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Versions: 00 01

Network Working Group                                           C. Daboo
Internet-Draft                                                     Apple
Intended status: Standards Track                        October 28, 2011
Expires: April 30, 2012


                     Collected Extensions to CalDAV
                    draft-daboo-caldav-extensions-01

Abstract

   This document defines a set of extensions to the CalDAV calendar
   access protocol.

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
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   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 April 30, 2012.

Copyright Notice

   Copyright (c) 2011 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
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   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.






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Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  3
   2.  Conventions Used in This Document  . . . . . . . . . . . . . .  3
   3.  Extended Calendar Query Report . . . . . . . . . . . . . . . .  3
     3.1.  CALDAV:comp-filter XML Element . . . . . . . . . . . . . .  4
     3.2.  CALDAV:prop-filter XML Element . . . . . . . . . . . . . .  5
     3.3.  CALDAV:text-match XML Element  . . . . . . . . . . . . . .  5
     3.4.  Examples . . . . . . . . . . . . . . . . . . . . . . . . .  6
   4.  Advertising Supported Calendar Component Sets  . . . . . . . .  7
     4.1.  CALDAV:supported-calendar-component-sets Property  . . . .  8
   5.  Filtering by Calendar Component Type . . . . . . . . . . . . .  9
   6.  Security Considerations  . . . . . . . . . . . . . . . . . . . 10
   7.  IANA Considerations  . . . . . . . . . . . . . . . . . . . . . 10
   8.  Acknowledgments  . . . . . . . . . . . . . . . . . . . . . . . 10
   9.  References . . . . . . . . . . . . . . . . . . . . . . . . . . 11
     9.1.  Normative References . . . . . . . . . . . . . . . . . . . 11
     9.2.  Informative References . . . . . . . . . . . . . . . . . . 11
   Appendix A.  Change History (To be removed by RFC Editor
                before publication) . . . . . . . . . . . . . . . . . 11
   Author's Address . . . . . . . . . . . . . . . . . . . . . . . . . 12






























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1.  Introduction

   [RFC4791] defines the CalDAV Calendar Access protocol for accessing
   calendar data stored on a server.  With the popularity of CalDAV
   increasing, a number of useful extensions have been proposed to
   improve the protocol.  This specification collects several of those
   extensions into one document for convenience.  Each extension defined
   in this specification can be implemented independently of any of the
   others.

   Discussion of this Internet-Draft is taking place on the mailing list
   <https://www.ietf.org/mailman/listinfo/caldav>.


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].

   Other notations used in this memo follow the notations of [RFC4791].


3.  Extended Calendar Query Report

   The CALDAV:calendar-query report defined in Section 7.8 of [RFC4791]
   allows a client to search calendar data for a match to iCalendar
   component, property or parameter details.  As defined, this option
   supports querying multiple attributes of the iCalendar data at
   various "nesting" levels based on the syntactic structure of
   iCalendar itself.  When multiple attributes are queried at the same
   level, each has to match for the query to be successful - effectively
   defining a logical "and" operation.  This does not allow clients to
   execute a single query to match different attributes of different
   component types (e.g., clients cannot search for VEVENTs with a
   particular time-range, or VTODOs that are not completed).  Since
   there is a need to be able to execute such queries, a logical "or"
   operation is needed.

   This specification adds a "test" XML attribute to the CALDAV:comp-
   filter and CALDAV:prop-filter XML elements that accepts values of
   "allof" or "anyof" to indicate logical "and" or "or" operations
   respectively.  This copies the behavior defined for CARDDAV:
   addressbook-query reports defined in Section 10.5 of [RFC6352], with
   the exception that the default value for the attribute is "allof" to
   match the current behavior.




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   The text comparison operation in [RFC4791] is a simple "contains"
   operation, however more sophisticated comparisons are sometimes
   needed (e.g., 'starts with', 'equals', etc).

   This specification adds a "match-type" XML attribute to the CALDAV:
   text-match XML element that accepts values of "equals", "contains",
   "starts-with", or "ends-with", to indicate the comparison operation
   to be used.  This copies the behavior defined for CARDDAV:
   addressbook-query reports defined in Section 10.5.4 of [RFC6352].

   Sometimes clients want to search all component types for a match
   (e.g., clients cannot find all calendar object resources that contain
   a SUMMARY property value matching some text irrespective of the top-
   level component type).

   This specification allows the use of a single "*" character in the
   "name" attribute of "comp-filter" elements to require the server to
   match any component type.

   Servers advertise support for this extension by including the token
   "calendar-query-extended" in the DAV response header to an OPTIONS
   request on any resource supporting the extended query report.
   Clients MUST check for the presence of that token before using the
   "test" or "match-type" XML attributes.

   This specification extends the [RFC4791] XML syntax for the CALDAV:
   comp-filter, CALDAV:prop-filter and CALDAV:text-match XML elements as
   follows.

3.1.  CALDAV:comp-filter XML Element

   XML Element:  CALDAV:comp-filter

   Updated Definition:

   <!ELEMENT comp-filter (is-not-defined | (time-range?,
                          prop-filter*, comp-filter*))>

   <!ATTLIST comp-filter name CDATA #REQUIRED
                         test (allof | anyof) "allof">
   <!-- name value:
           a calendar object or calendar component type (e.g., VEVENT),
           or the value "*" to indicate a match against any type

        test value:
           allof logical AND for matches
           anyof logical OR for matches
    -->



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   Additional Description:  The "test" attribute specifies whether any
      (logical OR) or all (logical AND) of the is-not-defined, time-
      range, comp-filter or param-filter tests need to match in order
      for the overall filter to match.

3.2.  CALDAV:prop-filter XML Element

   XML Element:  CALDAV:prop-filter

   Updated Definition:

   <!ELEMENT prop-filter (is-not-defined |
                          ((time-range | text-match)?,
                           param-filter*))>

   <!ATTLIST prop-filter name CDATA #REQUIRED
                         test (allof | anyof) "allof">
   <!-- name value:
           a calendar property name (e.g., ATTENDEE)

        test value:
           allof logical AND for matches
           anyof logical OR for matches
    -->

   Additional Description:  The "test" attribute specifies whether any
      (logical OR) or all (logical AND) of the is-not-defined, time-
      range, text-filter or param-filter tests need to match in order
      for the overall filter to match.

3.3.  CALDAV:text-match XML Element

   XML Element:  CALDAV:text-match

   Updated Definition:

   <!ELEMENT text-match (#PCDATA)>
   <!-- PCDATA value: string -->

   <!ATTLIST text-match
       collation        CDATA "i;ascii-casemap"
       negate-condition (yes | no) "no"
       match-type (equals|contains|starts-with|ends-with) "contains">

   Additional Description:  The "match-type" attribute is used to
      indicate the type of match operation to use.  Possible choices
      are:




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         "equals" - an exact match to the target string

         "contains" - a substring match, matching anywhere within the
         target string

         "starts-with" - a substring match, matching only at the start
         of the target string

         "ends-with" - a substring match, matching only at the end of
         the target string

3.4.  Examples

   In this request, the client is querying for VEVENTs that start on or
   after a specific date, or VTODOs that are not completed and not
   cancelled.

   REPORT /bernard/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/>
     </D:prop>
     <C:filter>
       <C:comp-filter name="VCALENDAR" test="anyof">
         <C:comp-filter name="VEVENT">
           <C:time-range start="20110101T000000Z"/>
         </C:comp-filter>
         <C:comp-filter name="VTODO" test="allof">
           <C:prop-filter name="COMPLETED">
             <C:is-not-defined/>
           </C:prop-filter>
           <C:prop-filter name="STATUS">
             <C:text-match
                negate-condition="yes"
                match-type="equals">CANCELLED</C:text-match>
           </C:prop-filter>
         </C:comp-filter>
       </C:comp-filter>
     </C:filter>
   </C:calendar-query>




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   In this request, the client is querying for any component that
   contains a VALARM sub-component.

   REPORT /bernard/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/>
     </D:prop>
     <C:filter>
       <C:comp-filter name="VCALENDAR">
         <C:comp-filter name="*">
           <C:comp-filter name="VALARM" />
         </C:comp-filter>
       </C:comp-filter>
     </C:filter>
   </C:calendar-query>


4.  Advertising Supported Calendar Component Sets

   CalDAV [RFC4791] supports the notion of calendar collections that are
   restricted to only containing components of a certain type, or set of
   types.  The protocol allows clients to specify the restricted
   component sets by supplying a CALDAV:supported-calendar-component-set
   WebDAV property in an MKCALENDAR or extended MKCOL [RFC5689] request
   that creates a calendar collection.  However, servers themselves
   might need to restrict the allowed sets of components that can be
   used in any one calendar (e.g., some servers might only support
   calendar collections containing components of one type).  Currently
   there is no way for a client to determine what the allowed
   combination of component types is for use with MKCALENDAR or extended
   MKCOL.

   This specification adds a new CALDAV:supported-calendar-component-
   sets WebDAV property for use on calendar home collections.  This
   property enumerates the allowed sets of calendar components that the
   server will support for use with MKCALENDAR or extended MKCOL
   requests.  Clients SHOULD check for the presence of this property
   before issuing an MKCALENDAR or extended MKCOL request that includes
   a CALDAV:supported-calendar-component-set WebDAV property.  When the
   new property is found on a calendar home, clients MUST only use a



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   CALDAV:supported-calendar-component-set is one advertised as being
   supported.

4.1.  CALDAV:supported-calendar-component-sets Property

   Name:  supported-calendar-component-sets

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

   Purpose:  Enumerates the sets of component restrictions the server is
      willing to allow the client to specify in MKCALENDAR or extended
      MKCOL requests.

   Protected:  This property MUST be protected and SHOULD NOT be
      returned by a PROPFIND allprop request (as defined in Section 14.2
      of [RFC4918]).

   COPY/MOVE behavior:  This property value MUST be preserved in COPY
      and MOVE operations.

   Description:  If servers apply restrictions on the allowed calendar
      component sets used when creating a calendar, then those servers
      SHOULD advertise this property on each calendar home collection
      within which the restrictions apply.  In the absence of this
      property, clients cannot assume anything about whether the server
      will enforce a set of restrictions or not - in that case clients
      need to handle the server rejecting certain combinations of
      restricted component sets.  If this property is present, but
      contains no child XML elements, then clients can assume that the
      server imposes no restrictions on the combinations of component
      types it is willing to accept.  If present, each CALDAV:supported-
      calendar-component-set element represents a valid restriction the
      client can use in an MKCALENDAR or extended MKCOL request when
      creating a calendar.

   Definition:

      <!ELEMENT supported-calendar-component-sets
                (supported-calendar-component-set*) >
      <!-- supported-calendar-component-set defined in RFC4791 -->

   Example:









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

     <!-- Calendars with any standard iCalendar component -->
     <C:supported-calendar-component-set>
       <C:comp name="VEVENT" />
       <C:comp name="VFREEBUSY" />
       <C:comp name="VJOURNAL" />
       <C:comp name="VTODO" />
     </C:supported-calendar-component-set>

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

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

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


5.  Filtering by Calendar Component Type

   Calendar clients are sometimes "scoped" to only utilize one type of
   main calendar component type (e.g., a scheduling client that only
   handles "VEVENT" components, or a task manager that only handles
   "VTODO" components).  CalDAV provides a calendar query report that
   allows clients to find only calendar object resources that contain a
   specified main component type, which is useful when initially loading
   the contents of a calendar into a local cache.  However, clients also
   need to keep that cache updated as changes occur on the server.  One
   way to do that is to use the WebDAV sync report
   [I-D.daboo-webdav-sync], but that report will return changes for all
   calendar object resources within a calendar collection.  Thus
   "scoped" clients will be forced to load calendar object resources
   containing component types they do not care about to discover what
   type they are, or issue additional queries to see whether the changes
   reported by the sync report are for component types it handles.  A
   better approach would be to have a way for the WebDAV sync report
   response to include details of the calendar component type for each



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   calendar object resource that it reports as changed.

   To better "scope" a WebDAV sync report, this specification recommends
   that servers SHOULD always include a "component=" parameter (as
   defined in Section 8.1 of [RFC5545]) in the DAV:getcontenttype WebDAV
   property media-type value reported for calendar object resources.
   Clients can then request that property be returned in the WebDAV sync
   report response for each resource, and thus quickly determine which
   changes are relevant to them based on component type.

   Example partial WebDAV sync report response with a component type
   included.

   <D:response>
     <D:href
   >http://calendar.example.com/cyrusdaboo/calendar.ics</D:href>
     <D:propstat>
       <D:prop>
         <D:getetag>"00003-abcd1"</D:getetag>
         <D:getcontenttype
         >text/calendar;charset=utf-8;component=vevent<
         /D:getcontenttype>
       </D:prop>
       <D:status>HTTP/1.1 200 OK</D:status>
     </D:propstat>
    </D:response>


6.  Security Considerations

   This specification does not introduce any new security concerns
   beyond those addressed in CalDAV [RFC4791] and iCalendar [RFC5545].


7.  IANA Considerations

   No IANA actions are needed.


8.  Acknowledgments

   Thanks to Bernard Desruisseaux, Mike Douglass, Jeffrey Harris, Arnaud
   Quillaud, and Nick Zitzmann.  This specification came about via
   discussions at the Calendaring and Scheduling Consortium.


9.  References




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9.1.  Normative References

   [I-D.daboo-webdav-sync]
              Daboo, C. and A. Quillaud, "Collection Synchronization for
              WebDAV", draft-daboo-webdav-sync-06 (work in progress),
              July 2011.

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

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

   [RFC4918]  Dusseault, L., "HTTP Extensions for Web Distributed
              Authoring and Versioning (WebDAV)", RFC 4918, June 2007.

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

   [RFC5689]  Daboo, C., "Extended MKCOL for Web Distributed Authoring
              and Versioning (WebDAV)", RFC 5689, September 2009.

9.2.  Informative References

   [RFC6352]  Daboo, C., "CardDAV: vCard Extensions to Web Distributed
              Authoring and Versioning (WebDAV)", RFC 6352, August 2011.


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

   Changes in -01:

   1.  Changed description of COPY/MOVE for supported-calendar-
       component-sets property

   2.  Removed bogus text in property description.

   3.  Changed supported-calendar-component-sets to use supported-
       calendar-component-set as a child element.

   4.  Added recommendation to use "component=" parameter in DAV:
       getcontenttype WebDAV properties on calendar object resources.






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Author's Address

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

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









































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