Network Working Group E. York, Ed.
Internet-Draft C. Daboo, Ed.
Intended status: Standards Track Apple Inc.
Expires: September 5, 2014 M. Douglass, Ed.
RPI
March 4, 2014

VPOLL: Consensus Scheduling Component for iCalendar
draft-york-vpoll-01

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 Task Force (IETF). Note that other groups may also distribute working documents as Internet-Drafts. The list of current Internet-Drafts is at http://datatracker.ietf.org/drafts/current/.

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

This Internet-Draft will expire on September 5, 2014.

Copyright Notice

Copyright (c) 2014 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 Provisions Relating to IETF Documents (http://trustee.ietf.org/license-info) in effect on the date of publication of this document. Please review these documents carefully, as they describe your rights and restrictions with respect to this document. Code Components extracted from this document must include Simplified BSD License text as described in Section 4.e of the Trust Legal Provisions and are provided without warranty as described in the Simplified BSD License.


Table of Contents

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 availability. 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 approaches such 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 usually 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 for this process and allow calendar clients and servers and 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:

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.
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 a different date and or time for the meeting.

       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
       BEGIN:VEVENT.......(with a poll-item-id=1)
       END:VEVENT
       BEGIN:VEVENT.......(with a poll-item-id=2)
       END:VEVENT
       BEGIN:VEVENT.......(with a poll-item-id=3)
       END:VEVENT
       END:VPOLL
       END:VCALENDAR

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

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 iMip or 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 for that voter for all components being voted on. In our example, if Eric responds and votes 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.

       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

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

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

       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

An example:

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. A VPOLL can be completed (and effectively closed for voting) by sending an iTip REQUEST message with the VPOLL STATUS property set to COMPLETED.

The poll winner is confirmed by sending a final iTip REQUEST message with the VPOLL STATUS property set to CONFIRMED. In this case the VPOLL component contains all the events being voted on along with a POLL-WINNER property to identify the winning event.

       BEGIN:VCALENDAR
       VERSION:2.0
       PRODID:-//Example//Example
       METHOD: REQUEST
       BEGIN:VPOLL
       ORGANIZER:mailto:douglm@example.com
       UID:sched01-1234567890
       DTSTAMP:20120101T030000Z
       COMPLETED:20120101T030000Z
       SEQUENCE:0
       SUMMARY:What to do this week
       STATUS:CONFIRMED
       POLL-WINNER:3
       BEGIN:VEVENT.......(with a poll-item-id=1)
       END:VEVENT
       BEGIN:VEVENT.......(with a poll-item-id=2)
       END:VEVENT
       BEGIN:VEVENT.......(with a poll-item-id=3)
       END:VEVENT
       END:VPOLL
       END:VCALENDAR

The VPOLL confirmation example:

4. iCalendar Extensions

4.1. Updated Property Parameters

4.1.1. Updated Relation Type Value

Relationship parameter type values are defined in section 3.2.15. of [RFC5545]. This specification updates that type to include the new relationship value POLL to provide a link to the VPOLL component in which the current component appears.

This property parameter is redefined by the following notation:

            reltypeparam       /= "RELTYPE" "=" "POLL"
                  ; Property value is a VPOLL uid
                  
Format Definition:
Description:
This parameter can be specified on a property that references another related calendar component. The new parameter value indicates gthat the associated proeprty references a VPOLL component which contains the current component.

4.1.2. Updated Status Value

Status property values are defined in section 3.8.1.11. of [RFC5545]. This specification updates that type to valid VPOLL status values.

This property parameter is redefined by the following notation:

            statvalue /= statvalue-poll
                    ; Status values for "VPOLL".
            statvalue-poll = "IN-PROCESS"
                           / "COMPLETED"  ; Poll has closed,
                                          ; nothing has been chosen yet
                           / "CONFIRMED"  ; Poll has closed and
                                          ;winning items confirmed
                           / "CANCELLED"
                  
Format Definition:

4.2. New Property Parameters

4.2.1. Public-Comment

This parameter is defined by the following notation:

   public-comment-param = "PUBLIC-COMMENT=" DQUOTE text DQUOTE
                  
Parameter name:
PUBLIC-COMMENT
Purpose:
To allow voters to provide a public comment in their response.
Format Definition:
Description:
This parameter can be specified on the POLL-ITEM-ID property to allow a voter to add some commentary visible to all voters.

4.2.2. Response

This parameter is defined by the following notation:

    responseparam = "RESPONSE=" integer
          ; integer value 0..100
                  
Parameter name:
RESPONSE
Purpose:
To specify a response vote.
Format Definition:
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:

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).

4.2.3. Stay-Informed

This parameter is defined by the following notation:

    stayinformedparam = "STAY-INFORMED" "=" boolean
                  
Parameter name:
STAY-INFORMED
Purpose:
To specify the voter also wants to be added as an ATTENDEE when the poll is confirmed.
Format Definition:
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.

4.3. New Properties

4.3.1. Accept-Response

This property is defined by the following notation:

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

  acceptresponseparams = *(";" other-param)
                  
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:

4.3.2. Poll-Item-Id

This property is defined by the following notation:

          pollitemid = "POLL-ITEM-ID" pollitemdparams ":"
                     integer CRLF

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

                  
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:
INTEGER
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.
POLL-ITEM-ID SHOULD be a unique small integer 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:

4.3.3. Poll-Mode

This property is defined by the following notation:

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

          pollmodeparams = *(";" other-param)

                  
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.
Format Definition:

4.3.4. Poll-properties

This property is defined by the following notation:

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

          pollpropparams = *(";" other-param)

                  
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:

4.3.5. Poll-Winner

This property is defined by the following notation:

          pollwinner = "POLL-WINNER" pollwinnerparams ":"
                    integer CRLF

          pollwinnerparams = *(";" other-param)

          ; Used with a STATUS:CONFIRMED VPOLL to indicate which
          ; components have been confirmed

                  
Property name:
POLL-WINNER
Purpose:
This property is used in a basic mode VPOLL to indicate which of the VPOLL sub-components won.
Value type:
INTEGER
Property Parameters:
Non-standard parameters can be specified on this property.
Conformance:
This property MAY be specified in a VPOLL component.
Description:
For poll confirmation each child component MUST have a POLL-ITEM-ID property. For basic mode the VPOLL component SHOULD have a POLL_WINNER property which MUST correspond to one of the POLL-ITEM-ID properties and indicates which sub-component was the winner.
Format Definition:

4.3.6. Voter

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 are OPTIONAL, but MUST NOT occur
                    ; more than once. They are defined in RFC6638
                    ;
                    (";" scheduleagentparam) /
                    (";" scheduleforcesendparam) /
                    (";" schedulestatusparam) /

                    ;
                    ; The following is OPTIONAL,
                    ; and MAY occur more than once.
                    ;
                    (";" other-param)
                    ;
              )

                  
Property name:
VOTER
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:
Note 1
RSVP=TRUE MAY be used by the organizer to force the voter to reset their state and re-vote.
Note 2
scheduleagentparam, scheduleforcesendparam and schedulestatusparam are all related to CalDAV scheduling and are defined in [RFC6638]. Their semantics are exactly as defined in that specification.

4.4. VPOLL Component

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 / rstatus / related /
             resources / voter / x-prop / iana-prop
             ;
             ; The following is OPTIONAL, it SHOULD appear
             ; once for the confirmation of a BASIC mode
             ; VPOLL. Other modes may define differing
             ; requirements.
             ;
             pollwinner /
             ;
             )
               
Component name:
VPOLL
Purpose:
This component provides a mechanism by which voters can vote on provided choices.
Format Definition:
Description:
This component provides a mechanism by which voters can vote on provided choices. The outcome depends upon the POLL-MODE in effect.
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 9.3.

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 has the following property requirements:

POLL-ITEM-ID:
Each contained sub-component that is being voted upon MUST contain a POLL-ITEM_ID property which is unique within the context of the POLL. The value MUST NOT be reused when events are removed and/or added to the poll.
POLL-WINNER:
On confirmation of the poll this property MUST be present and identifies the winning component.

5.1.2. Outcome reporting

To confirm the winner the POLL-WINNER property must be present and the STATUS MUST be set to CONFIRMED.

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.
REFRESH The organizer returns a METHOD:REQUEST with the current full state, or a METHOD:CANCEL 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.

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 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.

Method Description
PUBLISH Post notification of an poll. Used primarily as a method of advertising the existence of a poll.
REQUEST To make a request for a poll. This is an explicit invitation to one or more voters. Poll requests are also used to update, change or confirm 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.

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
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 COMPLETED/CONFIRMED/CANCELLED.
URL 0 or 1
IANA-PROPERTY 0+
X-PROPERTY 0+
VOTER 0
REQUEST-STATUS 0
VALARM 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
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:

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
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 COMPLETED/CONFIRMED/CANCELLED.
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
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 a 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 details of the poll without rescheduling it, to update the "RESPONSE" parameter of "Voters", or to reconfirm the poll.

6.3.1.2.3. Confirmation of a Poll

The "REQUEST" method may be used to confirm a poll, that is announce the winner in BASIC mode. The STATUS MUST be set to CONFIRMED and for BASIC mode a VPOLL POLL-WINNER property must be provided with the poll-id of the winning component.

6.3.1.2.4. Closing a Poll

The "REQUEST" method may be used to close a poll, that is indicate voting is completed. The STATUS MUST be set to COMPLETED.

6.3.1.2.5. 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".

6.3.1.2.6. 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".

6.3.1.2.7. 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".

6.3.1.2.8. 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.

6.3.1.2.9. 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".

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.
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.
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.
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
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
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. 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:POLLSTATUS 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.
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+
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.
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:supported-vpoll-component-sets

         <!ELEMENT supported-vpoll-component-sets
                (supported-vpoll-component-set*) >

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


         <C:supported-vpoll-component-sets
              xmlns:C="urn:ietf:params:xml:ns:caldav">

           <!-- VPOLLs with VEVENT, VFREEBUSY or VTODO -->
           <C:supported-vpoll-component-set>
             <C:comp name="VEVENT" />
             <C:comp name="VFREEBUSY" />
             <C:comp name="VTODO" />
           </C:supported-vpoll-component-set>

           <!-- VPOLLs with just VEVENT or VFREEBUSY -->
           <C:supported-vpoll-component-set>
             <C:comp name="VEVENT" />
             <C:comp name="VFREEBUSY" />
           </C:supported-vpoll-component-set>

           <!-- VPOLLs with just VEVENT -->
           <C:supported-vpoll-component-set>
             <C:comp name="VEVENT" />
           </C:supported-vpoll-component-set>

           <!-- VPOLLs with just VTODO -->
           <C:supported-vpoll-component-set>
             <C:comp name="VTODO" />
           </C:supported-vpoll-component-set>
         </C:supported-vpoll-component-sets>

Name:
supported-vpoll-component-sets
Namespace:
urn:ietf:params:xml:ns:caldav
Purpose:
Specifies the calendar component types (e.g., VEVENT, VTODO, etc.) and combination of types 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:supported-vpoll-component-sets property is used to specify restrictions on the calendar component types that VPOLL components may contain in a calendar collection.
It also specifies the combination of allowed component types.
Any attempt by the client to store VPOLL components with component types or combinations of types not listed in this property, if it exists, MUST result in an error, with the CALDAV:supported-vpoll-component-sets 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:
Example:

7.1.2. CALDAV:vpoll-max-items

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

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

7.1.3. CALDAV:vpoll-max-active

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

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

7.1.4. CALDAV:vpoll-max-voters

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

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

7.1.5. CalDAV:even-more-properties

  1. vpoll-supported-mode 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:supported-vpoll-component-sets):
The VPOLL resource submitted in the PUT request, or targeted by a COPY or MOVE request, MUST contain a type or combination 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. For VPOLL queries this feature is disallowed. Time-range queries can only target the vpoll component itself.

7.3.1. Example: Partial Retrieval of VPOLL

   >> 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

   <?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>

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 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.

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

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

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.

8. 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.

9. IANA Considerations

9.1. 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 4.2.1
RESPONSE Current RFCXXXX, Section 4.2.2
STAY-INFORMED Current RFCXXXX, Section 4.2.3

9.2. Property Registrations

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

Property Status Reference
ACCEPT-RESPONSE Current RFCXXXX, Section 4.3.1
POLL-ITEM-ID Current RFCXXXX, Section 4.3.2
POLL-MODE Current RFCXXXX, Section 4.3.3
VOTER Current RFCXXXX, Section 4.3.6

9.3. 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

9.4. POLL-MODE Registrations

This document defines the following registered poll modes.

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

10. 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.

11. Normative References

[I-D.daboo-icalendar-extensions] Daboo, C., "New Properties for iCalendar", Internet-Draft draft-daboo-icalendar-extensions-06, January 2013.
[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.
[RFC6638] Daboo, C. and B. Desruisseaux, "Scheduling Extensions to CalDAV", RFC 6638, June 2012.
[W3C.REC-xml-20060816] Yergeau, F., Paoli, J., Bray, T., Maler, E. and C. Sperberg-McQueen, "Extensible Markup Language (XML) 1.0 (Fourth Edition)", World Wide Web Consortium FirstEdition REC-xml-20060816, August 2006.

Appendix A. Open issues

                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
              

Notifications:
Need to do a section on what Notifications to support.
A. VPOLL is about to end and you haven't voted on it yet.
Instead reuse VALARMS to notify the user?
Future: Restarting a confirmed/completed VPOLL
What to do with changes to STATUS:CONFIRMED? Allow them or not? What do to that poll had a winning event or todo.
Stress VPOLL UID MUST be unique
Changing status back from CONFIRMED MUST adjust status of any events booked as a result of confirmation.
MUST winning event be cancelled for POLL-MODE basic? No - VOTER has indicated now unable to attend - want to revote
Future: Voting on a confirmed/completed VPOLL
Can a VOTER vote after completion? May be unable to attend and wants to indicate. Requires retention of VPOLL
retention period
Removed status
ORGANIZER/ATTENDEE validity
Can a user create a poll with scheduled events where that user's isn't the organizer of the poll? So is there a requirement 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 events. Are there any other restrictions for components in a VPOLL?
Add to security consideration
Update to existing event after poll confirm
When voting on existing event - winning properties ONLY are merged in to the real event.
Need to write down what isn't valid in a VPOLL

a. Can't change POLL-MODE
Guide for ATTENDEE roles

chair, NON-PARTICIPANT etc
? - some iTip notes
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
Need to add example of freebusy in response

Appendix B. Change log

V01: 2013-08-07 MD

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/