[Docs] [txt|pdf|xml|html] [Tracker] [WG] [Email] [Diff1] [Diff2] [Nits]

Versions: 00 01 02 03 04 05 draft-ietf-calext-availability

Network Working Group                                           C. Daboo
Internet-Draft                                                     Apple
Updates: 5545,5546 (if approved)                             M. Douglass
Intended status: Standards Track                                     RPI
Expires: August 3, 2014                                 January 30, 2014


                         Calendar Availability
                  draft-daboo-calendar-availability-05

Abstract

   This document specifies a new iCalendar calendar component that
   allows the publication of available and unavailable time periods
   associated with a calendar user.  This component can be used in
   standard iCalendar free-busy lookups, including iTIP free-busy
   requests, to generate repeating blocks of available or busy time with
   exceptions as needed.

   This document also defines extensions to CalDAV calendar-access and
   calendar-auto-schedule which specify how this new calendar component
   should be used when doing free-busy time evaluation in CalDAV.

Editorial Note (To be removed by RFC Editor before publication)

   Discussion of this specification is taking place on the mailing list
   http://lists.osafoundation.org/mailman/listinfo/ietf-caldav .

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 August 3, 2014.







Daboo & Douglass         Expires August 3, 2014                 [Page 1]


Internet-Draft            Calendar Availability             January 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  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Conventions Used in This Document . . . . . . . . . . . . . .   3
   3.  iCalendar Extensions  . . . . . . . . . . . . . . . . . . . .   4
     3.1.  Vavailability Component . . . . . . . . . . . . . . . . .   4
     3.2.  Busy Time Type  . . . . . . . . . . . . . . . . . . . . .  10
   4.  Combining Vavailability components  . . . . . . . . . . . . .  10
   5.  Calculating Free-Busy Time  . . . . . . . . . . . . . . . . .  11
     5.1.  Examples  . . . . . . . . . . . . . . . . . . . . . . . .  12
   6.  CalDAV Extensions . . . . . . . . . . . . . . . . . . . . . .  14
     6.1.  CalDAV Requirements Overview  . . . . . . . . . . . . . .  14
     6.2.  New features in CalDAV  . . . . . . . . . . . . . . . . .  15
   7.  Security Considerations . . . . . . . . . . . . . . . . . . .  18
   8.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  18
     8.1.  Component Registrations . . . . . . . . . . . . . . . . .  18
     8.2.  Property Registrations  . . . . . . . . . . . . . . . . .  18
   9.  Acknowledgments . . . . . . . . . . . . . . . . . . . . . . .  18
   10. Normative References  . . . . . . . . . . . . . . . . . . . .  18
   Appendix A.  Example Calendar #1  . . . . . . . . . . . . . . . .  19
   Appendix B.  Change History (To be removed by RFC Editor before
                publication) . . . . . . . . . . . . . . . . . . . .  21
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  22

1.  Introduction

   Often calendar users have regular periods of time when they are
   either available to be scheduled or always unavailable.  For example,
   an office worker will often wish to only appear free to their work
   colleagues during normal 'office hours' (e.g., Monday through Friday,
   9 am through 5 pm).  Or, a university professor may only be available
   to students during a set period of time (e.g., Thursday afternoons, 2
   pm through 5 pm during term time only).  Ideally users should be able



Daboo & Douglass         Expires August 3, 2014                 [Page 2]


Internet-Draft            Calendar Availability             January 2014


   to specify such periods directly via their calendar user agent, and
   have them automatically considered as part of the normal free-busy
   lookup for that user.  In addition it should be possible to present
   different periods of available time depending on which user is making
   the request.

   iCalendar [RFC5545] defines a "VFREEBUSY" component that can be used
   to represent fixed busy time periods, but it does does not provide a
   way to specify a repeating period of available or unavailable time.
   Since repeating patterns are often the case, "VFREEBUSY" components
   are not sufficient to solve this problem.

   This specification defines a new type of iCalendar calendar component
   that can be used to publish user availability.

   CalDAV [RFC4791] provides a way for calendar users to access and
   manage calendar data and exchange this data via scheduling
   operations.  As part of this, the CalDAV calendar-access [RFC4791]
   feature provides a CALDAV:free-busy-query REPORT that returns free-
   busy information for a calendar collection or hierarchy of calendar
   collections.  Also, the CalDAV calendar-auto-schedule [RFC6638]
   feature allows free-busy information for a calendar user to be
   determined.  Both of these operations involve examining user
   calendars for events that 'block time', with the blocked out periods
   being returned in a "VFREEBUSY" component.

   This specification extends the CalDAV calendar-access and CalDAV
   calendar-auto-schedule features to allow the new iCalendar
   availability components to be stored and manipulated, and to allow
   free-busy lookups to use the information from any such components, if
   present.

2.  Conventions 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] .

   When XML element types in the namespaces "DAV:" and
   "urn:ietf:params:xml:ns:caldav" are referenced in this document
   outside of the context of an XML fragment, the string "DAV:" and
   "CALDAV:" will be prefixed to the element type names respectively.








Daboo & Douglass         Expires August 3, 2014                 [Page 3]


Internet-Draft            Calendar Availability             January 2014


3.  iCalendar Extensions

   This specification adds a new "VAVAILABILITY" calendar component to
   iCalendar.  The "VAVAILABILITY" component is itself a container for
   new "AVAILABLE" sub-components.

   The purpose of the "VAVAILABILITY" calendar component is to provide a
   grouping of available time information over a specific range of time.
   Within that there are specific time ranges that are marked as
   available via a set of "AVAILABLE" calendar sub-components.  Together
   these can be used to specify available time that can repeat over set
   periods of time, and which can vary over time.

3.1.  Vavailability Component

   Component Name:  VAVAILABILITY

   Purpose:  Provide a grouping of component properties that describe
      the availability associated with a calendar user.

   Format Definition:  A "VAVAILABILITY" calendar component is defined
      by the following notation:

          availabilityc  = "BEGIN" ":" "VAVAILABILITY" CRLF
                           availabilityprop *availablec
                           "END" ":" "VAVAILABILITY" CRLF

          availabilityprop  = *(
                            ;
                            ; the following are REQUIRED,
                            ; but MUST NOT occur more than once
                            ;
                            dtstamp / uid
                            ;
                            ; the following are OPTIONAL,
                            ; but MUST NOT occur more than once
                            ;
                            busytype / class / created / description /
                            dtstart / last-mod / organizer / priority /
                            seq / summary / url /
                            ;
                            ; either 'dtend' or 'duration' MAY appear
                            ; once, but 'dtend' and 'duration' MUST
                            ; NOT occur in the same 'availabilityprop'.
                            ;
                            dtend / duration /
                            ;
                            ; the following are OPTIONAL,



Daboo & Douglass         Expires August 3, 2014                 [Page 4]


Internet-Draft            Calendar Availability             January 2014


                            ; and MAY occur more than once
                            ;
                            categories / comment / contact /
                            x-prop / iana-prop
                            ;
                            )

          availablec  = "BEGIN" ":" "AVAILABLE" CRLF
                        availableprop
                        "END" ":" "AVAILABLE" CRLF

          availableprop  = *(
                         ;
                         ; the following are REQUIRED,
                         ; but MUST NOT occur more than once
                         ;
                         dtstamp / dtstart / uid /
                         ;
                         ; either 'dtend' or 'duration' MAY appear
                         ; once, but 'dtend' and 'duration' MUST NOT
                         ; occur in the same 'availableprop'.
                         ; 'duration' MUST NOT be present if 'dtstart'
                         ; is not present
                         ;
                         dtend / duration /
                         ;
                         ; the following are OPTIONAL,
                         ; but MUST NOT occur more than once
                         ;
                         created / description / last-mod /
                         recurid / rrule / summary /
                         ;
                         ; the following are OPTIONAL,
                         ; and MAY occur more than once
                         ;
                         categories / comment / contact / exdate /
                         rdate / x-prop / iana-prop

                         )

   Description:  A "VAVAILABILITY" component indicates a period of time
      within which availability information is provided.  A
      "VAVAILABILITY" component can specify a start time and an end time
      or duration.  If "DTSTART" is not present, then the start time is
      unbounded.  If "DTEND" or "DURATION" are not present, then the end
      time is unbounded.  Within the specified time period, availability
      defaults to a free-busy type of "BUSY-UNAVAILABLE", except for any
      time periods corresponding to "AVAILABLE" sub-components.



Daboo & Douglass         Expires August 3, 2014                 [Page 5]


Internet-Draft            Calendar Availability             January 2014


      "AVAILABLE" sub-components are used to indicate periods of free
      time within the time range of the enclosing "VAVAILABILITY"
      component.  "AVAILABLE" sub-components MAY include recurrence
      properties to specify recurring periods of time, which may be
      overridden using normal recurrence behavior (i.e., use of the
      "RECURRENCE-ID" property).

      If specified, the "DTSTART" and "DTEND" properties in
      "VAVAILABILITY" components and "AVAILABLE" sub-components MUST be
      "DATE-TIME" values specified as either date with UTC time or date
      with local time and a time zone reference.

      If any property with a "DATE-TIME" value is present in a
      "VAVAILABILITY" component or any of its "AVAILABLE" sub-
      components, and that property includes a "TZID" parameter, then
      the iCalendar object containing the "VAVAILABILITY" component MUST
      contain "VTIMEZONE" components corresponding to each unique "TZID"
      parameter value.

      When used to publish available time, the "ORGANIZER" property
      specifies the calendar user associated with the published
      available time.

      If the "PRIORITY" property is specified in "VAVAILABILITY"
      components it is used to determine how that component is combined
      with other "VAVAILABILITY" components.  See Section 4

      Other calendar properties MAY be specified in "VAVAILABILITY" or
      "AVAILABLE" components and are considered attributes of the marked
      block of time.  Their usage is application specific.  For example,
      the "LOCATION" property may be used to indicate that a person is
      available in one location for part of the week and another
      location for another part.

   Example:  The following is an example of a "VAVAILABILITY" calendar
      component used to represent the availability of a user always
      available Monday through Friday, 9:00 AM to 5:00 PM in the America
      /Montreal time zone:













Daboo & Douglass         Expires August 3, 2014                 [Page 6]


Internet-Draft            Calendar Availability             January 2014


        BEGIN:VAVAILABILITY
        ORGANIZER:mailto:bernard@example.com
        UID:vavail-1@example.com
        DTSTAMP:20111005T133225Z
        BEGIN:AVAILABLE
        UID:avail-1-A@example.com
        SUMMARY:Monday to Friday from 9:00 to 17:00
        DTSTART;TZID=America/Montreal:20111002T090000
        DTEND;TZID=America/Montreal:20111002T170000
        RRULE:FREQ=WEEKLY;BYDAY=MO,TU,WE,TH,FR
        END:AVAILABLE
        END:VAVAILABILITY

      The following is an example of a "VAVAILABILITY" calendar
      component used to represent the availability of a user available
      Monday through Thursday, 9:00 AM to 5:00 PM at the main office,
      and Friday 9:00 AM to 12:00 PM in the branch office in the America
      /Montreal time zone between October 2nd and December 2nd 2011:

        BEGIN:VAVAILABILITY
        ORGANIZER:mailto:bernard@example.com
        UID:vavail-1@example.com
        DTSTAMP:20111005T133225Z
        DTSTART;TZID=America/Montreal:20111002T000000
        DTEND;TZID=America/Montreal:20111202T000000
        BEGIN:AVAILABLE
        UID:avail-1-A@example.com
        SUMMARY:Monday to Thursday from 9:00 to 17:00
        DTSTART;TZID=America/Montreal:20111002T090000
        DTEND;TZID=America/Montreal:20111002T170000
        RRULE:FREQ=WEEKLY;BYDAY=MO,TU,WE,TH
        LOCATION:Main Office
        END:AVAILABLE
        BEGIN:AVAILABLE
        UID:avail-1-B@example.com
        SUMMARY:Friday from 9:00 to 12:00
        DTSTART;TZID=America/Montreal:20111006T090000
        DTEND;TZID=America/Montreal:20111006T120000
        RRULE:FREQ=WEEKLY
        LOCATION:Branch Office
        END:AVAILABLE
        END:VAVAILABILITY

      The following is an example of three "VAVAILABILITY" calendar
      components used to represent the availability of a traveling
      worker: Monday through Friday, 9:00 AM to 5:00 PM each day.
      However, for three weeks the calendar user is working in Montreal,
      then one week in Los Angeles, then back to Montreal.  Note that



Daboo & Douglass         Expires August 3, 2014                 [Page 7]


Internet-Draft            Calendar Availability             January 2014


      each overall period is covered by separate "VAVAILABILITY"
      components.  The last of these has no DTEND so continues on "for
      ever".  This example shows one way "blocks" of available time can
      be represented.  See Section 4 for another approach using
      priority.














































Daboo & Douglass         Expires August 3, 2014                 [Page 8]


Internet-Draft            Calendar Availability             January 2014


        BEGIN:VAVAILABILITY
        ORGANIZER:mailto:bernard@example.com
        UID:vavail-1@example.com
        DTSTAMP:20111005T133225Z
        DTSTART;TZID=America/Montreal:20111002T000000
        DTEND;TZID=America/Montreal:20111023T030000
        BEGIN:AVAILABLE
        UID:avail-1-A@example.com
        SUMMARY:Monday to Friday from 9:00 to 17:00
        DTSTART;TZID=America/Montreal:20111002T090000
        DTEND;TZID=America/Montreal:20111002T170000
        RRULE:FREQ=WEEKLY;BYDAY=MO,TU,WE,TH,FR
        LOCATION:Montreal
        END:AVAILABLE
        END:VAVAILABILITY
        BEGIN:VAVAILABILITY
        ORGANIZER:mailto:bernard@example.com
        UID:vavail-2@example.com
        DTSTAMP:20111005T133225Z
        DTSTART;TZID=America/Los_Angeles:20111023T000000
        DTEND;TZID=America/Los_Angeles:20111030T000000
        BEGIN:AVAILABLE
        UID:avail-2-A@example.com
        SUMMARY:Monday to Friday from 9:00 to 17:00
        DTSTART;TZID=America/Los_Angeles:20111023T090000
        DTEND;TZID=America/Los_Angeles:20111023T170000
        RRULE:FREQ=WEEKLY;BYDAY=MO,TU,WE,TH,FR
        LOCATION:Los Angeles
        END:AVAILABLE
        END:VAVAILABILITY
        BEGIN:VAVAILABILITY
        ORGANIZER:mailto:bernard@example.com
        UID:vavail-3@example.com
        DTSTAMP:20111005T133225Z
        DTSTART;TZID=America/Montreal:20111030T030000
        BEGIN:AVAILABLE
        UID:avail-3-A@example.com
        SUMMARY:Monday to Friday from 9:00 to 17:00
        DTSTART;TZID=America/Montreal:20111030T090000
        DTEND;TZID=America/Montreal:20111030T170000
        RRULE:FREQ=WEEKLY;BYDAY=MO,TU,WE,TH,FR
        LOCATION:Montreal
        END:AVAILABLE
        END:VAVAILABILITY







Daboo & Douglass         Expires August 3, 2014                 [Page 9]


Internet-Draft            Calendar Availability             January 2014


3.2.  Busy Time Type

   Property Name:  BUSYTYPE

   Purpose:  This property specifies the default busy time type.

   Value Type:  TEXT

   Property Parameters:  IANA and non-standard property parameters can
      be specified on this property.

   Conformance:  This property can be specified within "VAVAILABILITY"
      calendar components.

   Format Definition:  This property is defined by the following
      notation:

        busytype      = "BUSYTYPE" busytypeparam ":" busytypevalue CRLF

        busytypeparam = *(";" other-param)

        busytypevalue = "BUSY" / "BUSY-UNAVAILABLE" /
                        "BUSY-TENTATIVE" / iana-token / x-name
                        ; Default is "BUSY-UNAVAILABLE".

   Description:  This property is used to specify the default busy time
      type.  The values correspond to those used by the "FBTYPE"
      parameter used on a "FREEBUSY" property, with the exception that
      the "FREE" value is not used in this property.  If not specified
      on a component that allows this property, the default is "BUSY-
      UNAVAILABLE".

   Example:  The following is an example of this property:

        BUSYTYPE:BUSY

4.  Combining Vavailability components

   The Vavailability component allows a calendar user to describe their
   availability over extended periods of time through the use of
   recurrence patterns.  This availability may be relatively constant
   from year to year.

   However, there is usually some degree of irregularity, as people take
   vacations or perhaps spend a few weeks at a different office.  For
   that period of time there can be a need to redefine their
   availability.




Daboo & Douglass         Expires August 3, 2014                [Page 10]


Internet-Draft            Calendar Availability             January 2014


   Rather than modify their existing vavailability, the "PRIORITY"
   property allows new vavailability components to be provided which
   override others of lower ordinal priority.  Note that iCalendar
   [RFC5545] defines the "PRIORITY" property such that a value of 0 is
   undefined, 1 is the highest priority and 9 is the lowest.

   When combining vavailability components, an absence of a "PRIORITY"
   property or a value of 0 implies the lowest level of priority.  If
   two or more vavailability components have the same PRIORITY value,
   then their AVAILABILITY components which fall within the date range
   of interest are combined.  It is up to the creator of such components
   to ensure that combining them produces a consistent and expected
   result.

   To calculate the available time, order the intersecting
   "VAVAILABILITY" components by priority, those with no "PRIORITY" or a
   priority value of 0 first, then in decreasing order of priority that
   is, an increasing "PRIORITY" value.

   Step through the resulting list of "VAVAILABILITY" components.  For
   each, the time range covered by the "VAVAILABILITY" component is set
   to busy and then portions of it defined by the "AVAILABLE" components
   in the "VAVAILABILITY" component are set to free.

   Note that, if any VAVAILABILITY component completely covers the date
   range of interest, then any lower priority VAVAILABILITY components
   may be ignored.

5.  Calculating Free-Busy Time

   This section describes how free-busy time information for a calendar
   user is calculated in the presence of "VAVAILABILITY" calendar
   components.

   An iCalendar "VFREEBUSY" component is used to convey "rolled-up"
   free-busy time information for a calendar user.  This can be
   generated as the result of an iTIP free-busy [RFC5546] request or
   through some other mechanism (e.g., a CalDAV calendar-access CALDAV
   :free-busy-query REPORT).

   When one or more "VAVAILABILITY" components are present and intersect
   the time-range for the free-busy request, first available time is
   calculated, as outlined in Section 4.  Once that is done, regular
   "VEVENT" and "VFREEBUSY" components can be "overlaid" in the usual
   way to block out additional time.

   An example procedure for this is as follows:




Daboo & Douglass         Expires August 3, 2014                [Page 11]


Internet-Draft            Calendar Availability             January 2014


   1.  Initially mark the entire period of the free-busy request as
       free.

   2.  For each "VAVAILABILITY" component ordered by PRIORITY:

       1.  Determine if the "VAVAILABILITY" intersects the time-range of
           the free-busy request.  If not ignore it.

       2.  Determine if the "VAVAILABILITY" is completely overridden by
           a higher priority component.  If so ignore it.

       3.  For the time period covered by the "VAVAILABILITY" component,
           mark time in the free-busy request result set as busy, using
           the busy time type derived from the "BUSYTYPE" property in
           the "VAVAILABILITY" component.

   3.  For each remaining "VAVAILABILITY" component in the same order:

       1.  For each "AVAILABLE" component in the "VAVAILABILITY"
           component:

           1.  Expand all recurring instances, taking into account
               overridden instances, ignoring instances or parts of
               instances that fall outside of the free-busy request
               time-range or the time period specified by the
               "VAVAILABILITY" component.

           2.  For each instance, mark the corresponding time in the
               free-busy request result set as free.

   4.  For each "VEVENT" or "VFREEBUSY" component apply normal free-busy
       processing within the free-busy request time-range.

5.1.  Examples

   In the examples below a table is used to represent time slots for the
   period of a free-busy request.  Each time slot is two hours long.
   The column header represents the hours from midnight local time.
   Each row below the column headers represents a step in the free-busy
   result set determination, following the procedure outlined above.

   Each cell in the rows below the column header contains a single
   character that represents the free-busy type for the corresponding
   time period at the end of the process step represented by the row.
   The characters in the row are:






Daboo & Douglass         Expires August 3, 2014                [Page 12]


Internet-Draft            Calendar Availability             January 2014


     +-----------+--------------------------------------------------+
     | Character | Meaning                                          |
     +-----------+--------------------------------------------------+
     | F         | Represents "FREE" time in that slot.             |
     | B         | Represents "BUSY" time in that slot.             |
     | U         | Represents "BUSY-UNAVAILABLE" time in that slot. |
     | T         | Represents "BUSY-TENTATIVE" time in that slot.   |
     +-----------+--------------------------------------------------+

5.1.1.  Simple Example

   A free-busy request for Monday, 6th November 2011, midnight to
   midnight in the America/Montreal timezone.

   The user's calendar is as shown in Appendix A . This includes one
   "VAVAILABILITY" component giving available time within the requested
   time-range of 8:00 AM to 6:00 PM, together with one "VEVENT"
   component representing a two hour meeting starting at 12:00 PM.

   +------+----+----+----+----+----+----+----+----+----+----+----+----+
   | Step | 0  | 2  | 4  | 6  | 8  | 10 | 12 | 14 | 16 | 18 | 20 | 22 |
   +------+----+----+----+----+----+----+----+----+----+----+----+----+
   | 1.   | F  | F  | F  | F  | F  | F  | F  | F  | F  | F  | F  | F  |
   | 2.   | U  | U  | U  | U  | U  | U  | U  | U  | U  | U  | U  | U  |
   | 3.   | U  | U  | U  | U  | F  | F  | F  | F  | F  | U  | U  | U  |
   | 4.   | U  | U  | U  | U  | F  | F  | B  | F  | F  | U  | U  | U  |
   +------+----+----+----+----+----+----+----+----+----+----+----+----+

5.1.2.  Further Example

   The following is another way to represent the availability of the
   traveling worker shown above.  Here we represent their base
   availability of Monday through Friday, 9:00 AM to 5:00 PM each day
   with a "VAVAILABILITY" with defaulted PRIORITY.  For the three weeks
   the calendar user is working in Montreal we represent it with an
   overriding "VAVAILABILITY" component with priority 1.















Daboo & Douglass         Expires August 3, 2014                [Page 13]


Internet-Draft            Calendar Availability             January 2014


        BEGIN:VAVAILABILITY
        ORGANIZER:mailto:bernard@example.com
        UID:vavail-1@example.com
        DTSTAMP:20111005T133225Z
        DTSTART;TZID=America/Montreal:20111002T000000
        BEGIN:AVAILABLE
        UID:avail-1-A@example.com
        SUMMARY:Monday to Friday from 9:00 to 17:00
        DTSTART;TZID=America/Montreal:20111002T090000
        DTEND;TZID=America/Montreal:20111002T170000
        RRULE:FREQ=WEEKLY;BYDAY=MO,TU,WE,TH,FR
        LOCATION:Montreal
        END:AVAILABLE
        END:VAVAILABILITY
        BEGIN:VAVAILABILITY
        ORGANIZER:mailto:bernard@example.com
        UID:vavail-2@example.com
        DTSTAMP:20111005T133225Z
        DTSTART;TZID=America/Los_Angeles:20111023T000000
        DTEND;TZID=America/Los_Angeles:20111030T000000
        BEGIN:AVAILABLE
        UID:avail-2-A@example.com
        SUMMARY:Monday to Friday from 9:00 to 17:00
        DTSTART;TZID=America/Los_Angeles:20111023T090000
        DTEND;TZID=America/Los_Angeles:20111023T170000
        PRIORITY:1
        RRULE:FREQ=WEEKLY;BYDAY=MO,TU,WE,TH,FR
        LOCATION:Los Angeles
        END:AVAILABLE
        END:VAVAILABILITY

6.  CalDAV Extensions

6.1.  CalDAV Requirements Overview

   This section lists what functionality is required of a CalDAV server
   which supports this extension.  A server:

   o  MUST support "VAVAILABILITY" components in a calendar collection
      resource if the CALDAV calendar-access feature is supported, which
      includes advertising it in CALDAV;supported-calendar-component-set
      properties on calendars;

   o  MUST support CALDAV:free-busy-query REPORTs that aggregate the
      information in any "VAVAILABILITY" components in the calendar
      collections targeted by the request;





Daboo & Douglass         Expires August 3, 2014                [Page 14]


Internet-Draft            Calendar Availability             January 2014


   o  MUST support "VAVAILABILITY" components stored in a CALDAV
      :calendar-availability WebDAV property on a CALDAV scheduling
      inbox collection if the CALDAV calendar-auto-schedule feature is
      supported;

   o  MUST support iTIP [RFC5546] free-busy requests that aggregate the
      information in any "VAVAILABILITY" components in calendar
      collections that contribute to free-busy, or in any
      "VAVAILABILITY" components stored in the CALDAV:calendar-
      availability in the CALDAV scheduling inbox collection of the
      calendar user targeted by the iTIP free-busy request, if the
      CalDAV calendar-auto-schedule feature is available.

6.2.  New features in CalDAV

6.2.1.  Calendar Availability Support

   A server supporting the features described in this document MUST
   include "calendar-availability" as a field in the DAV response header
   from an OPTIONS request on any resource that supports any calendar
   properties, reports, method, or privilege.  A value of "calendar-
   availability" in the DAV response header MUST indicate that the
   server supports all MUST level requirements specified in this
   document.

6.2.1.1.  Example: Using OPTIONS for the Discovery of Calendar
          Availability Support

   >> Request <<

      OPTIONS /home/bernard/calendars/ HTTP/1.1
      Host: cal.example.com

   >> Response <<

      HTTP/1.1 200 OK
      Allow: OPTIONS, GET, HEAD, POST, PUT, DELETE, TRACE, COPY, MOVE
      Allow: PROPFIND, PROPPATCH, LOCK, UNLOCK, REPORT, ACL
      DAV: 1, 2, 3, access-control, calendar-access,
       calendar-availability
      Date: Fri, 11 Nov 2005 09:32:12 GMT
      Content-Length: 0

   In this example, the OPTIONS method returns the value "calendar-
   availability" in the DAV response header to indicate that the
   collection "/home/bernard/calendars/" supports the new features
   defined in this specification.




Daboo & Douglass         Expires August 3, 2014                [Page 15]


Internet-Draft            Calendar Availability             January 2014


6.2.2.  CALDAV:free-busy-query REPORT

   A CALDAV:free-busy-query REPORT can be executed on a calendar
   collection that contains iCalendar "VAVAILABILITY" components.  When
   that is done, the server MUST aggregate the information in any
   "VAVAILABILITY" components when generating the free-busy response, as
   described in Section 5 .

6.2.3.  CALDAV:calendar-availability Property

   Name:  calendar-availability

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

   Purpose:  Defines a "VAVAILABILITY" component that will be used in
      calculating free-busy time when an iTIP free-busy request is
      targeted at the calendar user who owns the Inbox.

   Conformance:  This property MAY be protected and SHOULD NOT be
      returned by a PROPFIND DAV:allprop request.  Support for this
      property is REQUIRED.  The value of this property MUST be a valid
      iCalendar object containing "VAVAILABILITY" components and
      "VTIMEZONE" components (if required) only.

   Description:  This property allows a user to specify their
      availability by including "VAVAILABILITY" components in the value
      of this property.  If present, the server MUST use these
      "VAVAILABILITY" components when determining free-busy information
      as part of an iTIP free-busy request being handled by the server.

   Definition:

      <!ELEMENT calendar-availability (#PCDATA) >
      ; Data value MUST be iCalendar object containing
      ; "VAVAILABILITY" or "VTIMEZONE" components.

   Example:














Daboo & Douglass         Expires August 3, 2014                [Page 16]


Internet-Draft            Calendar Availability             January 2014


       <C:calendar-availability xmlns:D="DAV:"
          xmlns:C="urn:ietf:params:xml:ns:caldav"
       >BEGIN:VCALENDAR
       CALSCALE:GREGORIAN
       PRODID:-//example.com//iCalendar 2.0//EN
       VERSION:2.0
       BEGIN:VTIMEZONE
       LAST-MODIFIED:20040110T032845Z
       TZID:America/Montreal
       BEGIN:DAYLIGHT
       DTSTART:20000404T020000
       RRULE:FREQ=YEARLY;BYDAY=1SU;BYMONTH=4
       TZNAME:EDT
       TZOFFSETFROM:-0500
       TZOFFSETTO:-0400
       END:DAYLIGHT
       BEGIN:STANDARD
       DTSTART:20001026T020000
       RRULE:FREQ=YEARLY;BYDAY=-1SU;BYMONTH=10
       TZNAME:EST
       TZOFFSETFROM:-0400
       TZOFFSETTO:-0500
       END:STANDARD
       END:VTIMEZONE
       BEGIN:VAVAILABILITY
       UID:vavail-1@example.com
       DTSTAMP:20111005T133225Z
       DTSTART;TZID=America/Montreal:20111002T000000
       BEGIN:AVAILABLE
       UID:avail-1-A@example.com
       SUMMARY:Monday to Friday from 9:00 to 18:00
       DTSTART;TZID=America/Montreal:20111002T090000
       DTEND;TZID=America/Montreal:20111002T180000
       RRULE:FREQ=WEEKLY;BYDAY=MO,TU,WE,TH,FR
       END:AVAILABLE
       END:VAVAILABILITY
       END:VCALENDAR
       </C:calendar-availability>

6.2.4.  iTIP free-busy requests

   The [RFC6638] processing of an iTIP free-busy request targeted at the
   owner of the CALDAV:schedule-inbox will include free-busy information
   derived from "VAVAILABILITY" components in any calendar collection
   targeted during the request, as described in Section 5.  In addition,
   any "VAVAILABILITY" components specified in the CALDAV:calendar-
   availability property on the owner's Inbox, MUST be included in the
   free-busy calculation.



Daboo & Douglass         Expires August 3, 2014                [Page 17]


Internet-Draft            Calendar Availability             January 2014


7.  Security Considerations

   Free-busy information generated from "VAVAILABILITY" components MUST
   NOT include information other than busy or free time periods.  In
   particular, user specified property values such as "SUMMARY" and
   "DESCRIPTION" MUST NOT be copied into the free-busy result data.

   Beyond this, this specification does not add any additional security
   issues that are not already present in [RFC5545] and [RFC5546] .

8.  IANA Considerations

8.1.  Component Registrations

   This documents defines the following new iCalendar components to be
   added to the registry defined in Section 8.2.2 of [RFC5545] :

            +---------------+---------+-----------------------+
            | Component     | Status  | Reference             |
            +---------------+---------+-----------------------+
            | VAVAILABILITY | Current | RFCXXXX, Section 3.1  |
            | AVAILABLE     | Current | RFCXXXX, Section 3.1  |
            +---------------+---------+-----------------------+

8.2.  Property Registrations

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

              +----------+---------+-----------------------+
              | Property | Status  | Reference             |
              +----------+---------+-----------------------+
              | BUSYTYPE | Current | RFCXXXX, Section 3.2  |
              +----------+---------+-----------------------+

9.  Acknowledgments

   Thanks to the following for providing feedback: Toby Considine and
   Dave Thewlis.  Particular thanks go to Bernard Desruisseaux.  This
   specification came about via discussions at the Calendaring and
   Scheduling Consortium.

10.  Normative References

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





Daboo & Douglass         Expires August 3, 2014                [Page 18]


Internet-Draft            Calendar Availability             January 2014


   [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.

   [RFC6638]  Daboo, C. and B. Desruisseaux, "Scheduling Extensions to
              CalDAV", RFC 6638, June 2012.

Appendix A.  Example Calendar #1



































Daboo & Douglass         Expires August 3, 2014                [Page 19]


Internet-Draft            Calendar Availability             January 2014


   iCalendar object

       BEGIN:VCALENDAR
       CALSCALE:GREGORIAN
       PRODID:-//example.com//iCalendar 2.0//EN
       VERSION:2.0
       BEGIN:VTIMEZONE
       LAST-MODIFIED:20040110T032845Z
       TZID:America/Montreal
       BEGIN:DAYLIGHT
       DTSTART:20000404T020000
       RRULE:FREQ=YEARLY;BYDAY=1SU;BYMONTH=4
       TZNAME:EDT
       TZOFFSETFROM:-0500
       TZOFFSETTO:-0400
       END:DAYLIGHT
       BEGIN:STANDARD
       DTSTART:20001026T020000
       RRULE:FREQ=YEARLY;BYDAY=-1SU;BYMONTH=10
       TZNAME:EST
       TZOFFSETFROM:-0400
       TZOFFSETTO:-0500
       END:STANDARD
       END:VTIMEZONE
       BEGIN:VEVENT
       DTSTAMP:20111113T044111Z
       DTSTART;TZID=America/Montreal:20111106T120000
       DURATION:PT1H
       SUMMARY:Meeting
       UID:60A48841ECB90F3F215FE3D2@example.com
       END:VEVENT
       BEGIN:VAVAILABILITY
       UID:vavail-1@example.com
       DTSTAMP:20111005T133225Z
       DTSTART;TZID=America/Montreal:20111002T000000
       BEGIN:AVAILABLE
       UID:avail-1-A@example.com
       SUMMARY:Monday to Friday from 9:00 to 18:00
       DTSTART;TZID=America/Montreal:20111002T090000
       DTEND;TZID=America/Montreal:20111002T180000
       RRULE:FREQ=WEEKLY;BYDAY=MO,TU,WE,TH,FR
       END:AVAILABLE
       END:VAVAILABILITY
       END:VCALENDAR







Daboo & Douglass         Expires August 3, 2014                [Page 20]


Internet-Draft            Calendar Availability             January 2014


Appendix B.  Change History (To be removed by RFC Editor before
             publication)

   Changes in -05:

   1.  Small typos.

   2.  Fix explanation of priority.

   3.  Change uid values to make legal and easier to follow.

   Changes in -04:

   1.  Small typos.

   2.  Add prioritized example.

   Changes in -03:

   1.  Switch authors.

   2.  CalDAV scheduling is now rfc6638.

   3.  List priority as a vavailability property and define its use.

   Changes in -02:

   1.  Updated to 5545/5546 references.

   2.  Fixed some examples.

   3.  Added some more properties to the components

   4.  Fixed text that said dtstart was required in VAVAILABILITY

   Changes in -01:

   1.  Allow property on Inbox for caldav-schedule.

   2.  Clarify that DURATION can only be present in VAVAILABILITY if
       DTSTART is also present, and DTEND is not.

   3.  Updated references.

   4.  Added templates.






Daboo & Douglass         Expires August 3, 2014                [Page 21]


Internet-Draft            Calendar Availability             January 2014


Authors' Addresses

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

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


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

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































Daboo & Douglass         Expires August 3, 2014                [Page 22]


Html markup produced by rfcmarkup 1.124, available from https://tools.ietf.org/tools/rfcmarkup/