition:

      This property is defined by the following notation:

     acceptresponse = "ACCEPT-RESPONSE" "="
                          acceptresponseparams ":"
                          iana-token ("," iana-token) CRLF

     acceptresponseparams = *(";" other-param)

4.2.2.  Poll-Item-Id

   Property name:  POLL-ITEM-ID

   Purpose:  This property is used in VPOLL to indicate recipients of
      the poll and in VPOLL sub-components to give the voters response.

   Value type:  The value type for this property is param-value.

   Property Parameters:  Non-standard, response, public-comment or
      stayinformed parameters can be specified on this property.

   Conformance:  This property MAY be specified in a VPOLL component or
      its sub-components.

   Description:  In a METHOD:REQUEST each child component MUST have a
      POLL-ITEM-ID property.  Each set of components with the same POLL-
      ITEM-ID value represents one overall set of items to be voted on.




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      POLL-ITEM-ID SHOULD be a unique ID for each component or set of
      components.  If it remains the same between REQUESTs then the
      previous response for that component MAY be re-used.  To force a
      re-vote on a component due to a significant change, the
      POLL-ITEM-ID MUST change.

      In a METHOD:REPLY there is a single VPOLL component which MUST
      have: either one or more POLL-ITEM-ID properties with a RESPONSE
      param matching that from a REQUEST or a VFREEBUSY or VAVAILABILITY
      child component showing overall busy/available time.

   Format Definition:

      This property is defined by the following notation:

             pollitemid = "POLL-ITEM-ID" pollitemdparams ":"
                        param-value CRLF

             pollitemidparams = *(
                         (";" responseparam) /
                         (";" stayinformedparam) /
                         (";" public-comment-param) /
                         (";" other-param)
                  )


4.2.3.  Poll-Mode

   Property name:  POLL-MODE

   Purpose:  This property is used in VPOLL to indicate what voting mode
      is to be applied.

   Property Parameters:  Non-standard or iana parameters can be
      specified on this property.

   Conformance:  This property MAY be specified in a VPOLL component or
      its sub-components.

   Description:  The poll mode defines how the votes are applied to
      obtain a result.  BASIC mode, the default, means that the voters
      are selecting one component (or group of components) with a given
      POLL=ITEM-ID.

      Other polling modes may be defined in updates to this
      specification.  These may allow for such modes as ranking or task
      assignment.




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   Format Definition:

      This property is defined by the following notation:

             pollmode = "POLL-MODE" pollmodeparams ":"
                 ("BASIC" / iana-token / other-token) CRLF

             pollmodeparams = *(";" other-param)


   Note  If the client does not understand the poll mode in use it
      should use the LINK property to get the web-based view of the
      poll.

4.2.4.  Poll-properties

   Property name:  POLL-PROPERTIES

   Purpose:  This property is used in VPOLL to define which icalendar
      properties are being voted on.

   Property Parameters:  Non-standard or iana parameters can be
      specified on this property.

   Conformance:  This property MAY be specified in a VPOLL component.

   Description:  This property defines which icalendar properties are
      significant in the voting process.  It may not be clear to voters
      which properties are varying in a significant manner.  Clients may
      use this property to highlight those listed properties.

   Format Definition:

      This property is defined by the following notation:

             pollproperties = "POLL-PROPERTIES" pollpropparams ":"
                 text *("," text) CRLF

             pollpropparams = *(";" other-param)


4.2.5.  Voter

   Property name:  VOTER







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   Purpose:  This property is used in VPOLL to indicate recipients of
      the poll and in VPOLL sub-components to give the voters response.

   Value type:  The value type for this property is cal-address.

   Property Parameters:  Non-standard, cutype, member, role, rsvp,
      delto, delfrom, sentby, cn, dir, lang, response or stayinformed
      parameters can be specified on this property.

   Conformance:  This property MAY be specified in a VPOLL component or
      its sub-components.

   Description:  When used in a VPOLL this property indicates who the
      poll is sent to.  When used in sub-components of VPOLL this
      property indicate the response of each voter as known at that
      time.

      When the Organizer sends a full update (METHOD:REQUEST), then
      VOTER properties MUST be included in the child components for any
      voters that have responded.

   Format Definition:

      This property is defined by the following notation:

       voter = "VOTER" voterparams ":" cal-address CRLF

       voterparam   = *(
                       ;
                       ; The following are OPTIONAL,
                       ; but MUST NOT occur more than once.
                       ;
                       (";" cutypeparam) / (";" memberparam) /
                       (";" roleparam) /
                       (";" rsvpparam) / (";" deltoparam) /
                       (";" delfromparam) / (";" sentbyparam) /
                       (";" cnparam) / (";" dirparam) /
                       (";" languageparam) /
                       (";" responseparam) /
                       (";" stayinformedparam) /
                       ;
                       ; The following is OPTIONAL,
                       ; and MAY occur more than once.
                       ;
                       (";" other-param)
                       ;
                 )




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   Note  RSVP=TRUE MAY used by the organizer to force the voter to reset
      their state and re-vote.

4.3.  VPOLL Component

   Component name:  VPOLL

   Purpose:  This component provides a mechanism by which voters can
      vote on provided choices.

   Format Definition:








































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      This property is defined by the following notation:

     pollc    = "BEGIN" ":" "VPOLL" CRLF
                  pollprop
                  *eventc *todoc *journalc *freebusyc
                  *availabilityc *alarmc *iana-comp *x-comp
                  "END" ":" "VPOLL" CRLF

     pollprop = *(
                ;
                ; The following are REQUIRED,
                ; but MUST NOT occur more than once.
                ;
                dtstamp / uid / organizer /
                ;
                ; The following are OPTIONAL,
                ; but MUST NOT occur more than once.
                ;
                acceptresponse / class / created / completed /
                description / dtstart / last-mod / pollmode /
                pollproperties / priority / seq / status /
                summary / url /
                ;
                ; Either 'dtend' or 'duration' MAY appear in
                ; a 'pollprop', but 'dtend' and 'duration'
                ; MUST NOT occur in the same 'pollprop'.
                ; 'duration' MUST only occur when 'dtstart'
                ; is present
                ;
                dtend / duration /
                ;
                ; The following are OPTIONAL,
                ; and MAY occur more than once.
                ;
                attach / categories / comment /
                contact / link / pollitemid / pollwinner /
                rstatus / related /
                resources / voter / x-prop / iana-prop
                ;
                )

   Description:  This component provides a mechanism by which voters can
      vote on provided choices.  The outcome depends upon the POLL-MODE
      in effect.







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      VOTER in VPOLL requests refers to each person who will be voting -
      RSVP=TRUE is used by the organizer to force the voter to reset
      their state and re-vote

      If specified, the "DTSTART" property defines the start or opening
      of the poll active period.  If absent the poll is presumed to have
      started when created.

      If "DTSTART"is present "DURATION" MAY be specified and indicates
      the duration, and hence the ending, of the poll.  The value of the
      property MUST be a positive duration.

      "DTEND" MAY be specified with or without "DTSTART" and indicates
      the ending of the poll.  If DTEND is specified it MUST be later
      than the DTSTART or CREATED property.

      If one or more VALARM components are included in the VPOLL they
      are not components to be voted on and MUST NOT contain a POLL-
      ITEM-ID property.  VALARM sub-components may be used to provide
      warnings to the user when polls are due to start or end.

      Need some text to describe what relative alarms are relative to.


5.  Poll Modes

   The VPOLL component is intended to allow for various forms of
   polling.  The particular form in efffect is indicated by the POLL-
   MODE property.

   To define new poll modes create an RFC defining the new mode and
   provide the registration information as specified in Section 10.3.

5.1.  POLL-MODE:BASIC

   BASIC poll mode is the form of voting in which one possible outcome
   is chosen from a set of possibilities.  Usually this will be
   represented as a number of possible event objects one of which will
   be selected.

5.1.1.  Property restrictions

   This poll mode places no special restrictions on properties beyond
   those specified in the description of the generic VPOLL component.







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5.1.2.  Outcome reporting

   For a METHOD:CONFIRM there must be a single sub-component in the
   VPOLL object which represents the succesful candidate from the
   supplied choices.

   Winning Non-scheduled VEVENTs or VTODOs MUST be assigned an ORGANIZER
   property and a list of non-participating ATTENDEEs.


6.  iTip Extensions

   This specification introduces a number of extensions to [RFC5546].
   In group scheduling the parties involved are organizer and attendees.
   In VPOLL the parties are organizer and voters.

   For many of the iTip processing rules the voters take the place of
   attendees.

6.1.  Methods

   There are some extensions to the behavior of iTip methods for a VPOLL
   object and two new methods are defined.

   +----------------+--------------------------------------------------+
   | Method         | Description                                      |
   +----------------+--------------------------------------------------+
   | PUBLISH        | No changes (yet)                                 |
   |                |                                                  |
   | REQUEST        | Each child component MUST have a POLL-ITEM-ID    |
   |                | property.  Each set of components with the same  |
   |                | POLL-ITEM-ID value represents one overall set of |
   |                | items to be voted on.                            |
   |                |                                                  |
   | REPLY          | There MUST be a single VPOLL component which     |
   |                | MUST have: either one or more POLL-ITEM-ID       |
   |                | properties with a RESPONSE param matching that   |
   |                | from a REQUEST or a VFREEBUSY or VAVAILABILITY   |
   |                | child component showing overall busy/available   |
   |                | time.  The VPOLL MUST have one VOTER only.       |
   |                |                                                  |
   | ADD            | Not supported for VPOLL.                         |
   |                |                                                  |
   | CANCEL         | There MUST be a single VPOLL component with UID  |
   |                | matching that of the poll being cancelled.       |
   |                |                                                  |





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   | REFRESH        | The organizer returns a METHOD:REQUEST with the  |
   |                | current full state, or a METHOD:CANCEL or a      |
   |                | METHOD:CONFIRM or an error if no matching poll   |
   |                | is found.                                        |
   |                |                                                  |
   | COUNTER        | Not supported for VPOLL.                         |
   |                |                                                  |
   | DECLINECOUNTER | Not supported for VPOLL.                         |
   |                |                                                  |
   | POLLSTATUS     | Used to send the current state of the poll to    |
   |                | all voters.  The VPOLL can contain a reduced set |
   |                | of properties but MUST contain DTSTAMP, SEQUENCE |
   |                | (if not 0), UID, ORGANIZER and VOTER.            |
   |                |                                                  |
   | CONFIRM        | The VPOLL MUST have all the components from the  |
   |                | chosen POLL-ITEM-ID set.                         |
   +----------------+--------------------------------------------------+

   The following table shows the above methods broken down by who can
   send them with VPOLL components.

      +------------+------------------------------------------------+
      | Originator | Methods                                        |
      +------------+------------------------------------------------+
      | Organizer  | PUBLISH, REQUEST, POLLSTATUS                   |
      |            |                                                |
      | Voter      | REPLY, REFRESH, REQUEST (only when delegating) |
      +------------+------------------------------------------------+

6.2.  Interoperability Models

   Most of the standard iTip specification applies with respect to
   organizer and voters.

6.2.1.  Delegation

   TBD

6.2.2.  Acting on Behalf of Other Calendar Users

   TBD

6.2.3.  Component Revisions

   Need to talk about what a change in SEQUENCE means
   Sequence change forces a revote.
   New voter - no sequence change
   Add another poll set or change poll item ids or any change to a child



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   component - bump sequence

6.2.4.  Message Sequencing

   TBD

6.3.  Application Protocol Elements

6.3.1.  Methods for VPOLL Calendar Components

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

   The presence column uses the following values to assert whether a
   property is required or optional, and the number of times it may
   appear in the iCalendar object.

   +----------------+--------------------------------------------------+
   | Presence Value | Description                                      |
   +----------------+--------------------------------------------------+
   | 1              | One instance MUST be present.                    |
   | 1+             | At least one instance MUST be present.           |
   | 0              | Instances of this property MUST NOT be present.  |
   | 0+             | Multiple instances MAY be present.               |
   | 0 or 1         | Up to 1 instance of this property MAY be         |
   |                | present.                                         |
   +----------------+--------------------------------------------------+

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



















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   +------------+------------------------------------------------------+
   | Method     | Description                                          |
   +------------+------------------------------------------------------+
   | PUBLISH    | Post notification of an poll.  Used primarily as a   |
   |            | method of advertising the existence of a poll.       |
   |            |                                                      |
   | REQUEST    | Make a request for a poll.  This is an explicit      |
   |            | invitation to one or more voters.  Poll requests are |
   |            | also used to update or change an existing poll.      |
   |            | Clients that cannot handle REQUEST MAY degrade the   |
   |            | poll to view it as a PUBLISH.                        |
   |            |                                                      |
   | REPLY      | Reply to a poll request.  Voters may set their       |
   |            | RESPONSE parameter to supply the current vote in the |
   |            | range 0 to 100.                                      |
   |            |                                                      |
   | CANCEL     | Cancel a poll.                                       |
   |            |                                                      |
   | REFRESH    | A request is sent to an Organizer by a Voter asking  |
   |            | for the latest version of a poll to be resent to the |
   |            | requester.                                           |
   |            |                                                      |
   | POLLSTATUS | Used to send the current state of the poll to all    |
   |            | voters.  The VPOLL can contain a reduced set of      |
   |            | properties but MUST contain DTSTAMP, SEQUENCE (if    |
   |            | not 0), UID, ORGANIZER and VOTER.                    |
   |            |                                                      |
   | CONFIRM    | Used to signal that the poll has been closed with a  |
   |            | choice made.                                         |
   +------------+------------------------------------------------------+

6.3.1.1.  PUBLISH

   The "PUBLISH" method in a "VPOLL" calendar component is an
   unsolicited posting of an iCalendar object.  Any CU may add published
   components to their calendar.  The "Organizer" MUST be present in a
   published iCalendar component.  "Voters" MUST NOT be present.  Its
   expected usage is for encapsulating an arbitrary poll as an iCalendar
   object.  The "Organizer" may subsequently update (with another
   "PUBLISH" method) or cancel (with a "CANCEL" method) a previously
   published "VPOLL" calendar component.

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

              +---------------------------------------------+
              | Constraints for a METHOD:PUBLISH of a VPOLL |
              +---------------------------------------------+



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   +--------------------+----------+-----------------------------------+
   | Component/Property | Presence | Comment                           |
   +--------------------+----------+-----------------------------------+
   | METHOD             | 1        | MUST equal PUBLISH.               |
   |                    |          |                                   |
   | VPOLL              | 1+       |                                   |
   |   DTSTAMP          | 1        |                                   |
   |   DTSTART          | 1        |                                   |
   |   ORGANIZER        | 1        |                                   |
   |   SUMMARY          | 1        | Can be null.                      |
   |   UID              | 1        |                                   |
   |   SEQUENCE         | 0 or 1   | MUST be present if value is       |
   |                    |          | greater than 0; MAY be present if |
   |                    |          | 0.                                |
   |   ACCEPT-RESPONSE  | 0 or 1   |                                   |
   |   ATTACH           | 0+       |                                   |
   |   CATEGORIES       | 0+       |                                   |
   |   CLASS            | 0 or 1   |                                   |
   |   COMMENT          | 0+       |                                   |
   |   COMPLETED        | 0 or 1   |                                   |
   |   CONTACT          | 0 or 1   |                                   |
   |   CREATED          | 0 or 1   |                                   |
   |   DESCRIPTION      | 0 or 1   | Can be null.                      |
   |   DTEND            | 0 or 1   | If present, DURATION MUST NOT be  |
   |                    |          | present.                          |
   |   DURATION         | 0 or 1   | If present, DTEND MUST NOT be     |
   |                    |          | present.                          |
   |   LAST-MODIFIED    | 0 or 1   |                                   |
   |   POLL-ITEM-ID     | 0        |                                   |
   |   POLL-MODE        | 0 or 1   |                                   |
   |   POLL-PROPERTIES  | 0 or 1   |                                   |
   |   PRIORITY         | 0 or 1   |                                   |
   |   RELATED-TO       | 0+       |                                   |
   |   RESOURCES        | 0+       |                                   |
   |   STATUS           | 0 or 1   | MAY be one of                     |
   |                    |          | TENTATIVE/CONFIRMED/CANCELLED.    |
   |   URL              | 0 or 1   |                                   |
   |   IANA-PROPERTY    | 0+       |                                   |
   |   X-PROPERTY       | 0+       |                                   |
   |   VOTER            | 0        |                                   |
   |   REQUEST-STATUS   | 0        |                                   |
   |                    |          |                                   |
   |   VALARM           | 0+       |                                   |
   |                    |          |                                   |







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   | VEVENT             | 0+       | Depending upon the poll mode in   |
   |                    |          | effect there MAY be candidate     |
   |                    |          | components included in the poll   |
   |                    |          | component.  If voting has already |
   |                    |          | taken place, these components     |
   |                    |          | MUST include the VOTER property   |
   |                    |          | to indicate each voters current   |
   |                    |          | response.                         |
   |                    |          |                                   |
   | VFREEBUSY          | 0        |                                   |
   |                    |          |                                   |
   | VJOURNAL           | 0+       | Depending upon the poll mode in   |
   |                    |          | effect there MAY be candidate     |
   |                    |          | components included in the poll   |
   |                    |          | component.  If voting has already |
   |                    |          | taken place, these components     |
   |                    |          | MUST include the VOTER property   |
   |                    |          | to indicate each voters current   |
   |                    |          | response.                         |
   |                    |          |                                   |
   | VTODO              | 0+       | Depending upon the poll mode in   |
   |                    |          | effect there MAY be candidate     |
   |                    |          | components included in the poll   |
   |                    |          | component.  If voting has already |
   |                    |          | taken place, these components     |
   |                    |          | MUST include the VOTER property   |
   |                    |          | to indicate each voters current   |
   |                    |          | response.                         |
   |                    |          |                                   |
   | VTIMEZONE          | 0+       | MUST be present if any date/time  |
   |                    |          | refers to a timezone.             |
   |                    |          |                                   |
   | IANA-COMPONENT     | 0+       |                                   |
   | X-COMPONENT        | 0+       |                                   |
   +--------------------+----------+-----------------------------------+

6.3.1.2.  REQUEST

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

   o  Invite "Voters" to respond to the poll.

   o  Change the items being voted upon.

   o  Response to a "REFRESH" request.





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   o  Update the details of an existing vpoll.

   o  Update the status of "Voters".

   o  Forward a "VPOLL" to another uninvited CU.

   o  For an existing "VPOLL" calendar component, delegate the role of
      "Voter" to another CU.

   o  For an existing "VPOLL" calendar component, change the role of
      "Organizer" to another CU.

   The "Organizer" originates the "REQUEST".  The recipients of the
   "REQUEST" method are the CUs voting in th epoll, the "Voters".
   "Voters" use the "REPLY" method to convey votesto the "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 "VPOLL" calendar component.  If the "UID"
   property value is found on the recipient's calendar, then the
   "REQUEST" is for an update, or a reconfirmation of the "VPOLL"
   calendar component.

   For the "REQUEST" method only a single iCalendar object is permitted.

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

              +---------------------------------------------+
              | Constraints for a METHOD:REQUEST of a VPOLL |
              +---------------------------------------------+

   +--------------------+----------+-----------------------------------+
   | Component/Property | Presence | Comment                           |
   +--------------------+----------+-----------------------------------+
   | METHOD             | 1        | MUST be REQUEST.                  |
   |                    |          |                                   |
   | VPOLL              | 1        |                                   |
   |   VOTER            | 1+       |                                   |
   |   DTSTAMP          | 1        |                                   |
   |   DTSTART          | 1        |                                   |
   |   ORGANIZER        | 1        |                                   |
   |   SEQUENCE         | 0 or 1   | MUST be present if value is       |
   |                    |          | greater than 0; MAY be present if |
   |                    |          | 0.                                |
   |   SUMMARY          | 1        | Can be null.                      |
   |   UID              | 1        |                                   |



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   |   ACCEPT-RESPONSE  | 0 or 1   |                                   |
   |   ATTACH           | 0+       |                                   |
   |   CATEGORIES       | 0+       |                                   |
   |   CLASS            | 0 or 1   |                                   |
   |   COMMENT          | 0+       |                                   |
   |   COMPLETED        | 0 or 1   |                                   |
   |   CONTACT          | 0+       |                                   |
   |   CREATED          | 0 or 1   |                                   |
   |   DESCRIPTION      | 0 or 1   | Can be null.                      |
   |   DTEND            | 0 or 1   | If present, DURATION MUST NOT be  |
   |                    |          | present.                          |
   |   DURATION         | 0 or 1   | If present, DTEND MUST NOT be     |
   |                    |          | present.                          |
   |   GEO              | 0 or 1   |                                   |
   |   LAST-MODIFIED    | 0 or 1   |                                   |
   |   LOCATION         | 0 or 1   |                                   |
   |   POLL-ITEM-ID     | 0        |                                   |
   |   POLL-MODE        | 0 or 1   |                                   |
   |   POLL-PROPERTIES  | 0 or 1   |                                   |
   |   PRIORITY         | 0 or 1   |                                   |
   |   RELATED-TO       | 0+       |                                   |
   |   REQUEST-STATUS   | 0        |                                   |
   |   RESOURCES        | 0+       |                                   |
   |   STATUS           | 0 or 1   | MAY be one of                     |
   |                    |          | TENTATIVE/CONFIRMED.              |
   |   TRANSP           | 0 or 1   |                                   |
   |   URL              | 0 or 1   |                                   |
   |   IANA-PROPERTY    | 0+       |                                   |
   |   X-PROPERTY       | 0+       |                                   |
   |                    |          |                                   |
   |   VALARM           | 0+       |                                   |
   |                    |          |                                   |
   | VTIMEZONE          | 0+       | MUST be present if any date/time  |
   |                    |          | refers to a timezone.             |
   |                    |          |                                   |
   | IANA-COMPONENT     | 0+       |                                   |
   | X-COMPONENT        | 0+       |                                   |
   |                    |          |                                   |
   | VEVENT             | 0+       | Depending upon the poll mode in   |
   |                    |          | effect there MAY be candidate     |
   |                    |          | components included in the poll   |
   |                    |          | component.  If voting has already |
   |                    |          | taken place, these components     |
   |                    |          | MUST include the VOTER property   |
   |                    |          | to indicate each voters current   |
   |                    |          | response.                         |
   |                    |          |                                   |
   | VFREEBUSY          | 0        |                                   |



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   |                    |          |                                   |
   | VJOURNAL           | 0+       | Depending upon the poll mode in   |
   |                    |          | effect there MAY be candidate     |
   |                    |          | components included in the poll   |
   |                    |          | component.  If voting has already |
   |                    |          | taken place, these components     |
   |                    |          | MUST include the VOTER property   |
   |                    |          | to indicate each voters current   |
   |                    |          | response.                         |
   |                    |          |                                   |
   | VTODO              | 0+       | Depending upon the poll mode in   |
   |                    |          | effect there MAY be candidate     |
   |                    |          | components included in the poll   |
   |                    |          | component.  If voting has already |
   |                    |          | taken place, these components     |
   |                    |          | MUST include the VOTER property   |
   |                    |          | to indicate each voters current   |
   |                    |          | response.                         |
   +--------------------+----------+-----------------------------------+

6.3.1.2.1.  Rescheduling a poll

   The "REQUEST" method may be used to reschedule a poll, that is force
   a revote.  A rescheduled poll involves a change to the existing poll
   in terms of its time the components being voted on may have changed.
   If the recipient 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 existing poll, then the "REQUEST" method describes
   a rescheduling of the poll.

6.3.1.2.2.  Updating or Reconfirmation of an Poll

   The "REQUEST" method may be used to update or reconfirm a poll.  An
   update to an existing poll does not involve changes to the time or
   candidates, and might not involve a change to the location or
   description for the poll.  If the recipient 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 poll, then the "REQUEST" method
   describes an update of the poll details, but not a rescheduling of
   the POLL.

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

   The "Organizer" of a poll may also send unsolicited "REQUEST"
   methods.  The unsolicited "REQUEST" methods may be used to update the



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   details of the poll without rescheduling it, to update the "RESPONSE"
   parameter of "Voters", or to reconfirm the poll.

6.3.1.2.3.  Delegating a POll to Another CU

   Some calendar and scheduling systems allow "Voters" to delegate the
   vote to another "Calendar User". iTIP supports this concept using the
   following workflow.  Any "Voter" may delegate their right to vote in
   a poll to another CU.  The implication is that the delegate
   participates in lieu of the original "Voter", NOT in addition to the
   "Voter".  The delegator MUST notify the "Organizer" of this action
   using the steps outlined below.  Implementations may support or
   restrict delegation as they see fit.  For instance, some
   implementations may restrict a delegate from delegating a "REQUEST"
   to another CU.

   The "Delegator" of a poll forwards the existing "REQUEST" to the
   "Delegate".  The "REQUEST" method MUST include a "Voter" property
   with the calendar address of the "Delegate".  The "Delegator" MUST
   also send a "REPLY" method to the "Organizer" with the "Delegator's"
   "Voter" property "DELEGATED-TO" parameter set to the calendar address
   of the "Delegate".  Also, a new "Voter" property for the "Delegate"
   MUST be included and must specify the calendar user address set in
   the "DELEGATED-TO" parameter, as above.

   In response to the request, the "Delegate" MUST send a "REPLY" method
   to the "Organizer", and optionally to the "Delegator".  The "REPLY"
   method SHOULD include the "Voter" property with the "DELEGATED-FROM"
   parameter value of the "Delegator's" calendar address.

   The "Delegator" may continue to receive updates to the poll even
   though they will not be attending.  This is accomplished by the
   "Delegator" setting their "role" attribute to "NON-PARTICIPANT" in
   the "REPLY" to the "Organizer".

6.3.1.2.4.  Changing the Organizer

   The situation may arise where the "Organizer" of a "VPOLL" is no
   longer able to perform the "Organizer" role and abdicates without
   passing on the "Organizer" role to someone else.  When this occurs,
   the "Voters" of the "VPOLL" may use out-of-band mechanisms to
   communicate the situation and agree upon a new "Organizer".  The new
   "Organizer" should then send out a new "REQUEST" with a modified
   version of the "VPOLL" in which the "SEQUENCE" number has been
   incremented and the "ORGANIZER" property has been changed to the new
   "Organizer".





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6.3.1.2.5.  Sending on Behalf of the Organizer

   There are a number of scenarios that support the need for a "Calendar
   User" to act on behalf of the "Organizer" without explicit role
   changing.  This might be the case if the CU designated as "Organizer"
   is sick or unable to perform duties associated with that function.
   In these cases, iTIP supports the notion of one CU acting on behalf
   of another.  Using the "SENT-BY" parameter, a "Calendar User" could
   send an updated "VPOLL" "REQUEST".  In the case where one CU sends on
   behalf of another CU, the "Voter" responses are still directed back
   towards the CU designated as "Organizer".

6.3.1.2.6.  Forwarding to an Uninvited CU

   A "Voter" invited to a "VPOLL" calendar component may send the
   "VPOLL" calendar component to another new CU not previously
   associated with the "VPOLL" calendar component.  The current "Voter"
   participating in the "VPOLL" calendar component does this by
   forwarding the original "REQUEST" method to the new CU.  The new CU
   can send a "REPLY" to the "Organizer" of the "VPOLL" calendar
   component.  The reply contains an "Voter" property for the new CU.

   The "Organizer" ultimately decides whether or not the new CU becomes
   part of the poll and is not obligated to do anything with a "REPLY"
   from a new (uninvited) CU.  If the "Organizer" does not want the new
   CU to be part of the poll, the new "Voter" property is not added to
   the "VPOLL" calendar component.  The "Organizer" MAY send the CU a
   "CANCEL" message to indicate that they will not be added to the poll.
   If the "Organizer" decides to add the new CU, the new "Voter"
   property is added to the "VPOLL" calendar component.  Furthermore,
   the "Organizer" is free to change any "Voter" property parameter from
   the values supplied by the new CU to something the "Organizer"
   considers appropriate.  The "Organizer" SHOULD send the new CU a
   "REQUEST" message to inform them that they have been added.

   When forwarding a "REQUEST" to another CU, the forwarding "Voter"
   MUST NOT make changes to the original message.

6.3.1.2.7.  Updating Voter Status

   The "Organizer" of an poll may also request updated status from one
   or more "Voters".  The "Organizer" sends a "REQUEST" method to the
   "Voter" and sets the "VOTER;RSVP=TRUE" property parameter.  The
   "SEQUENCE" property for the poll 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 updated status.  The recipient SHOULD respond with a "REPLY"
   method indicating their current vote with respect to the "REQUEST".



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6.3.1.3.  REPLY

   The "REPLY" method in a "VPOLL" calendar component is used to respond
   (e.g., accept or decline) to a "REQUEST" or to reply to a delegation
   "REQUEST".  When used to provide a delegation response, the
   "Delegator" SHOULD include the calendar address of the "Delegate" on
   the "DELEGATED-TO" property parameter of the "Delegator's" "Voter"
   property.  The "Delegate" SHOULD include the calendar address of the
   "Delegator" on the "DELEGATED-FROM" property parameter of the
   "Delegate's" "Voter" property.

   The "REPLY" method is also used when processing of a "REQUEST" fails.
   Depending on the value of the "REQUEST-STATUS" property, no action
   may have been performed.

   The "Organizer" of a poll may receive the "REPLY" method from a CU
   not in the original "REQUEST".  For example, a "REPLY" may be
   received from a "Delegate" to a poll.  In addition, the "REPLY"
   method may be received from an unknown CU (a "Party Crasher").  This
   uninvited "Voter" may be accepted, or the "Organizer" may cancel the
   poll for the uninvited "Voter" by sending a "CANCEL" method to the
   uninvited "Voter".

   An "Voter" MAY include a message to the "Organizer" using the
   "COMMENT" property.  For example, if the user indicates a low
   interest and wants to let the "Organizer" know why, the reason can be
   expressed in the "COMMENT" property value.

   The "Organizer" may also receive a "REPLY" from one CU on behalf of
   another.  Like the scenario enumerated above for the "Organizer",
   "Voters" 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
   "0+" or "0 or 1") MUST NOT be changed from those of the original
   request.

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

               +-------------------------------------------+
               | Constraints for a METHOD:REPLY of a VPOLL |
               +-------------------------------------------+

   +--------------------+----------+-----------------------------------+
   | Component/Property | Presence | Comment                           |
   +--------------------+----------+-----------------------------------+
   | METHOD             | 1        | MUST be REPLY.                    |



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   |                    |          |                                   |
   | VPOLL              | 1+       | All components MUST have the same |
   |                    |          | UID.                              |
   |   VOTER            | 1        | MUST be the address of the Voter  |
   |                    |          | replying.                         |
   |   DTSTAMP          | 1        |                                   |
   |   ORGANIZER        | 1        |                                   |
   |   UID              | 1        | MUST be the UID of the original   |
   |                    |          | REQUEST.                          |
   |   SEQUENCE         | 0 or 1   | If non-zero, MUST be the sequence |
   |                    |          | number of the original REQUEST.   |
   |                    |          | MAY be present if 0.              |
   |   ACCEPT-RESPONSE  | 0 or 1   |                                   |
   |   ATTACH           | 0+       |                                   |
   |   CATEGORIES       | 0+       |                                   |
   |   CLASS            | 0 or 1   |                                   |
   |   COMMENT          | 0+       |                                   |
   |   COMPLETED        | 0 or 1   |                                   |
   |   CONTACT          | 0+       |                                   |
   |   CREATED          | 0 or 1   |                                   |
   |   DESCRIPTION      | 0 or 1   |                                   |
   |   DTEND            | 0 or 1   | If present, DURATION MUST NOT be  |
   |                    |          | present.                          |
   |   DTSTART          | 0 or 1   |                                   |
   |   DURATION         | 0 or 1   | If present, DTEND MUST NOT be     |
   |                    |          | present.                          |
   |   GEO              | 0 or 1   |                                   |
   |   LAST-MODIFIED    | 0 or 1   |                                   |
   |   LOCATION         | 0 or 1   |                                   |
   |   POLL-ITEM-ID     | 1+       | One per item being voted on.      |
   |   POLL-MODE        | 0        |                                   |
   |   POLL-PROPERTIES  | 0        |                                   |
   |   PRIORITY         | 0 or 1   |                                   |
   |   RELATED-TO       | 0+       |                                   |
   |   RESOURCES        | 0+       |                                   |
   |   REQUEST-STATUS   | 0+       |                                   |
   |   STATUS           | 0 or 1   |                                   |
   |   SUMMARY          | 0 or 1   |                                   |
   |   TRANSP           | 0 or 1   |                                   |
   |   URL              | 0 or 1   |                                   |
   |   IANA-PROPERTY    | 0+       |                                   |
   |   X-PROPERTY       | 0+       |                                   |
   |                    |          |                                   |
   |   VALARM           | 0        |                                   |
   |                    |          |                                   |
   | VTIMEZONE          | 0 or 1   | MUST be present if any date/time  |
   |                    |          | refers to a timezone.             |
   |                    |          |                                   |



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   | IANA-COMPONENT     | 0+       |                                   |
   | X-COMPONENT        | 0+       |                                   |
   |                    |          |                                   |
   | VEVENT             | 0        |                                   |
   |                    |          |                                   |
   | VFREEBUSY          | 0        |                                   |
   |                    |          |                                   |
   | VJOURNAL           | 0        |                                   |
   |                    |          |                                   |
   | VTODO              | 0        |                                   |
   +--------------------+----------+-----------------------------------+

6.3.1.4.  CANCEL

   The "CANCEL" method in a "VPOLL" calendar component is used to send a
   cancellation notice of an existing poll request to the affected
   "Voters".  The message is sent by the "Organizer" of the poll.

   The "Organizer" MUST send a "CANCEL" message to each "Voter" affected
   by the cancellation.  This can be done using a single "CANCEL"
   message for all "Voters" or by using multiple messages with different
   subsets of the affected "Voters" in each.

   When a "VPOLL" is cancelled, the "SEQUENCE" property value MUST be
   incremented as described in Section 6.2.3.

   Once a CANCEL message has been sent to all voters no further voting
   may take place.  The poll is considered closed.

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

              +--------------------------------------------+
              | Constraints for a METHOD:CANCEL of a VPOLL |
              +--------------------------------------------+

   +--------------------+----------+-----------------------------------+
   | Component/Property | Presence | Comment                           |
   +--------------------+----------+-----------------------------------+
   | METHOD             | 1        | MUST be CANCEL.                   |
   |                    |          |                                   |
   | VPOLL              | 1+       | All must have the same UID.       |
   |   VOTER            | 0+       | MUST include some or all Voters   |
   |                    |          | being removed from the poll.      |
   |                    |          | MUST include some or all Voters   |
   |                    |          | if the entire poll is cancelled.  |
   |   UID              | 1        | MUST be the UID of the original   |
   |                    |          | REQUEST.                          |



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   |   DTSTAMP          | 1        |                                   |
   |   ORGANIZER        | 1        |                                   |
   |   SEQUENCE         | 1        |                                   |
   |   ATTACH           | 0+       |   ACCEPT-RESPONSE                 |
   | 0 or 1             |          |                                   |
   |   COMMENT          | 0+       |                                   |
   |   COMPLETED        | 0 or 1   |                                   |
   |   CATEGORIES       | 0+       |                                   |
   |   CLASS            | 0 or 1   |                                   |
   |   CONTACT          | 0+       |                                   |
   |   CREATED          | 0 or 1   |                                   |
   |   DESCRIPTION      | 0 or 1   |                                   |
   |   DTEND            | 0 or 1   | If present, DURATION MUST NOT be  |
   |                    |          | present.                          |
   |   DTSTART          | 0 or 1   |                                   |
   |   DURATION         | 0 or 1   | If present, DTEND MUST NOT be     |
   |                    |          | present.                          |
   |   GEO              | 0 or 1   |                                   |
   |   LAST-MODIFIED    | 0 or 1   |                                   |
   |   LOCATION         | 0 or 1   |                                   |
   |   POLL-ITEM-ID     | 0        |                                   |
   |   POLL-MODE        | 0        |                                   |
   |   POLL-PROPERTIES  | 0        |                                   |
   |   PRIORITY         | 0 or 1   |                                   |
   |   RELATED-TO       | 0+       |                                   |
   |   RESOURCES        | 0+       |                                   |
   |   STATUS           | 0 or 1   | MUST be set to CANCELLED to       |
   |                    |          | cancel the entire event.  If      |
   |                    |          | uninviting specific Attendees,    |
   |                    |          | then MUST NOT be included.        |
   |   SUMMARY          | 0 or 1   |                                   |
   |   TRANSP           | 0 or 1   |                                   |
   |   URL              | 0 or 1   |                                   |
   |   IANA-PROPERTY    | 0+       |                                   |
   |   X-PROPERTY       | 0+       |                                   |
   |   REQUEST-STATUS   | 0        |                                   |
   |                    |          |                                   |
   |   VALARM           | 0        |                                   |
   |                    |          |                                   |
   | VTIMEZONE          | 0+       | MUST be present if any date/time  |
   |                    |          | refers to a timezone.             |
   |                    |          |                                   |
   | IANA-COMPONENT     | 0+       |                                   |
   | X-COMPONENT        | 0+       |                                   |
   |                    |          |                                   |
   | VTODO              | 0        |                                   |
   |                    |          |                                   |
   | VJOURNAL           | 0        |                                   |



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   |                    |          |                                   |
   | VEVENT             | 0        |                                   |
   |                    |          |                                   |
   | VFREEBUSY          | 0        |                                   |
   +--------------------+----------+-----------------------------------+

6.3.1.5.  REFRESH

   The "REFRESH" method in a "VPOLL" calendar component is used by
   "Voters" of an existing event to request an updated description from
   the poll "Organizer".  The "REFRESH" method must specify the "UID"
   property of the poll to update.  The "Organizer" responds with the
   latest description and version of the poll.

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

              +---------------------------------------------+
              | Constraints for a METHOD:REFRESH of a VPOLL |
              +---------------------------------------------+

   +--------------------+----------+-----------------------------------+
   | Component/Property | Presence | Comment                           |
   +--------------------+----------+-----------------------------------+
   | METHOD             | 1        | MUST be REFRESH.                  |
   |                    |          |                                   |
   | VPOLL              | 1        |                                   |
   |   VOTER            | 1        | MUST be the address of requester. |
   |   DTSTAMP          | 1        |                                   |
   |   ORGANIZER        | 1        |                                   |
   |   UID              | 1        | MUST be the UID associated with   |
   |                    |          | original REQUEST.                 |
   |   COMMENT          | 0+       |                                   |
   |   COMPLETED        | 0        |                                   |
   |   IANA-PROPERTY    | 0+       |                                   |
   |   X-PROPERTY       | 0+       |                                   |
   |   ACCEPT-RESPONSE  | 0        |                                   |
   |   ATTACH           | 0        |                                   |
   |   CATEGORIES       | 0        |                                   |
   |   CLASS            | 0        |                                   |
   |   CONTACT          | 0        |                                   |
   |   CREATED          | 0        |                                   |
   |   DESCRIPTION      | 0        |                                   |
   |   DTEND            | 0        |                                   |
   |   DTSTART          | 0        |                                   |
   |   DURATION         | 0        |                                   |
   |   GEO              | 0        |                                   |
   |   LAST-MODIFIED    | 0        |                                   |



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   |   LOCATION         | 0        |                                   |
   |   POLL-ITEM-ID     | 0        |                                   |
   |   POLL-MODE        | 0        |                                   |
   |   POLL-PROPERTIES  | 0        |                                   |
   |   PRIORITY         | 0        |                                   |
   |   RELATED-TO       | 0        |                                   |
   |   REQUEST-STATUS   | 0        |                                   |
   |   RESOURCES        | 0        |                                   |
   |   SEQUENCE         | 0        |                                   |
   |   STATUS           | 0        |                                   |
   |   SUMMARY          | 0        |                                   |
   |   URL              | 0        |                                   |
   |                    |          |                                   |
   |   VALARM           | 0        |                                   |
   |                    |          |                                   |
   | VTIMEZONE          | 0+       |                                   |
   |                    |          |                                   |
   | IANA-COMPONENT     | 0+       |                                   |
   | X-COMPONENT        | 0+       |                                   |
   |                    |          |                                   |
   | VTODO              | 0        |                                   |
   |                    |          |                                   |
   | VJOURNAL           | 0        |                                   |
   |                    |          |                                   |
   | VEVENT             | 0        |                                   |
   |                    |          |                                   |
   | VFREEBUSY          | 0        |                                   |
   +--------------------+----------+-----------------------------------+

6.3.1.6.  CONFIRM

   The "CONFIRM" method in a "VPOLL" calendar component is used to
   inform recipients that the poll has completed with a result.  The
   "Organizer" MUST be present in the confirmed poll component.
   "Voters" MUST NOT be present.  The selected component(s) according to
   the poll mode MUST also be present in the poll component.  Clients
   receiving this message may store the confirmed items in their
   calendars.

   Once a CONFIRM message has been sent no further voting may take
   place.  The poll is considered closed.

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

              +---------------------------------------------+
              | Constraints for a METHOD:CONFIRM of a VPOLL |
              +---------------------------------------------+



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   +--------------------+----------+-----------------------------------+
   | Component/Property | Presence | Comment                           |
   +--------------------+----------+-----------------------------------+
   | METHOD             | 1        | MUST equal CONFIRM.               |
   |                    |          |                                   |
   | VPOLL              | 1+       |                                   |
   |   COMPLETED        | 1        |                                   |
   |   DTSTAMP          | 1        |                                   |
   |   DTSTART          | 1        |                                   |
   |   ORGANIZER        | 1        |                                   |
   |   SUMMARY          | 1        | Can be null.                      |
   |   VOTER            | 0        |                                   |
   |   UID              | 1        |                                   |
   |   SEQUENCE         | 0 or 1   | MUST be present if value is       |
   |                    |          | greater than 0; MAY be present if |
   |                    |          | 0.                                |
   |   ACCEPT-RESPONSE  | 0        |                                   |
   |   ATTACH           | 0        |                                   |
   |   CATEGORIES       | 0        |                                   |
   |   CLASS            | 0        |                                   |
   |   COMMENT          | 0+       |                                   |
   |   CONTACT          | 0 or 1   |                                   |
   |   CREATED          | 0 or 1   |                                   |
   |   DESCRIPTION      | 0 or 1   | Can be null.                      |
   |   DTEND            | 0 or 1   | If present, DURATION MUST NOT be  |
   |                    |          | present.                          |
   |   DURATION         | 0 or 1   | If present, DTEND MUST NOT be     |
   |                    |          | present.                          |
   |   LAST-MODIFIED    | 0 or 1   |                                   |
   |   POLL-ITEM-ID     | 0        |                                   |
   |   POLL-MODE        | 0 or 1   |                                   |
   |   POLL-PROPERTIES  | 0        |                                   |
   |   PRIORITY         | 0 or 1   |                                   |
   |   RELATED-TO       | 0+       |                                   |
   |   RESOURCES        | 0+       |                                   |
   |   STATUS           | 0 or 1   | MAY be one of                     |
   |                    |          | TENTATIVE/CONFIRMED/CANCELLED.    |
   |   URL              | 0 or 1   |                                   |
   |   IANA-PROPERTY    | 0+       |                                   |
   |   X-PROPERTY       | 0+       |                                   |
   |   VOTER            | 0        |                                   |
   |   REQUEST-STATUS   | 0        |                                   |
   |                    |          |                                   |
   |   VALARM           | 0+       |                                   |
   |                    |          |                                   |
   | VEVENT             | 0+       | All selected components MAY be    |
   |                    |          | present.                          |
   |                    |          |                                   |



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   | VFREEBUSY          | 0        |                                   |
   |                    |          |                                   |
   | VJOURNAL           | 0+       | All selected components MAY be    |
   |                    |          | present.                          |
   |                    |          |                                   |
   | VTODO              | 0+       | All selected components MAY be    |
   |                    |          | present.                          |
   |                    |          |                                   |
   | VTIMEZONE          | 0+       | MUST be present if any date/time  |
   |                    |          | refers to a timezone.             |
   |                    |          |                                   |
   | IANA-COMPONENT     | 0+       |                                   |
   | X-COMPONENT        | 0+       |                                   |
   +--------------------+----------+-----------------------------------+

6.3.1.7.  POLLSTATUS

   The "POLLSTATUS" method in a "VPOLL" calendar component is used to
   inform recipients of the current status of the poll in a compact
   manner.  The "Organizer" MUST be present in the confirmed poll
   component.  "Voters" MUST NOT be present.  The selected component(s)
   according to the poll mode MUST also be present in the poll
   component.  Clients receiving this message may store the confirmed
   items in their calendars.

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

              +---------------------------------------------+
              | Constraints for a METHOD:CONFIRM of a VPOLL |
              +---------------------------------------------+

   +--------------------+----------+-----------------------------------+
   | Component/Property | Presence | Comment                           |
   +--------------------+----------+-----------------------------------+
   | METHOD             | 1        | MUST equal POLLSTATUS.            |
   |                    |          |                                   |
   | VPOLL              | 1+       |                                   |
   |   COMPLETED        | 0 or 1   | Only present for a completed poll |
   |   DTSTAMP          | 1        |                                   |
   |   DTSTART          | 0 or 1   |                                   |
   |   ORGANIZER        | 1        |                                   |
   |   SUMMARY          | 1        | Can be null.                      |
   |   VOTER            | 1+       |                                   |
   |   UID              | 1        |                                   |
   |   SEQUENCE         | 0 or 1   | MUST be present if value is       |
   |                    |          | greater than 0; MAY be present if |
   |                    |          | 0.                                |



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   |   ACCEPT-RESPONSE  | 0        |                                   |
   |   ATTACH           | 0        |                                   |
   |   CATEGORIES       | 0        |                                   |
   |   CLASS            | 0        |                                   |
   |   COMMENT          | 0+       |                                   |
   |   CONTACT          | 0        |                                   |
   |   CREATED          | 0 or 1   |                                   |
   |   DESCRIPTION      | 0 or 1   | Can be null.                      |
   |   DTEND            | 0 or 1   | If present, DURATION MUST NOT be  |
   |                    |          | present.                          |
   |   DURATION         | 0 or 1   | If present, DTEND MUST NOT be     |
   |                    |          | present.                          |
   |   LAST-MODIFIED    | 0 or 1   |                                   |
   |   POLL-ITEM-ID     | 0        |                                   |
   |   POLL-MODE        | 0 or 1   |                                   |
   |   POLL-PROPERTIES  | 0        |                                   |
   |   PRIORITY         | 0 or 1   |                                   |
   |   RELATED-TO       | 0+       |                                   |
   |   RESOURCES        | 0+       |                                   |
   |   STATUS           | 0 or 1   | MAY be one of                     |
   |                    |          | TENTATIVE/CONFIRMED/CANCELLED.    |
   |   URL              | 0 or 1   |                                   |
   |   IANA-PROPERTY    | 0+       |                                   |
   |   X-PROPERTY       | 0+       |                                   |
   |   VOTER            | 0        |                                   |
   |   REQUEST-STATUS   | 0        |                                   |
   |                    |          |                                   |
   |   VALARM           | 0+       |                                   |
   |                    |          |                                   |
   | VEVENT             | 0+       | All candidate components MUST be  |
   |                    |          | present but in a reduced form     |
   |                    |          | sufficient to provide the voting  |
   |                    |          | status.                           |
   |                    |          |                                   |
   | VFREEBUSY          | 0        |                                   |
   |                    |          |                                   |
   | VJOURNAL           | 0+       | All candidate components MUST be  |
   |                    |          | present but in a reduced form     |
   |                    |          | sufficient to provide the voting  |
   |                    |          | status.                           |
   |                    |          |                                   |
   | VTODO              | 0+       | All candidate components MUST be  |
   |                    |          | present but in a reduced form     |
   |                    |          | sufficient to provide the voting  |
   |                    |          | status.                           |
   |                    |          |                                   |
   | VTIMEZONE          | 0+       | MUST be present if any date/time  |
   |                    |          | refers to a timezone.             |



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   |                    |          |                                   |
   | IANA-COMPONENT     | 0+       |                                   |
   | X-COMPONENT        | 0+       |                                   |
   +--------------------+----------+-----------------------------------+


7.  CalDAV Extensions

   This specification extends [RFC4791] in that it defines a new
   component and new iCalendar properties to be supported and requires
   extra definitions related to time-ranges and reports.

7.1.  Calendar Collection Properties

   This section defines new CalDAV properties for calendar collections.

7.1.1.  CALDAV:vpoll-supported-component-set

   Name:  vpoll-supported-component-set

   Namespace:  urn:ietf:params:xml:ns:caldav

   Purpose:  Specifies the calendar component types (e.g., VEVENT,
      VTODO, etc.) that may be included in a VPOLL component.

   Conformance:  This property MAY be defined on any calendar
      collection.  If defined, it MUST be protected and SHOULD NOT be
      returned by a PROPFIND DAV:allprop request (as defined in Section
      12.14.1 of [RFC2518]).

   Description:  The CALDAV:vpoll-supported-component-set property is
      used to specify restrictions on the calendar component types that
      VPOLL components may contain in a calendar collection.  Any
      attempt by the client to store VPOLL components with component
      types not listed in this property, if it exists, MUST result in an
      error, with the CALDAV:vpoll-supported-component precondition
      Section 7.2 being violated.  Since this property is protected, it
      cannot be changed by clients using a PROPPATCH request.  However,
      clients can initialize the value of this property when creating a
      new calendar collection with MKCALENDAR.  In the absence of this
      property, the server MUST accept all component types, and the
      client can assume that all component types are accepted.

   Definition:

            <!ELEMENT vpoll-supported-component-set (comp+)>





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   Example:

            <C:vpoll-supported-component-set
                xmlns:C="urn:ietf:params:xml:ns:caldav">
              <C:comp name="VEVENT"/>
              <C:comp name="VTODO"/>
            </C:vpoll-supported-component-set>


7.1.2.  CALDAV:vpoll-max-items

   Name:  vpoll-max-items

   Namespace:  urn:ietf:params:xml:ns:caldav

   Purpose:  Provides a numeric value indicating the maximum number of
      items that may be contained in any instance of a VPOLL calendar
      object resource stored in the calendar collection.

   Conformance:  This property MAY be defined on any calendar
      collection.  If defined, it MUST be protected and SHOULD NOT be
      returned by a PROPFIND DAV:allprop request (as defined in Section
      12.14.1 of [RFC2518]).

   Description:  The CALDAV:vpoll-max-items is used to specify a numeric
      value that indicates the maximum number of iCalendar components in
      any one instance of a VPOLL calendar object resource stored in a
      calendar collection.  Any attempt to store a calendar object
      resource with more components per instance than this value MUST
      result in an error, with the CALDAV: vpoll-max-items precondition
      Section 7.2 being violated.  In the absence of this property, the
      client can assume that the server can handle any number of items
      in a VPOLL calendar component.

   Definition:

            <!ELEMENT vpoll-max-items (#PCDATA)>
            PCDATA value: a numeric value (integer greater than zero)


   Example:

            <C:vpoll-max-items
                 xmlns:C="urn:ietf:params:xml:ns:caldav"
            >25</C:vpoll-max-items>






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7.1.3.  CALDAV:vpoll-max-active

   Name:  vpoll-max-active

   Namespace:  urn:ietf:params:xml:ns:caldav

   Purpose:  Provides a numeric value indicating the maximum number of
      active vpolls at any one time.

   Conformance:  This property MAY be defined on any calendar
      collection.  If defined, it MUST be protected and SHOULD NOT be
      returned by a PROPFIND DAV:allprop request (as defined in Section
      12.14.1 of [RFC2518]).

   Description:  The CALDAV:vpoll-max-active is used to specify a
      numeric value that indicates the maximum number of active VPOLLs
      at any one time.  Any attempt to store a new active VPOLL calendar
      object resource which results in exceeding this limit MUST result
      in an error, with the CALDAV: vpoll-max-active precondition
      Section 7.2 being violated.  In the absence of this property, the
      client can assume that the server can handle any number of active
      VPOLLs.

   Definition:

            <!ELEMENT vpoll-max-active (#PCDATA)>
            PCDATA value: a numeric value (integer greater than zero)


   Example:

            <C:vpoll-max-active
                 xmlns:C="urn:ietf:params:xml:ns:caldav"
            >25</C:vpoll-max-active>


7.1.4.  CALDAV:vpoll-max-voters

   Name:  vpoll-max-voters

   Namespace:  urn:ietf:params:xml:ns:caldav

   Purpose:  Provides a numeric value indicating the maximum number of
      voters for any instance of a VPOLL calendar object resource stored
      in the calendar collection.






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   Conformance:  This property MAY be defined on any calendar
      collection.  If defined, it MUST be protected and SHOULD NOT be
      returned by a PROPFIND DAV:allprop request (as defined in Section
      12.14.1 of [RFC2518]).

   Description:  The CALDAV:vpoll-max-voters is used to specify a
      numeric value that indicates the maximum number of VOTER
      properties for any one instance of a VPOLL calendar object
      resource stored in a calendar collection.  Any attempt to store a
      calendar object resource with more VOTER properties per instance
      than this value MUST result in an error, with the CALDAV: vpoll-
      max-voters precondition Section 7.2 being violated.  In the
      absence of this property, the client can assume that the server
      can handle any number of voters in a VPOLL calendar component.

   Definition:

            <!ELEMENT vpoll-max-voters (#PCDATA)>
            PCDATA value: a numeric value (integer greater than zero)


   Example:

            <C:vpoll-max-voters
                 xmlns:C="urn:ietf:params:xml:ns:caldav"
            >25</C:vpoll-max-voters>


7.1.5.  CalDAV:even-more-properties

   1.  List of poll modes

   2.  Combination of components - For a caldav server, a capability dav
       property similar to support component sets which specifies what
       sets of icalendar components are supports for voting, for
       example, only support VEVENTs.

   3.  Limits:Size of individual resources

   4.  Limits:Size of total vpoll

   5.  Limits:Max voting period

   6.  Limits:itip/~itip

   7.  Limits:remote attendee/voter capable





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   8.  poll options - e.g "vpoll-basic"

7.2.  Additional Preconditions for PUT, COPY, and MOVE

   This specification creates additional Preconditions for PUT, COPY,
   and MOVE methods.  These preconditions apply when a PUT operation of
   a VPOLL calendar object resource into a calendar collection occurs,
   or when a COPY or MOVE operation of a calendar object resource into a
   calendar collection occurs, or when a COPY or MOVE operation occurs
   on a calendar collection.

   The new preconditions are:

   (CALDAV:vpoll-supported-component):  The VPOLL resource submitted in
      the PUT request, or targeted by a COPY or MOVE request, MUST
      contain a type of calendar component that is supported in the
      targeted calendar collection;

   (CALDAV:vpoll-max-items):  The VPOLL resource submitted in the PUT
      request, or targeted by a COPY or MOVE request, MUST have a number
      of sub-components (excluding VTIMEZONE) less than or equal to the
      value of the CALDAV:vpoll-max-items property value Section 7.1.2
      on the calendar collection where the resource will be stored;;

   (CALDAV:vpoll-max-active):  The PUT request, or COPY or MOVE request,
      MUST not result in the number of active VPOLLsbeing greater than
      the value of the CALDAV:vpoll-max-active property value
      Section 7.1.3 on the calendar collection where the resource will
      be stored;;

   (CALDAV:vpoll-max-voters):  The VPOLL resource submitted in the PUT
      request, or targeted by a COPY or MOVE request, MUST have a number
      of VOTER properties less than or equal to the value of the CALDAV:
      vpoll-max-voters property value Section 7.1.4 on the calendar
      collection where the resource will be stored;;

7.3.  CalDAV:calendar-query Report

   This allows the retrieval of VPOLLs and their included components.
   The query specification allows queries to be directed at the
   contained sub-components

7.3.1.  Example: Partial Retrieval of VPOLL

   In this example, the client requests the server to return specific
   components and properties of the VPOLL components that overlap the
   time range from December 4, 2012, at 00:00:00 A.M. UTC to December 5,
   2012, at 00:00:00 A.M. UTC.  In addition, the DAV:getetag property is



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   also requested and returned as part of the response.  Note that due
   to the CALDAV: calendar-data element restrictions, the DTSTAMP
   property in VPOLL components has not been returned, and the only
   property returned in the VCALENDAR object is VERSION.

      >> Request <<

      REPORT /cyrus/work/ HTTP/1.1
      Host: cal.example.com
      Depth: 1
      Content-Type: application/xml; charset="utf-8"
      Content-Length: xxxx

      <?xml version="1.0" encoding="utf-8" ?>
      <C:calendar-query xmlns:D="DAV:"
                    xmlns:C="urn:ietf:params:xml:ns:caldav">
        <D:prop>
          <D:getetag/>
          <C:calendar-data>
            <C:comp name="VCALENDAR">
              <C:prop name="VERSION"/>
              <C:comp name="VPOLL">
                <C:prop name="SUMMARY"/>
                <C:prop name="UID"/>
                <C:prop name="DTSTART"/>
                <C:prop name="DTEND"/>
                <C:prop name="DURATION"/>
              </C:comp>
            </C:comp>
          </C:calendar-data>
        </D:prop>
        <C:filter>
          <C:comp-filter name="VCALENDAR">
            <C:comp-filter name="VPOLL">
              <C:time-range start="20121204T000000Z"
                            end="20121205T000000Z"/>
            </C:comp-filter>
          </C:comp-filter>
        </C:filter>
      </C:calendar-query>

      >> Response <<

      HTTP/1.1 207 Multi-Status
      Date: Sat, 11 Nov 2012 09:32:12 GMT
      Content-Type: application/xml; charset="utf-8"
      Content-Length: xxxx




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      <?xml version="1.0" encoding="utf-8" ?>
      <D:multistatus xmlns:D="DAV:"
                 xmlns:C="urn:ietf:params:xml:ns:caldav">
        <D:response>
          <D:href>http://cal.example.com/cyrus/work/poll2.ics</D:href>
          <D:propstat>
            <D:prop>
              <D:getetag>"fffff-abcd2"</D:getetag>
              <C:calendar-data>BEGIN:VCALENDAR
      VERSION:2.0
      BEGIN:VEVENT
      DTSTART;TZID=US/Eastern:20121202T120000
      DURATION:PT4D
      SUMMARY:Poll #2
      UID:00959BC664CA650E933C892C@example.com
      END:VPOLL
      END:VCALENDAR
      </C:calendar-data>
            </D:prop>
            <D:status>HTTP/1.1 200 OK</D:status>
          </D:propstat>
        </D:response>
        <D:response>
          <D:href>http://cal.example.com/cyrus/work/poll3.ics</D:href>
          <D:propstat>
            <D:prop>
              <D:getetag>"fffff-abcd3"</D:getetag>
              <C:calendar-data>BEGIN:VCALENDAR
      VERSION:2.0
      PRODID:-//Example Corp.//CalDAV Client//EN
      BEGIN:VPOLL
      DTSTART;TZID=US/Eastern:20121204T100000
      DURATION:PT4D
      SUMMARY:Poll #3
      UID:DC6C50A017428C5216A2F1CD@example.com
      END:VPOLL
      END:VCALENDAR
      </C:calendar-data>
            </D:prop>
            <D:status>HTTP/1.1 200 OK</D:status>
          </D:propstat>
        </D:response>
      </D:multistatus>








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7.3.2.  Example: Retrieval of Vpolls by sub-component Time Range

   In this example, the client requests the server to return the VPOLL
   components that have an alarm trigger scheduled in the specified time
   range.

      >> Request <<

      REPORT /cyrus/work/ HTTP/1.1
      Host: cal.example.com
      Depth: 1
      Content-Type: application/xml; charset="utf-8"
      Content-Length: xxxx

      <?xml version="1.0" encoding="utf-8" ?>
      <C:calendar-query xmlns:C="urn:ietf:params:xml:ns:caldav">
        <D:prop xmlns:D="DAV:">
          <D:getetag/>
          <C:calendar-data/>
        </D:prop>
        <C:filter>
          <C:comp-filter name="VCALENDAR">
            <C:comp-filter name="VPOLL">
              <C:comp-filter name="*">
                <C:time-range start="20121206T100000Z"
                                end="20121207T100000Z"/>
              </C:comp-filter>
            </C:comp-filter>
          </C:comp-filter>
        </C:filter>
      </C:calendar-query>

      >> Response <<

      HTTP/1.1 207 Multi-Status
      Date: Sat, 11 Nov 2012 09:32:12 GMT
      Content-Type: application/xml; charset="utf-8"
      Content-Length: xxxx

      <?xml version="1.0" encoding="utf-8" ?>
      <D:multistatus xmlns:D="DAV:"
                     xmlns:C="urn:ietf:params:xml:ns:caldav">
        <D:response>
          <D:href>http://cal.example.com/cyrus/work/poll4.ics</D:href>
          <D:propstat>
            <D:prop>
              <D:getetag>"fffff-abcd4"</D:getetag>
              <C:calendar-data>BEGIN:VCALENDAR



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      VERSION:2.0
      PRODID:-//Example Corp.//CalDAV Client//EN
      BEGIN:VPOLL
      DTSTAMP:20121205T235300Z
      DTEND;TZID=US/Eastern:20121206T120000
      LAST-MODIFIED:20121205T235308Z
      SEQUENCE:1
      SUMMARY:Poll #4
      UID:E10BA47467C5C69BB74E8720@example.com
      BEGIN:VEVENT
      ...
      END:VEVENT
      BEGIN:VEVENT
      ...
      END:VEVENT
      BEGIN:VEVENT
      ...
      DTSTART;TZID=US/Eastern:20120606T150000
      ...
      END:VEVENT
      END:VPOLL
      END:VCALENDAR
      </C:calendar-data>
            </D:prop>
            <D:status>HTTP/1.1 200 OK</D:status>
          </D:propstat>
        </D:response>
      </D:multistatus>

7.4.  CalDAV time ranges

   Section 9.9 "CALDAV:time-range XML Element" in [RFC4791] describes
   how to specify time ranges to limit the set of calendar components
   returned by the server.  This specification extends [RFC4791] to
   describe the meaning of time ranges for VPOLL

   A VPOLL component is said to overlap a given time range if the
   condition for the corresponding component state specified in the
   table below is satisfied.  The conditions depend on the presence of
   the DTSTART, DURATION, DTEND, COMPLETED and CREATED properties in the
   VPOLL component.  Note that, as specified above, the DTEND value MUST
   be a DATE-TIME value equal to or after the DTSTART value if
   specified.








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   +-------------------------------------------------------------------+
   | VPOLL has the DTSTART property?                                   |
   |   +---------------------------------------------------------------+
   |   |   VPOLL has the DURATION property?                            |
   |   |   +-----------------------------------------------------------+
   |   |   | VPOLL has the DTEND property?                             |
   |   |   |   +-------------------------------------------------------+
   |   |   |   | VPOLL has the COMPLETED property?                     |
   |   |   |   |   +---------------------------------------------------+
   |   |   |   |   | VPOLL has the CREATED property?                   |
   |   |   |   |   |   +-----------------------------------------------+
   |   |   |   |   |   | Condition to evaluate                         |
   +---+---+---+---+---+-----------------------------------------------+
   | Y | Y | N | * | * | (start  <= DTSTART+DURATION)  AND             |
   |   |   |   |   |   | ((end   >  DTSTART)  OR                       |
   |   |   |   |   |   |  (end   >= DTSTART+DURATION))                 |
   +---+---+---+---+---+-----------------------------------------------+
   | Y | N | Y | * | * | ((start <  DTEND)    OR  (start <= DTSTART))  |
   |   |   |   |   |   | AND                                           |
   |   |   |   |   |   | ((end   >  DTSTART)  OR  (end   >= DTEND))    |
   +---+---+---+---+---+-----------------------------------------------+
   | Y | N | N | * | * | (start  <= DTSTART)  AND (end >  DTSTART)     |
   +---+---+---+---+---+-----------------------------------------------+
   | N | N | Y | * | * | (start  <  DTEND)    AND (end >= DTEND)       |
   +---+---+---+---+---+-----------------------------------------------+
   | N | N | N | Y | Y | ((start <= CREATED)  OR  (start <= COMPLETED))|
   |   |   |   |   |   | AND                                           |
   |   |   |   |   |   | ((end   >= CREATED)  OR  (end   >= COMPLETED))|
   +---+---+---+---+---+-----------------------------------------------+
   | N | N | N | Y | N | (start  <= COMPLETED) AND (end  >= COMPLETED) |
   +---+---+---+---+---+-----------------------------------------------+
   | N | N | N | N | Y | (end    >  CREATED)                           |
   +---+---+---+---+---+-----------------------------------------------+
   | N | N | N | N | N | TRUE                                          |
   +---+---+---+---+---+-----------------------------------------------+

7.5.  freebusy reports

   How do outstanding VPOLLs affect freebusy requests?  Still an
   outstanding issue.  Transparency is client controlled - server/client
   implementations may provide defaults.  We previously ruled out TRANSP
   in VPOLL.  Following are some notes.

   It seems appropriate to allow end-users to specify that they wish
   time to be reserved when voting in favor of a given event.

   The default for VPOLL should be that all contained events are marked
   transparent - note the default for VEVENT is OPAQUE so should all



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   contained VEVENTS have the TRANSP added when created?

   Should we create temporary related events to block time if the user
   requests?  Or just treat the VPOLL as a psuedo-collection and add it
   to the freebusy set?


8.  Notes

   Various collected notes to be fitted in somewhere...

   1.   What about POLL-WINNER?

           pollwinner = "POLL-WINNER" pollwinnerparams ":" text CRLF
           pollwinnerparams = *(";" other-param)
           ; Used with a STATUS:CONFIRMED VPOLL to indicate which
           ; components have been confirmed

   2.   Need to add example of freebusy in response

   BEGIN:VCALENDAR
   VERSION:2.0
   PRODID:-//BedeworkCaldavTest//BedeworkCaldavTest
   METHOD: REPLY
   BEGIN:VPOLL
   ORGANIZER:mailto:douglm@mysite.edu
   VOTER:mailto:eric@example.com
   UID:sched01-1234567890
   DTSTAMP:20120101T010000Z
   SEQUENCE:0
   SUMMARY:What to do this week
   BEGIN:VFREEBUSY
   .......
   END:VFREEBUSY
   END:VPOLL
   END:VCALENDAR

   3.   Define LINK types - n

   4.   Keep polls around after confirm or cancel.  Use STATUS parameter
        inside VPOLL with states: NEEDS-ACTION, CANCELLED, CLOSED,
        CONFIRMED.  Use POLL-ITEM-ID to identify the confirmed
        component.

   5.   A good client will remember the DTSTAMP of each VOTER and not
        allow an older DTSTAMP to override a newer DTSTAMP.





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   6.   Fill out VOTER with the rest of the ATTENDEE properties
        (SCHEDULE-STATUS, SCHEDULE-AGENT)

   7.   Use STATUS to mark active, canceled, completed.

   8.   Client updates their VOTER property as in the POLLSTATUS
        example.

   9.   LINK or URL in POLL-MODE?

   10.  Use RELATED-TO in a icalendar component such as VEVENT or VTODO
        with a new reltypeparam to specify the relationship to a VPOLL.
        May need a reltypeparam for both an active and confirmed poll,
        or may only need one reltypeparam.  Need to pick a new
        reltypeparam name.

   11.  Like POLL-PROPERTIES, but for a caldav server, a dav property
        that specify what icalender properties this server supports for
        voting.

   12.  Need to do a section on what Notifications to support.
        A. VPOLL is about to end and you haven't voted on it yet.

   13.  Need to pick: SCHEDULED-AGENT=NONE or STATUS:DRAFT or a non-
        calendar collection for drafts.  Each one has it's pluses and
        minuses.

   14.  What to do with changes to STATUS:CONFIRMED?  Allow them or not?
        What do to that poll had a winning event or todo.

   15.  Need to write down what isn't valid in a VPOLL.
        a.  Can't change POLL-MODE

   16.  Can a user create a poll with scheduled events where that user's
        isn't the organizer of the poll?  So is there a requierment that
        the account that poll is on is able to create each one of the
        resources in the poll? i.e.  I can't create a poll with a set of
        events where I am just the attendee of the polls.  Are there any
        other restrictions for components in a VPOLL?

   17.  Ability to reject VPOLL.

   18.  Limits on number of outstanding VPOLL.

   19.  Add a dav property which will specify when a poll will expire
        and therfore be deleted from the server.





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   20.  Guide for ATTENDEE roles chair, NON-PARTICIPANT etc

   21.  Shared Calendars
        Only voters (or delegates) can manipulate votes.

   22.  When voting on existing event - winning properties ONLY are
        merged in to the real event.

   23.  On confirm - send itip if appropriate (PUBLISH) - all non-
        participating - shared - feeds
        Organizer can specify where result is?
        Confirm can specify that itip is sent - ITIP / NONE - parameter
        ? on POLL-WINNER


9.  Security Considerations

   Applications using these property need to be aware of the risks
   entailed in using the URIs provided as values.  See [RFC3986] for a
   discussion of the security considerations relating to URIs.


10.  IANA Considerations

10.1.  Parameter Registrations

   This document defines the following new iCalendar property parameters
   to be added to the registry defined in Section 8.2.4 of [RFC5545]:

         +--------------------+---------+------------------------+
         | Property Parameter | Status  | Reference              |
         +--------------------+---------+------------------------+
         | PUBLIC-COMMENT     | Current | RFCXXXX, Section 4.1.1 |
         | RESPONSE           | Current | RFCXXXX, Section 4.1.2 |
         | STAY-INFORMED      | Current | RFCXXXX, Section 4.1.3 |
         +--------------------+---------+------------------------+

10.2.  Property Registrations

   This document defines the following new iCalendar properties to be
   added to the registry defined in Section 8.2.3 of [RFC5545]:










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          +-----------------+---------+------------------------+
          | Property        | Status  | Reference              |
          +-----------------+---------+------------------------+
          | ACCEPT-RESPONSE | Current | RFCXXXX, Section 4.2.1 |
          | POLL-ITEM-ID    | Current | RFCXXXX, Section 4.2.2 |
          | POLL-MODE       | Current | RFCXXXX, Section 4.2.3 |
          | VOTER           | Current | RFCXXXX, Section 4.2.5 |
          +-----------------+---------+------------------------+

10.3.  POLL-MODE Registration Template

   A poll mode is defined by completing the following template.

   Poll mode name:  The name of the poll mode.

   Purpose:  The purpose of the poll mode.  Give a short but clear
      description.

   Reference:  A reference to the RFC in which the poll mode is defined

10.4.  POLL-MODE Registrations

   This document defines the following registered poll modes.

   +----------+--------------------------------------------+-----------+
   | Poll     | Purpose                                    | Reference |
   | mode     |                                            |           |
   | name     |                                            |           |
   +----------+--------------------------------------------+-----------+
   | BASIC    | To provide simple voting for a single      | Current   |
   |          | outcome from a number of candidates.       |           |
   +----------+--------------------------------------------+-----------+


11.  Acknowledgements

   The authors would like to thank the members of the Calendaring and
   Scheduling Consortium Freebusy technical committee and the following
   individuals for contributing their ideas and support:

   ...

   The authors would also like to thank the Calendaring and Scheduling
   Consortium for advice with this specification.







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12.  Normative References

   [I-D.daboo-icalendar-extensions]
              Daboo, C., "New Properties for iCalendar",
              draft-daboo-icalendar-extensions-05 (work in progress),
              June 2012.

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119, March 1997.

   [RFC2434]  Narten, T. and H. Alvestrand, "Guidelines for Writing an
              IANA Considerations Section in RFCs", BCP 26, RFC 2434,
              October 1998.

   [RFC2518]  Goland, Y., Whitehead, E., Faizi, A., Carter, S., and D.
              Jensen, "HTTP Extensions for Distributed Authoring --
              WEBDAV", RFC 2518, February 1999.

   [RFC3688]  Mealling, M., "The IETF XML Registry", BCP 81, RFC 3688,
              January 2004.

   [RFC3986]  Berners-Lee, T., Fielding, R., and L. Masinter, "Uniform
              Resource Identifier (URI): Generic Syntax", STD 66,
              RFC 3986, January 2005.

   [RFC4589]  Schulzrinne, H. and H. Tschofenig, "Location Types
              Registry", RFC 4589, July 2006.

   [RFC4791]  Daboo, C., Desruisseaux, B., and L. Dusseault,
              "Calendaring Extensions to WebDAV (CalDAV)", RFC 4791,
              March 2007.

   [RFC5545]  Desruisseaux, B., "Internet Calendaring and Scheduling
              Core Object Specification (iCalendar)", RFC 5545,
              September 2009.

   [RFC5546]  Daboo, C., "iCalendar Transport-Independent
              Interoperability Protocol (iTIP)", RFC 5546,
              December 2009.

   [RFC6047]  Melnikov, A., "iCalendar Message-Based Interoperability
              Protocol (iMIP)", RFC 6047, December 2010.

   [W3C.REC-xml-20060816]
              Yergeau, F., Paoli, J., Sperberg-McQueen, C., Maler, E.,
              and T. Bray, "Extensible Markup Language (XML) 1.0 (Fourth
              Edition)", World Wide Web Consortium FirstEdition REC-xml-
              20060816, August 2006,



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Internet-Draft                    VPOLL                     January 2013


              <http://www.w3.org/TR/2006/REC-xml-20060816>.


Appendix A.  Open issues

   Issue 1:  What's the issue with that?


Appendix B.  Change log

   2012-11-02 MD Initial version


Authors' Addresses

   Eric York (editor)
   Apple Inc.
   1 Infinite Loop
   Cupertino, CA  95014
   USA

   Email: eyork@apple.com
   URI:   http://www.apple.com/


   Cyrus Daboo (editor)
   Apple Inc.
   1 Infinite Loop
   Cupertino, CA  95014
   USA

   Email: cyrus@daboo.name
   URI:   http://www.apple.com/


   Michael Douglass (editor)
   Rensselaer Polytechnic Institute
   110 8th Street
   Troy, NY  12180
   USA

   Email: douglm@rpi.edu
   URI:   http://www.rpi.edu/








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