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

Network Working Group                                           C. Daboo
Internet-Draft                                            Apple Computer
Intended status: Standards Track                         B. Desruisseaux
Expires: May 18, 2007                                             Oracle
                                                       November 14, 2006


                         Calendar Availability
                  draft-daboo-calendar-availability-00

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Copyright Notice

   Copyright (C) The Internet Society (2006).

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.




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   This document also defines extensions to CalDAV calendar-access and
   calendar-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.


Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  3
   2.  Conventions Used in This Document  . . . . . . . . . . . . . .  3
   3.  iCalendar Extensions . . . . . . . . . . . . . . . . . . . . .  4
     3.1.  Availability Component . . . . . . . . . . . . . . . . . .  4
     3.2.  Busy Time Type . . . . . . . . . . . . . . . . . . . . . .  8
   4.  Calculating Free-Busy Time . . . . . . . . . . . . . . . . . .  9
     4.1.  Examples . . . . . . . . . . . . . . . . . . . . . . . . . 10
   5.  CalDAV Extensions  . . . . . . . . . . . . . . . . . . . . . . 11
     5.1.  CalDAV Requirements Overview . . . . . . . . . . . . . . . 11
     5.2.  New features in CalDAV . . . . . . . . . . . . . . . . . . 12
   6.  Security Considerations  . . . . . . . . . . . . . . . . . . . 13
   7.  IANA Considerations  . . . . . . . . . . . . . . . . . . . . . 13
   8.  Acknowledgments  . . . . . . . . . . . . . . . . . . . . . . . 13
   9.  Normative References . . . . . . . . . . . . . . . . . . . . . 13
   Appendix A.  Example Calendar #1 . . . . . . . . . . . . . . . . . 14
   Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 16
   Intellectual Property and Copyright Statements . . . . . . . . . . 17






















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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 her 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
   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 for
   different periods of available time to appear for different users.

   However, iCalendar [RFC2445] does not provide a way to specify a
   repeating period of available or unavailable time as "VFREEBUSY"
   components cannot include any form of recurrence information, as
   opposed to "VEVENT" components which can.  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 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 [I-D.dusseault-caldav]
   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-schedule
   [I-D.desruisseaux-caldav-sched] 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-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].




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   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.


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.  Availability 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 / created / dtstart / last-mod /
                            organizer / seq / summary / url /

                            ; either 'dtend' or 'duration' may appear
                            ; in a 'availabilityprop', but 'dtend' and



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                            ; 'duration' MUST NOT occur in the same
                            ; 'availabilityprop'

                            dtend / duration /

                            ; the following are OPTIONAL,
                            ; and MAY occur more than once

                            categories / comment / contact / x-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 a 'dtend' or a 'duration' is required
                         ; in a 'availableprop', but 'dtend' and
                         ; 'duration' MUST NOT occur in the same
                         ; 'availableprop', and each MUST NOT occur more
                         ; than once

                         dtend / duration /

                         ; the following are OPTIONAL,
                         ; but MUST NOT occur more than once

                         created / last-mod / recurid / rrule /
                         summary /

                         ; the following are OPTIONAL,
                         ; and MAY occur more than once

                         categories / comment / contact / exdate /
                         rdate / x-prop

                         )







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   Description:  A "VAVAILABILITY" component indicates a period of time
      within which availability information is provided.  A
      "VAVAILABILITY" component MUST specify a start time and optionally
      an end time or duration.  Within that time period, availability
      defaults to a free-busy type of "BUSY", except for any time
      periods corresponding to "AVAILABLE" sub-components.

      "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 "TZID"
      parameter value.

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

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

        BEGIN:VAVAILABILITY
        ORGANIZER:mailto:bernard@example.com
        UID:20061005T133225Z-00001@example.com
        DTSTAMP:20061005T133225Z
        DTSTART;TZID=America/Montreal:20061002T000000
        BEGIN:AVAILABLE
        UID:20061005T133225Z-00001-A@example.com
        SUMMARY:Monday to Friday from 9:00 to 17:00
        DTSTART;TZID=America/Montreal:20061002T090000
        DTEND;TZID=America/Montreal:20061002T170000
        RRULE:FREQ=WEEKLY;BYDAY=MO,TU,WE,TH,FR
        END:AVAILABLE
        END:VAVAILABILITY



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      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, and Friday 9:00 AM to
      12:00 PM in the America/Montreal time zone:

        BEGIN:VAVAILABILITY
        ORGANIZER:mailto:bernard@example.com
        UID:20061005T133225Z-00001@example.com
        DTSTAMP:20061005T133225Z
        DTSTART;TZID=America/Montreal:20061002T000000
        DTEND;TZID=America/Montreal:20061202T000000
        BEGIN:AVAILABLE
        UID:20061005T133225Z-00001-A@example.com
        SUMMARY:Monday to Thursday from 9:00 to 17:00
        DTSTART;TZID=America/Montreal:20061002T090000
        DTEND;TZID=America/Montreal:20061002T170000
        RRULE:FREQ=WEEKLY;BYDAY=MO,TU,WE,TH
        END:AVAILABLE
        BEGIN:AVAILABLE
        UID:20061005T133225Z-00001-B@example.com
        SUMMARY:Friday from 9:00 to 12:00
        DTSTART;TZID=America/Montreal:20061006T090000
        DTEND;TZID=America/Montreal:20061006T120000
        RRULE:FREQ=WEEKLY;BYDAY=FR
        END:AVAILABLE
        END:VAVAILABILITY

      The following is an example of three "VAVAILABILITY" calendar
      components used to represent the availability of an itinerant
      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
      each overall period is covered by separate "VAVAILABILITY"
      components.  The last of these has no DTEND so continues on "for
      ever".  This example shows how "exceptions" to available time can
      be handled.















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        BEGIN:VAVAILABILITY
        ORGANIZER:mailto:bernard@example.com
        UID:20061005T133225Z-00001@example.com
        DTSTAMP:20061005T133225Z
        DTSTART;TZID=America/Montreal:20061002T000000
        DTEND;TZID=America/Montreal:20061023T030000
        BEGIN:AVAILABLE
        UID:20061005T133225Z-00001-A@example.com
        SUMMARY:Monday to Friday from 9:00 to 17:00
        DTSTART;TZID=America/Montreal:20061002T090000
        DTEND;TZID=America/Montreal:20061002T170000
        RRULE:FREQ=WEEKLY;BYDAY=MO,TU,WE,TH,FR
        END:AVAILABLE
        END:VAVAILABILITY
        BEGIN:VAVAILABILITY
        ORGANIZER:mailto:bernard@example.com
        UID:20061005T133225Z-00001@example.com
        DTSTAMP:20061005T133225Z
        DTSTART;TZID=America/Los_Angeles:20061023T000000
        DTEND;TZID=America/Los_Angeles:20061030T000000
        BEGIN:AVAILABLE
        UID:20061005T133225Z-00001-A@example.com
        SUMMARY:Monday to Friday from 9:00 to 17:00
        DTSTART;TZID=America/Los_Angeles:20061023T090000
        DTEND;TZID=America/Los_Angeles:20061023T170000
        RRULE:FREQ=WEEKLY;BYDAY=MO,TU,WE,TH,FR
        END:AVAILABLE
        END:VAVAILABILITY
        BEGIN:VAVAILABILITY
        ORGANIZER:mailto:bernard@example.com
        UID:20061005T133225Z-00001@example.com
        DTSTAMP:20061005T133225Z
        DTSTART;TZID=America/Montreal:20061030T030000
        BEGIN:AVAILABLE
        UID:20061005T133225Z-00001-A@example.com
        SUMMARY:Monday to Friday from 9:00 to 17:00
        DTSTART;TZID=America/Montreal:20061030T090000
        DTEND;TZID=America/Montreal:20061030T170000
        RRULE:FREQ=WEEKLY;BYDAY=MO,TU,WE,TH,FR
        END:AVAILABLE
        END:VAVAILABILITY

3.2.  Busy Time Type








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   Property Name:  BUSYTYPE

   Purpose:  This property specifies the default busy time type.

   Value Type:  TEXT

   Property Parameters:  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 = *(";" xparam)

        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.  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.  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 "VFREEBUSY" [RFC2446] request or
   through some other mechanism (e.g., a CalDAV calendar-access CALDAV:
   free-busy-query REPORT).

   When a "VAVAILABILITY" component is present and intersects the time-
   range for the free-busy request, the time covered by the



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   "VAVAILABILITY" component is set to busy and then portions of it
   "carved out" to be free based on the "AVAILABLE" components in the
   "VAVAILABILITY" component.  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:

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

   2.  For each "VAVAILABILITY" component:

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

       2.  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:

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

           1.  Expand all recurring instances, taking into account
               overridden instances, ignoring those not within the free-
               busy request time-range.

           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.

4.1.  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:



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     +-----------+--------------------------------------------------+
     | 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.   |
     +-----------+--------------------------------------------------+

4.1.1.  Simple Example

   A free-busy request for Monday, 6th November 2006, 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  |
   +------+----+----+----+----+----+----+----+----+----+----+----+----+

4.1.2.  TBD

   More examples here../not sure what though.


5.  CalDAV Extensions

5.1.  CalDAV Requirements Overview

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

   o  MUST support CalDAV calendar-access;

   o  MAY support CalDAV calendar-schedule;

   o  MUST support "VAVAILABILITY" components in a calendar collection
      resource;





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

   o  MUST support CalDAV calendar-schedule iTIP [RFC2446] free busy
      requests that aggregate the information in any "VAVAILABILITY"
      components, if the CalDAV calendar-schedule feature is available.

5.2.  New features in CalDAV

5.2.1.  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.

5.2.1.1.  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.

5.2.2.  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



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   described in Section 4.

5.2.3.  iTIP VFREEBUSY requests

   The [I-D.desruisseaux-caldav-sched] processing of a "VFREEBUSY"
   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 4.


6.  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 [RFC2445] and [RFC2446].


7.  IANA Considerations

   TBD - register new components using 2445bis templates.


8.  Acknowledgments

   This specification came about via discussions at the Calendaring and
   Scheduling Consortium.


9.  Normative References

   [I-D.desruisseaux-caldav-sched]
              Daboo, C., Desruisseaux, B., and L. Dusseault, "Scheduling
              Extensions to CalDAV", draft-desruisseaux-caldav-sched-02
              (work in progress), June 2006.

   [I-D.dusseault-caldav]
              Daboo, C., Desruisseaux, B., and L. Dusseault,
              "Calendaring Extensions to WebDAV (CalDAV)",
              draft-dusseault-caldav-15 (work in progress),
              September 2006.

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



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   [RFC2445]  Dawson, F. and D. Stenerson, "Internet Calendaring and
              Scheduling Core Object Specification (iCalendar)",
              RFC 2445, November 1998.

   [RFC2446]  Silverberg, S., Mansour, S., Dawson, F., and R. Hopson,
              "iCalendar Transport-Independent Interoperability Protocol
              (iTIP) Scheduling Events, BusyTime, To-dos and Journal
              Entries", RFC 2446, November 1998.


Appendix A.  Example Calendar #1








































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   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:20061113T044111Z
       DTSTART;TZID=America/Montreal:20061106T120000
       DURATION:PT1H
       SUMMARY:Meeting
       UID:60A48841ECB90F3F215FE3D2@example.com
       END:VEVENT
       BEGIN:VAVAILABILITY
       UID:20061005T133225Z-00001@example.com
       DTSTAMP:20061005T133225Z
       DTSTART;TZID=America/Montreal:20061002T000000
       BEGIN:AVAILABLE
       UID:20061005T133225Z-00001-A@example.com
       SUMMARY:Monday to Friday from 9:00 to 18:00
       DTSTART;TZID=America/Montreal:20061002T090000
       DTEND;TZID=America/Montreal:20061002T180000
       RRULE:FREQ=WEEKLY;BYDAY=MO,TU,WE,TH,FR
       END:AVAILABLE
       END:VAVAILABILITY
       END:VCALENDAR







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Internet-Draft            Calendar Availability            November 2006


Authors' Addresses

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

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


   Bernard Desruisseaux
   Oracle Corporation
   600 blvd. de Maisonneuve West
   Suite 1900
   Montreal, QC  H3A 3J2
   CA

   Email: bernard.desruisseaux@oracle.com
   URI:   http://www.oracle.com/






























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Internet-Draft            Calendar Availability            November 2006


Full Copyright Statement

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