Internet DRAFT - draft-dusseault-caldav

draft-dusseault-caldav






Network Working Group                                           C. Daboo
Internet-Draft                                            Apple Computer
Expires: March 17, 2007                                  B. Desruisseaux
                                                                  Oracle
                                                            L. Dusseault
                                                                    OSAF
                                                      September 13, 2006


               Calendaring Extensions to WebDAV (CalDAV)
                       draft-dusseault-caldav-15

Status of this Memo

   By submitting this Internet-Draft, each author represents that any
   applicable patent or other IPR claims of which he or she is aware
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   This Internet-Draft will expire on March 17, 2007.

Copyright Notice

   Copyright (C) The Internet Society (2006).

Abstract

   This document specifies a set of methods, headers, message bodies,
   properties, and reports that define calendar access extensions to the
   WebDAV protocol.  The new protocol elements are intended to make
   WebDAV-based calendaring and scheduling an interoperable standard
   that supports calendar access, calendar management, calendar sharing,



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   and calendar publishing.


Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   5
     1.1.  Notational Conventions  . . . . . . . . . . . . . . . . .   5
     1.2.  XML Namespaces and Processing . . . . . . . . . . . . . .   5
     1.3.  Method Preconditions and Postconditions . . . . . . . . .   6
   2.  Requirements Overview . . . . . . . . . . . . . . . . . . . .   6
   3.  Calendaring Data Model  . . . . . . . . . . . . . . . . . . .   7
     3.1.  Calendar Server . . . . . . . . . . . . . . . . . . . . .   7
     3.2.  Recurrence and the Data Model . . . . . . . . . . . . . .   8
   4.  Calendar Resources  . . . . . . . . . . . . . . . . . . . . .   9
     4.1.  Calendar Object Resources . . . . . . . . . . . . . . . .   9
     4.2.  Calendar Collection . . . . . . . . . . . . . . . . . . .  10
   5.  Calendar Access Feature . . . . . . . . . . . . . . . . . . .  11
     5.1.  Calendar Access Support . . . . . . . . . . . . . . . . .  11
       5.1.1.  Example: Using OPTIONS for the Discovery of
               Calendar Access Support . . . . . . . . . . . . . . .  12
     5.2.  Calendar Collection Properties  . . . . . . . . . . . . .  12
       5.2.1.  CALDAV:calendar-description Property  . . . . . . . .  12
       5.2.2.  CALDAV:calendar-timezone Property . . . . . . . . . .  13
       5.2.3.  CALDAV:supported-calendar-component-set Property  . .  14
       5.2.4.  CALDAV:supported-calendar-data Property . . . . . . .  15
       5.2.5.  CALDAV:max-resource-size Property . . . . . . . . . .  16
       5.2.6.  CALDAV:min-date-time Property . . . . . . . . . . . .  17
       5.2.7.  CALDAV:max-date-time Property . . . . . . . . . . . .  18
       5.2.8.  CALDAV:max-instances Property . . . . . . . . . . . .  18
       5.2.9.  CALDAV:max-attendees-per-instance Property  . . . . .  19
       5.2.10. Additional Precondition for PROPPATCH . . . . . . . .  20
     5.3.  Creating Resources  . . . . . . . . . . . . . . . . . . .  20
       5.3.1.  MKCALENDAR Method . . . . . . . . . . . . . . . . . .  20
         5.3.1.1.  Status Codes  . . . . . . . . . . . . . . . . . .  22
         5.3.1.2.  Example: Successful MKCALENDAR request  . . . . .  23
       5.3.2.  Creating Calendar Object Resources  . . . . . . . . .  25
         5.3.2.1.  Additional Preconditions for PUT, COPY and MOVE .  26
       5.3.3.  Non-standard components, properties and parameters  .  28
       5.3.4.  Calendar Object Resource Entity Tag . . . . . . . . .  28
   6.  Calendaring Access Control  . . . . . . . . . . . . . . . . .  29
     6.1.  Calendaring Privilege . . . . . . . . . . . . . . . . . .  29
       6.1.1.  CALDAV:read-free-busy Privilege . . . . . . . . . . .  29
     6.2.  Additional Principal Property . . . . . . . . . . . . . .  30
       6.2.1.  CALDAV:calendar-home-set Property . . . . . . . . . .  30
   7.  Calendaring Reports . . . . . . . . . . . . . . . . . . . . .  31
     7.1.  REPORT Method . . . . . . . . . . . . . . . . . . . . . .  31
     7.2.  Ordinary collections  . . . . . . . . . . . . . . . . . .  31
     7.3.  Date and floating time  . . . . . . . . . . . . . . . . .  32



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     7.4.  Time range filtering  . . . . . . . . . . . . . . . . . .  32
     7.5.  Searching Text: Collations  . . . . . . . . . . . . . . .  33
       7.5.1.  CALDAV:supported-collation-set Property . . . . . . .  34
     7.6.  Partial Retrieval . . . . . . . . . . . . . . . . . . . .  34
     7.7.  Non-standard components, properties and parameters  . . .  35
     7.8.  CALDAV:calendar-query Report  . . . . . . . . . . . . . .  35
       7.8.1.  Example: Partial retrieval of events by time range  .  38
       7.8.2.  Example: Partial retrieval of recurring events  . . .  42
       7.8.3.  Example: Expanded retrieval of recurring events . . .  45
       7.8.4.  Example: Partial retrieval of stored free busy
               components  . . . . . . . . . . . . . . . . . . . . .  47
       7.8.5.  Example: Retrieval of to-dos by alarm time range  . .  49
       7.8.6.  Example: Retrieval of event by UID  . . . . . . . . .  51
       7.8.7.  Example: Retrieval of events by PARTSTAT  . . . . . .  53
       7.8.8.  Example: Retrieval of events only . . . . . . . . . .  55
       7.8.9.  Example: Retrieval of all pending to-dos  . . . . . .  59
       7.8.10. Example: Attempt to query unsupported property  . . .  62
     7.9.  CALDAV:calendar-multiget Report . . . . . . . . . . . . .  63
       7.9.1.  Example: Successful CALDAV:calendar-multiget Report .  64
     7.10. CALDAV:free-busy-query Report . . . . . . . . . . . . . .  66
       7.10.1. Example: Successful CALDAV:free-busy-query Report . .  68
   8.  Guidelines  . . . . . . . . . . . . . . . . . . . . . . . . .  68
     8.1.  Client-to-client Interoperability . . . . . . . . . . . .  69
     8.2.  Synchronization Operations  . . . . . . . . . . . . . . .  69
       8.2.1.  Use of Reports  . . . . . . . . . . . . . . . . . . .  69
         8.2.1.1.  Restrict the Time Range . . . . . . . . . . . . .  69
         8.2.1.2.  Synchronize by Time Range . . . . . . . . . . . .  69
         8.2.1.3.  Synchronization Process . . . . . . . . . . . . .  70
       8.2.2.  Restrict the Properties Returned  . . . . . . . . . .  72
     8.3.  Use of Locking  . . . . . . . . . . . . . . . . . . . . .  72
     8.4.  Finding calendars . . . . . . . . . . . . . . . . . . . .  72
     8.5.  Storing and Using Attachments . . . . . . . . . . . . . .  74
       8.5.1.  Inline attachments  . . . . . . . . . . . . . . . . .  74
       8.5.2.  External attachments  . . . . . . . . . . . . . . . .  75
     8.6.  Storing and Using Alarms  . . . . . . . . . . . . . . . .  76
   9.  XML Element Definitions . . . . . . . . . . . . . . . . . . .  77
     9.1.  CALDAV:calendar XML Element . . . . . . . . . . . . . . .  77
     9.2.  CALDAV:mkcalendar XML Element . . . . . . . . . . . . . .  77
     9.3.  CALDAV:mkcalendar-response XML Element  . . . . . . . . .  77
     9.4.  CALDAV:supported-collation XML Element  . . . . . . . . .  78
     9.5.  CALDAV:calendar-query XML Element . . . . . . . . . . . .  78
     9.6.  CALDAV:calendar-data XML Element  . . . . . . . . . . . .  79
       9.6.1.  CALDAV:comp XML Element . . . . . . . . . . . . . . .  80
       9.6.2.  CALDAV:allcomp XML Element  . . . . . . . . . . . . .  80
       9.6.3.  CALDAV:allprop XML Element  . . . . . . . . . . . . .  81
       9.6.4.  CALDAV:prop XML Element . . . . . . . . . . . . . . .  81
       9.6.5.  CALDAV:expand XML Element . . . . . . . . . . . . . .  82
       9.6.6.  CALDAV:limit-recurrence-set XML Element . . . . . . .  83



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       9.6.7.  CALDAV:limit-freebusy-set XML Element . . . . . . . .  84
     9.7.  CALDAV:filter XML Element . . . . . . . . . . . . . . . .  84
       9.7.1.  CALDAV:comp-filter XML Element  . . . . . . . . . . .  85
       9.7.2.  CALDAV:prop-filter XML Element  . . . . . . . . . . .  85
       9.7.3.  CALDAV:param-filter XML Element . . . . . . . . . . .  86
       9.7.4.  CALDAV:is-not-defined XML Element . . . . . . . . . .  87
       9.7.5.  CALDAV:text-match XML Element . . . . . . . . . . . .  87
     9.8.  CALDAV:timezone XML Element . . . . . . . . . . . . . . .  88
     9.9.  CALDAV:time-range XML Element . . . . . . . . . . . . . .  88
     9.10. CALDAV:calendar-multiget XML Element  . . . . . . . . . .  93
     9.11. CALDAV:free-busy-query XML Element  . . . . . . . . . . .  94
   10. Internationalization Considerations . . . . . . . . . . . . .  94
   11. Security Considerations . . . . . . . . . . . . . . . . . . .  94
   12. IANA Consideration  . . . . . . . . . . . . . . . . . . . . .  95
     12.1. Namespace Registration  . . . . . . . . . . . . . . . . .  95
   13. Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .  96
   14. References  . . . . . . . . . . . . . . . . . . . . . . . . .  96
     14.1. Normative References  . . . . . . . . . . . . . . . . . .  96
     14.2. Informative References  . . . . . . . . . . . . . . . . .  97
   Appendix A.  CalDAV Method Privilege Table (Normative)  . . . . .  97
   Appendix B.  Calendar collections used in the examples  . . . . .  98
   Appendix C.  Changes (to be removed prior to publication as an
                RFC) . . . . . . . . . . . . . . . . . . . . . . . . 104
     C.1.  Changes in -15  . . . . . . . . . . . . . . . . . . . . . 104
     C.2.  Changes in -14  . . . . . . . . . . . . . . . . . . . . . 105
     C.3.  Changes in -13  . . . . . . . . . . . . . . . . . . . . . 105
     C.4.  Changes in -12  . . . . . . . . . . . . . . . . . . . . . 106
     C.5.  Changes in -11  . . . . . . . . . . . . . . . . . . . . . 106
     C.6.  Changes in -10  . . . . . . . . . . . . . . . . . . . . . 107
     C.7.  Changes in -09  . . . . . . . . . . . . . . . . . . . . . 108
     C.8.  Changes in -08  . . . . . . . . . . . . . . . . . . . . . 109
     C.9.  Changes in -07  . . . . . . . . . . . . . . . . . . . . . 110
     C.10. Changes in -06  . . . . . . . . . . . . . . . . . . . . . 111
     C.11. Changes in -05  . . . . . . . . . . . . . . . . . . . . . 111
     C.12. Changes in -04  . . . . . . . . . . . . . . . . . . . . . 112
     C.13. Changes in -03  . . . . . . . . . . . . . . . . . . . . . 113
     C.14. Changes in -02  . . . . . . . . . . . . . . . . . . . . . 113
     C.15. Changes in -01  . . . . . . . . . . . . . . . . . . . . . 113
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . . 114
   Intellectual Property and Copyright Statements  . . . . . . . . . 115











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1.  Introduction

   The concept of using HTTP [RFC2616] and WebDAV [RFC2518] as a basis
   for a calendar access protocol is by no means a new concept: it was
   discussed in the IETF CALSCH working group as early as 1997 or 1998.
   Several companies have implemented calendar access protocols using
   HTTP to upload and download iCalendar [RFC2445] objects, and using
   WebDAV to get listings of resources.  However, those implementations
   do not interoperate because there are many small and big decisions to
   be made in how to model calendaring data as WebDAV resources, as well
   as how to implement required features that aren't already part of
   WebDAV.  This document proposes a way to model calendar data in
   WebDAV, with additional features to make an interoperable calendar
   access protocol.

1.1.  Notational Conventions

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

   The term "protected" is used in the Conformance field of property
   definitions as defined in Section 1.4.2 of [RFC3253].

   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.

1.2.  XML Namespaces and Processing

   Definitions of XML elements in this document use XML element type
   declarations (as found in XML Document Type Declarations), described
   in Section 3.2 of [W3C.REC-xml-20060816].

   The namespace "urn:ietf:params:xml:ns:caldav" is reserved for the XML
   elements defined in this specification, its revisions, and related
   CalDAV specifications.  XML elements defined by individual
   implementations MUST NOT use the "urn:ietf:params:xml:ns:caldav"
   namespace, and instead should use a namespace that they control.

   The XML declarations used in this document do not include namespace
   information.  Thus, implementers must not use these declarations as
   the only way to create valid CalDAV properties or to validate CalDAV
   XML element type.  Some of the declarations refer to XML elements
   defined by WebDAV [RFC2518] which use the "DAV:" namespace.  Wherever
   such XML elements appear, they are explicitly prefixed with "DAV:" to
   avoid confusion.



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   Also note that some CalDAV XML element names are identical to WebDAV
   XML element names, though their namespace differs.  Care must be
   taken not to confuse the two sets of names.

   Processing of XML by CalDAV clients and servers MUST follow the rules
   described in [RFC2518], in particular Section 14, and Appendices 3
   and 4 of that specification.

1.3.  Method Preconditions and Postconditions

   A "precondition" of a method describes the state of the server that
   must be true for that method to be performed.  A "postcondition" of a
   method describes the state of the server that must be true after that
   method has been completed.  If a method precondition or postcondition
   for a request is not satisfied, the response status of the request
   MUST be either 403 (Forbidden) if the request should not be repeated
   because it will always fail, or 409 (Conflict) if it is expected that
   the user might be able to resolve the conflict and resubmit the
   request.

   In order to allow better client handling of 403 and 409 responses, a
   distinct XML element type is associated with each method precondition
   and postcondition of a request.  When a particular precondition is
   not satisfied or a particular postcondition cannot be achieved, the
   appropriate XML element MUST be returned as the child of a top-level
   DAV:error element in the response body, unless otherwise negotiated
   by the request.


2.  Requirements Overview

   This section lists what functionality is required of a CalDAV server.
   To advertise support for CalDAV, a server:

   o  MUST support iCalendar [RFC2445] as a media type for calendar
      object resource format;

   o  MUST support WebDAV Class 1 [RFC2518] (note that [I-D.ietf-webdav-
      rfc2518bis] describes clarifications to [RFC2518] that aid
      interoperability);

   o  MUST support WebDAV ACL [RFC3744] with the additional privilege
      defined in Section 6.1 of this document;

   o  MUST support transport over TLS [RFC2246] as defined in [RFC2818]
      (note that [RFC2246] has been obsoleted by [RFC4346]);





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   o  MUST support ETags [RFC2616] with additional requirements
      specified in Section 5.3.4 of this document;

   o  MUST support all calendaring REPORTs defined in Section 7 of this
      document; and

   o  MUST advertise support on all calendar collections and calendar
      object resources for the calendaring REPORTs in the DAV:supported-
      report-set property as defined in Versioning Extensions to WebDAV
      [RFC3253].

   In addition, a server:

   o  SHOULD support the MKCALENDAR method defined in Section 5.3.1 of
      this document.


3.  Calendaring Data Model

   One of the features which has made WebDAV a successful protocol is
   its firm data model.  This makes it a useful framework for other
   applications such as calendaring.  This specification follows the
   same pattern by developing all features based on a well-described
   data model.

   As a brief overview, a CalDAV calendar is modeled as a WebDAV
   collection with a defined structure; each calendar collection
   contains a number of resources representing calendar objects as its
   direct child resource.  Each resource representing a calendar object
   (event or to-do, or journal entry, or other calendar components) is
   called a "calendar object resource".  Each calendar object resource
   and each calendar collection can be individually locked and have
   individual WebDAV properties.  Requirements derived from this model
   are provided in Section 4.1 and Section 4.2.

3.1.  Calendar Server

   A CalDAV server is a calendaring-aware engine combined with a WebDAV
   repository.  A WebDAV repository is a set of WebDAV collections,
   containing other WebDAV resources, within a unified URL namespace.
   For example, the repository "http://www.example.com/webdav/" may
   contain WebDAV collections and resources, all of which have URLs
   beginning with "http://www.example.com/webdav/".  Note that the root
   URL "http://www.example.com/" may not itself be a WebDAV repository
   (for example, if the WebDAV support is implemented through a servlet
   or other Web server extension).

   A WebDAV repository MAY include calendar data in some parts of its



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   URL namespace, and non-calendaring data in other parts.

   A WebDAV repository can advertise itself as a CalDAV server if it
   supports the functionality defined in this specification at any point
   within the root of the repository.  That might mean that calendaring
   data is spread throughout the repository and mixed with non-calendar
   data in nearby collections (e.g., calendar data may be found in
   /home/lisa/calendars/ as well as in /home/bernard/calendars/, and
   non-calendar data in /home/lisa/contacts/).  Or, it might mean that
   calendar data can be found only in certain sections of the repository
   (e.g., /calendar/).  Calendaring features are only required in the
   repository sections that are or contain calendar object resources.
   So a repository confining calendar data to the /calendar/ collection
   would only need to support the CalDAV required features within that
   collection.

   The CalDAV server or repository is the canonical location for
   calendar data and state information.  Clients may submit requests to
   change data or download data.  Clients may store calendar objects
   offline and attempt to synchronize at a later time.  However, clients
   MUST be prepared for calendar data on the server to change between
   the time of last synchronization and when attempting an update, as
   calendar collections may be shared and accessible via multiple
   clients.  Entity tags and other features make this possible.

3.2.  Recurrence and the Data Model

   Recurrence is an important part of the data model because it governs
   how many resources are expected to exist.  This specification models
   a recurring calendar component and its recurrence exceptions as a
   single resource.  In this model, recurrence rules, recurrence dates,
   exception rules, and exception dates are all part of the data in a
   single calendar object resource.  This model avoids problems of
   limiting how many recurrence instances to store in the repository,
   how to keep recurrence instances in sync with the recurring calendar
   component, and how to link recurrence exceptions with the recurring
   calendar component.  It also results in less data to synchronize
   between client and server, and makes it easier to make changes to all
   recurrence instances or to a recurrence rule.  It makes it easier to
   create a recurring calendar component, and easier to delete all
   recurrence instances.

   Clients are not forced to retrieve information about all recurrence
   instances of a recurring component.  The CALDAV:calendar-query and
   CALDAV:calendar-multiget REPORTs defined in this document allow
   clients to retrieve only recurrence instances that overlap a given
   time range.




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4.  Calendar Resources

4.1.  Calendar Object Resources

   Calendar object resources contained in calendar collections MUST NOT
   contain more than one type of calendar component (e.g., VEVENT,
   VTODO, VJOURNAL, VFREEBUSY, etc.) with the exception of VTIMEZONE
   components which MUST be specified for each unique TZID parameter
   value specified in the iCalendar object.  For instance, a calendar
   object resource can contain two VEVENT components and one VTIMEZONE
   component, but it cannot contain one VEVENT component and one VTODO
   component.  Instead the VEVENT and VTODO components would have to be
   stored in separate calendar object resources in the same collection.

   Calendar object resources contained in calendar collections MUST NOT
   specify the iCalendar METHOD property.

   The UID property value of the calendar components contained in a
   calendar object resource MUST be unique in the scope of the calendar
   collection in which they are stored.

   Calendar components in a calendar collection that have different UID
   property values MUST be stored in separate calendar object resources.

   Calendar components with the same UID property value, in a given
   calendar collection, MUST be contained in the same calendar object
   resource.  This ensures that all components in a recurrence "set" are
   contained in the same calendar object resource.  It is possible for a
   calendar object resource to just contain components that represent
   "overridden" instances (ones which modify the behavior of a regular
   instance, and thus include a RECURRENCE-ID property), without also
   including the "master" recurring component (the one that defines the
   recurrence "set" and does not contain any "RECURRENCE-ID" property).

   For example, given the following iCalendar object:
















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    BEGIN:VCALENDAR
    PRODID:-//Example Corp.//CalDAV Client//EN
    VERSION:2.0
    BEGIN:VEVENT
    UID:1@example.com
    SUMMARY:One-off Meeting
    DTSTAMP:20041210T183904Z
    DTSTART:20041207T120000Z
    DTEND:20041207T130000Z
    END:VEVENT
    BEGIN:VEVENT
    UID:2@example.com
    SUMMARY:Weekly Meeting
    DTSTAMP:20041210T183838Z
    DTSTART:20041206T120000Z
    DTEND:20041206T130000Z
    RRULE:FREQ=WEEKLY
    END:VEVENT
    BEGIN:VEVENT
    UID:2@example.com
    SUMMARY:Weekly Meeting
    RECURRENCE-ID:20041213T120000Z
    DTSTAMP:20041210T183838Z
    DTSTART:20041213T130000Z
    DTEND:20041213T140000Z
    END:VEVENT
    END:VCALENDAR

   The VEVENT component with the UID value "1@example.com", would be
   stored in its own calendar object resource.  The two VEVENT
   components with the UID value "2@example.com", which represent a
   recurring event where one recurrence instance has been overridden,
   would be stored in the same calendar object resource.

4.2.  Calendar Collection

   A calendar collection contains calendar object resources that
   represent calendar components within a calendar.  A calendar
   collection is manifested to clients as a WebDAV resource collection
   identified by a URL.  A calendar collection MUST report the DAV:
   collection and CALDAV:calendar XML elements in the value of the DAV:
   resourcetype property.  The element type declaration for CALDAV:
   calendar is:

       <!ELEMENT calendar EMPTY>

   A calendar collection can be created through provisioning (e.g.,
   automatically created when a user's account is provisioned), or it



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   can be created with the MKCALENDAR method (see Section 5.3.1).  This
   method can be useful for a user to create additional calendars (e.g.,
   soccer schedule) or for users to share a calendar (e.g., team events
   or conference room).  Note however that this document doesn't define
   what extra calendar collections are for.  Users must rely on non-
   standard cues to find out what a calendar collection is for, or use
   the CALDAV:calendar-description property defined in Section 5.2.1 to
   provide such a cue.

   The following restrictions are applied to the resources within a
   calendar collection:

   a.  Calendar collections MUST only contain calendar object resources
       and collections that are not calendar collections. i.e., the only
       "top-level" non-collection resources allowed in a calendar
       collection are calendar object resources.  This ensures that
       calendar clients do not have to deal with non-calendar data in a
       calendar collection, though they do have to distinguish between
       calendar object resources and collections when using standard
       WebDAV techniques to examine the contents of a collection.

   b.  Collections contained in calendar collections MUST NOT contain
       calendar collections at any depth. i.e., "nesting" of calendar
       collections within other calendar collections at any depth is not
       allowed.  This specification does not define how collections
       contained in a calendar collection are used or how they relate to
       any calendar object resources contained in the calendar
       collection.

   Multiple calendar collections MAY be children of the same collection.


5.  Calendar Access Feature

5.1.  Calendar Access Support

   A server supporting the features described in this document MUST
   include "calendar-access" 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-
   access" in the DAV response header MUST indicate that the server
   supports all MUST level requirements specified in this document.









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5.1.1.  Example: Using OPTIONS for the Discovery of Calendar Access
        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
   Date: Fri, 11 Nov 2005 09:32:12 GMT
   Content-Length: 0

   In this example, the OPTIONS method returns the value "calendar-
   access" in the DAV response header to indicate that the collection
   "/home/bernard/calendars/" supports the properties, reports, methods,
   or privileges defined in this specification.

5.2.  Calendar Collection Properties

   This section defines properties that MAY be defined on calendar
   collections.

5.2.1.  CALDAV:calendar-description Property

   Name: calendar-description

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

   Purpose: Provides a human-readable description of the calendar
      collection.

   Conformance: This property MAY be defined on any calendar collection.
      If defined, it MAY be protected and SHOULD NOT be returned by a
      PROPFIND DAV:allprop request (as defined in Section 12.14.1 of
      [RFC2518]).  An xml:lang attribute indicating the human language
      of the description SHOULD be set for this property by clients or
      through server provisioning.  Servers MUST return any xml:lang
      attribute if set for the property.

   Description: If present, the property contains a description of the
      calendar collection that is suitable for presentation to a user.
      If not present, the client should assume no description for the
      calendar collection.



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   Definition:

         <!ELEMENT calendar-description (#PCDATA)>
         PCDATA value: string

   Example:

         <C:calendar-description xml:lang="fr-CA"
            xmlns:C="urn:ietf:params:xml:ns:caldav"
         >Calendrier de Mathilde Desruisseaux</C:calendar-description>

5.2.2.  CALDAV:calendar-timezone Property

   Name: calendar-timezone

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

   Purpose: Specifies a time zone on a calendar collection.

   Conformance: This property SHOULD be defined on all calendar
      collections.  If defined, it SHOULD NOT be returned by a PROPFIND
      DAV:allprop request (as defined in Section 12.14.1 of [RFC2518]).

   Description: The CALDAV:calendar-timezone property is used to specify
      the time zone the server should rely on to resolve "date" values
      and "date with local time" values (i.e., floating time) to "date
      with UTC time" values.  The server will require this information
      to determine if a calendar component scheduled with "date" values
      or "date with local time" values overlaps a CALDAV:time-range
      specified in a CALDAV:calendar-query REPORT.  The server will also
      require this information to compute the proper FREEBUSY time
      period as "date with UTC time" in the VFREEBUSY component returned
      in a response to a CALDAV:free-busy-query REPORT request that
      takes into account calendar components scheduled with "date"
      values or "date with local time" values.  In the absence of this
      property the server MAY rely on the time zone of their choice.

   Note: The iCalendar data embedded within the CALDAV:calendar-timezone
      XML element MUST follow the standard XML character data encoding
      rules, including use of &lt;, &gt;, &amp; etc entity encoding or
      the use of a <![CDATA[ ... ]]> construct.  In the later case the
      iCalendar data cannot contain the character sequence "]]>" which
      is the end delimiter for the CDATA section.

   Definition:

         <!ELEMENT calendar-timezone (#PCDATA)>
         PCDATA value: an iCalendar object with exactly one VTIMEZONE



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               component.

   Example:

   <C:calendar-timezone
       xmlns:C="urn:ietf:params:xml:ns:caldav">BEGIN:VCALENDAR
   PRODID:-//Example Corp.//CalDAV Client//EN
   VERSION:2.0
   BEGIN:VTIMEZONE
   TZID:US-Eastern
   LAST-MODIFIED:19870101T000000Z
   BEGIN:STANDARD
   DTSTART:19671029T020000
   RRULE:FREQ=YEARLY;BYDAY=-1SU;BYMONTH=10
   TZOFFSETFROM:-0400
   TZOFFSETTO:-0500
   TZNAME:Eastern Standard Time (US &amp; Canada)
   END:STANDARD
   BEGIN:DAYLIGHT
   DTSTART:19870405T020000
   RRULE:FREQ=YEARLY;BYDAY=1SU;BYMONTH=4
   TZOFFSETFROM:-0500
   TZOFFSETTO:-0400
   TZNAME:Eastern Daylight Time (US &amp; Canada)
   END:DAYLIGHT
   END:VTIMEZONE
   END:VCALENDAR
   </C:calendar-timezone>

5.2.3.  CALDAV:supported-calendar-component-set Property

   Name: supported-calendar-component-set

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

   Purpose: Specifies the calendar component types (e.g., VEVENT, VTODO,
      etc.) that calendar object resources can contain 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:supported-calendar-component-set property is
      used to specify restrictions on the calendar component types that
      calendar object resources may contain in a calendar collection.
      Any attempt by the client to store calendar object resources with



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      component types not listed in this property, if it exists, MUST
      result in an error, with the CALDAV:supported-calendar-component
      precondition (Section 5.3.2.1) 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.  The empty-element tag <C:comp name="VTIMEZONE"/> MUST
      only be specified if support for calendar object resources that
      only contain VTIMEZONE components is provided or desired.  Support
      for VTIMEZONE components in calendar object resources that contain
      VEVENT or VTODO components is always assumed.  In the absence of
      this property the server MUST accept all component types, and the
      client can assume that.

   Definition:

         <!ELEMENT supported-calendar-component-set (comp*)>

   Example:

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

5.2.4.  CALDAV:supported-calendar-data Property

   Name: supported-calendar-data

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

   Purpose: Specifies what media types are allowed for calendar object
      resources in a 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:supported-calendar-data property is used to
      specify the media type supported for the calendar object resources
      contained in a given calendar collection (e.g., iCalendar version
      2.0).  Any attempt by the client to store calendar object
      resources with a media type not listed in this property MUST
      result in an error, with the CALDAV:supported-calendar-data
      precondition (Section 5.3.2.1) being violated.  In the absence of
      this property the server MUST only accept data with the media type



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      "text/calendar" and iCalendar version 2.0, and clients can assume
      that.

   Definition:

         <!ELEMENT supported-calendar-data (calendar-data*)>

   Example:

         <C:supported-calendar-data
            xmlns:C="urn:ietf:params:xml:ns:caldav">
           <C:calendar-data content-type="text/calendar" version="2.0"/>
         </C:supported-calendar-data>

5.2.5.  CALDAV:max-resource-size Property

   Name: max-resource-size

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

   Purpose: Provides a numeric value indicating the maximum size of
      resource in octets that the server is willing to accept when a
      calendar object resource is stored in a 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:max-resource-size is used to specify a
      numeric value that represents the maximum size in octets that the
      server is willing to accept when a calendar object resource is
      stored in a calendar collection.  Any attempt to store a calendar
      object resource exceeding this size MUST result in an error, with
      the CALDAV:max-resource-size precondition (Section 5.3.2.1) being
      violated.  In the absence of this property the client can assume
      that the server will allow storing a resource of any reasonable
      size.

   Definition:

         <!ELEMENT max-resource-size (#PCDATA)>
         PCDATA value: a numeric value (positive integer)








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   Example:

         <C:max-resource-size xmlns:C="urn:ietf:params:xml:ns:caldav"
         >102400</C:max-resource-size>

5.2.6.  CALDAV:min-date-time Property

   Name: min-date-time

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

   Purpose: Provides a date-time value indicating the earliest date and
      time (in UTC) that the server is willing to accept for any date or
      time value in a calendar object resource stored in a 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:min-date-time is used to specify an iCalendar
      DATE-TIME value in UTC that indicates the earliest inclusive date
      that the server is willing to accept for any explicit date or time
      value in a calendar object resource stored in a calendar
      collection.  Any attempt to store a calendar object resource using
      a date or time value earlier than this value MUST result in an
      error, with the CALDAV:min-date-time precondition
      (Section 5.3.2.1) being violated.  Note that servers MUST accept
      recurring components that specify instances beyond this limit,
      provided none of those instances have been overridden.  In that
      case the server MAY simply ignore those instances outside of the
      acceptable range when processing reports on the calendar object
      resource.  In the absence of this property the client can assume
      any valid iCalendar date may be used at least up to the CALDAV:
      max-date-time value if that is defined.

   Definition:

         <!ELEMENT min-date-time (#PCDATA)>
         PCDATA value: an iCalendar format DATE-TIME value in UTC

   Example:

         <C:min-date-time xmlns:C="urn:ietf:params:xml:ns:caldav"
         >19000101T000000Z</C:min-date-time>





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5.2.7.  CALDAV:max-date-time Property

   Name: max-date-time

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

   Purpose: Provides a date-time value indicating the latest date and
      time (in UTC) that the server is willing to accept for any date or
      time value in a calendar object resource stored in a 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:max-date-time is used to specify an iCalendar
      DATE-TIME value in UTC that indicates the inclusive latest date
      that the server is willing to accept for any date or time value in
      a calendar object resource stored in a calendar collection.  Any
      attempt to store a calendar object resource using a date or time
      value later than this value MUST result in an error, with the
      CALDAV:max-date-time precondition (Section 5.3.2.1) being
      violated.  Note that servers MUST accept recurring components that
      specify instances beyond this limit, provided none of those
      instances have been overridden.  In that case the server MAY
      simply ignore those instances outside of the acceptable range when
      processing reports on the calendar object resource.  In the
      absence of this property the client can assume any valid iCalendar
      date may be used at least down to the CALDAV:min-date-time value
      if that is defined.

   Definition:

         <!ELEMENT max-date-time (#PCDATA)>
         PCDATA value: an iCalendar format DATE-TIME value in UTC

   Example:

         <C:max-date-time xmlns:C="urn:ietf:params:xml:ns:caldav"
         >20491231T235959Z</C:max-date-time>

5.2.8.  CALDAV:max-instances Property








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   Name: max-instances

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

   Purpose: Provides a numeric value indicating the maximum number of
      recurrence instances that a calendar object resource stored in a
      calendar collection can generate.

   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:max-instances is used to specify a numeric
      value that indicates the maximum number of recurrence instances
      that a calendar object resource stored in a calendar collection
      can generate.  Any attempt to store a calendar object resource
      with a recurrence pattern that generates more instances than this
      value MUST result in an error, with the CALDAV:max-instances
      precondition (Section 5.3.2.1) being violated.  In the absence of
      this property the client can assume that the server has no limits
      on the number of recurrence instances it can handle or expand.

   Definition:

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

   Example:

         <C:max-instances xmlns:C="urn:ietf:params:xml:ns:caldav"
         >100</C:max-instances>

5.2.9.  CALDAV:max-attendees-per-instance Property

   Name: max-attendees-per-instance

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

   Purpose: Provides a numeric value indicating the maximum number of
      ATTENDEE properties in any instance of a calendar object resource
      stored in a 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]).




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   Description: The CALDAV:max-attendees-per-instance is used to specify
      a numeric value that indicates the maximum number of iCalendar
      ATTENDEE properties on any one instance of a calendar object
      resource stored in a calendar collection.  Any attempt to store a
      calendar object resource with more ATTENDEE properties per
      instance than this value MUST result in an error, with the CALDAV:
      max-attendees-per-instance precondition (Section 5.3.2.1) being
      violated.  In the absence of this property the client can assume
      that the server can handle any number of ATTENDEE properties in a
      calendar component.

   Definition:

         <!ELEMENT max-attendees-per-instance (#PCDATA)>
         PCDATA value: a numeric value (integer greater than zero)

   Example:

         <C:max-attendees-per-instance
              xmlns:C="urn:ietf:params:xml:ns:caldav"
         >25</C:max-attendees-per-instance>

5.2.10.  Additional Precondition for PROPPATCH

   This specification requires an additional Precondition for the
   PROPPATCH method.  The precondition is:

      (CALDAV:valid-calendar-data): The time zone specified in CALDAV:
      calendar-timezone property MUST be a valid iCalendar object
      containing a single valid VTIMEZONE component.

5.3.  Creating Resources

   The creation of calendar collections and calendar object resources
   may be initiated by either a CalDAV client or by the CalDAV server.
   For example, a server might come pre-configured with a user's
   calendar collection, or the CalDAV client might request the server to
   create a new calendar collection for a given user.  Servers might
   populate events as calendar objects inside a calendar collection, or
   clients might request the server to create events.  Either way, both
   client and server MUST comply with the requirements in this document,
   and MUST understand objects appearing in calendar collections or
   according to the data model defined here.

5.3.1.  MKCALENDAR Method

   An HTTP request using the MKCALENDAR method creates a new calendar
   collection resource.  A server MAY restrict calendar collection



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   creation to particular collections.

   Support for MKCALENDAR on the server is only RECOMMENDED and not
   REQUIRED because some calendar stores only support one calendar per
   user (or principal) and those are typically pre-created for each
   account.  However, servers and clients are strongly encouraged to
   support MKCALENDAR whenever possible to allow users to create
   multiple calendar collections to better help organize their data.

   Clients SHOULD use the DAV:displayname property for a human-readable
   name of the calendar.  Clients can either specify the value of the
   DAV:displayname property in the request body of the MKCALENDAR
   request, or alternatively issue a PROPPATCH request to change the
   DAV:displayname property to the appropriate value immediately after
   issuing the MKCALENDAR request.  Clients SHOULD NOT set the DAV:
   displayname property to be the same as any other calendar collection
   at the same URI "level".  When displaying calendar collections to
   users, clients SHOULD check the DAV:displayname property and use that
   value as the name of the calendar.  In the event that the DAV:
   displayname property is empty, the client MAY use the last part of
   the calendar collection URI as the name, however that path segment
   may be "opaque" and not represent any meaningful human-readable text.

   If a MKCALENDAR request fails, the server state preceding the request
   MUST be restored.

   Marshalling:

      If a request body is included, it MUST be a CALDAV:mkcalendar XML
      element.  Instruction processing MUST occur in the order
      instructions are received (i.e., from top to bottom).
      Instructions MUST either all be executed or none executed.  Thus
      if any error occurs during processing, all executed instructions
      MUST be undone and a proper error result returned.  Instruction
      processing details can be found in the definition of the DAV:set
      instruction in Section 12.13.2 of [RFC2518].

         <!ELEMENT mkcalendar (DAV:set)>

      If a response body for a successful request is included, it MUST
      be a CALDAV:mkcalendar-response XML element.

         <!ELEMENT mkcalendar-response ANY>

      The response MUST include a Cache-Control:no-cache header.

   Preconditions:




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      (DAV:resource-must-be-null): A resource MUST NOT exist at the
      Request-URI;

      (CALDAV:calendar-collection-location-ok): The Request-URI MUST
      identify a location where a calendar collection can be created;

      (CALDAV:valid-calendar-data): The time zone specified in the
      CALDAV:calendar-timezone property MUST be a valid iCalendar object
      containing a single valid VTIMEZONE component;

      (DAV:needs-privilege): The DAV:bind privilege MUST be granted to
      the current user on the parent collection of the Request-URI.

   Postconditions:

      (CALDAV:initialize-calendar-collection): A new calendar collection
      exists at the Request-URI.  The DAV:resourcetype of the calendar
      collection MUST contain both DAV:collection and CALDAV:calendar
      XML elements.

5.3.1.1.  Status Codes

   The following are examples of response codes one would expect to get
   in a response to a MKCALENDAR request.  Note that this list is by no
   means exhaustive.

      201 (Created) - The calendar collection resource was created in
      its entirety;

      207 (Multi-Status) - The calendar collection resource was not
      created since one or more DAV:set instructions specified in the
      request body could not be processed successfully.  The following
      are examples of response codes one would expect to be used in a
      207 (Multi-Status) response in this situation:

         403 (Forbidden) - The client, for reasons the server chooses
         not to specify, cannot alter one of the properties;

         409 (Conflict) - The client has provided a value whose
         semantics are not appropriate for the property.  This includes
         trying to set read-only properties;

         424 (Failed Dependency) - The DAV:set instruction on the
         specified resource would have succeeded if it were not for the
         failure of another DAV:set instruction specified in the request
         body;





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         423 (Locked) - The specified resource is locked and the client
         either is not a lock owner or the lock type requires a lock
         token to be submitted and the client did not submit it; and

         507 (Insufficient Storage) - The server did not have sufficient
         space to record the property;

      403 (Forbidden) - This indicates at least one of two conditions:
      1) the server does not allow the creation of calendar collections
      at the given location in its namespace, or 2) the parent
      collection of the Request-URI exists but cannot accept members;

      409 (Conflict) - A collection cannot be made at the Request-URI
      until one or more intermediate collections have been created;

      415 (Unsupported Media Type) - The server does not support the
      request type of the body; and

      507 (Insufficient Storage) - The resource does not have sufficient
      space to record the state of the resource after the execution of
      this method.

5.3.1.2.  Example: Successful MKCALENDAR request

   This example creates a calendar collection called /home/lisa/
   calendars/events/ on the server cal.example.com with specific values
   for the properties DAV:displayname, CALDAV:calendar-description,
   CALDAV:supported-calendar-component-set, and CALDAV:calendar-
   timezone.






















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   >> Request <<

   MKCALENDAR /home/lisa/calendars/events/ HTTP/1.1
   Host: cal.example.com
   Content-Type: application/xml; charset="utf-8"
   Content-Length: xxxx

   <?xml version="1.0" encoding="utf-8" ?>
   <C:mkcalendar xmlns:D="DAV:"
                 xmlns:C="urn:ietf:params:xml:ns:caldav">
     <D:set>
       <D:prop>
         <D:displayname>Lisa's Events</D:displayname>
         <C:calendar-description xml:lang="en"
   >Calendar restricted to events.</C:calendar-description>
         <C:supported-calendar-component-set>
           <C:comp name="VEVENT"/>
         </C:supported-calendar-component-set>
         <C:calendar-timezone><![CDATA[BEGIN:VCALENDAR
   PRODID:-//Example Corp.//CalDAV Client//EN
   VERSION:2.0
   BEGIN:VTIMEZONE
   TZID:US-Eastern
   LAST-MODIFIED:19870101T000000Z
   BEGIN:STANDARD
   DTSTART:19671029T020000
   RRULE:FREQ=YEARLY;BYDAY=-1SU;BYMONTH=10
   TZOFFSETFROM:-0400
   TZOFFSETTO:-0500
   TZNAME:Eastern Standard Time (US & Canada)
   END:STANDARD
   BEGIN:DAYLIGHT
   DTSTART:19870405T020000
   RRULE:FREQ=YEARLY;BYDAY=1SU;BYMONTH=4
   TZOFFSETFROM:-0500
   TZOFFSETTO:-0400
   TZNAME:Eastern Daylight Time (US & Canada)
   END:DAYLIGHT
   END:VTIMEZONE
   END:VCALENDAR
   ]]></C:calendar-timezone>
       </D:prop>
     </D:set>
   </C:mkcalendar>







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   >> Response <<

   HTTP/1.1 201 Created
   Cache-Control: no-cache
   Date: Fri, 11 Nov 2005 09:32:12 GMT
   Content-Length: 0

5.3.2.  Creating Calendar Object Resources

   Clients populate calendar collections with calendar object resources.
   The URL for each calendar object resource is entirely arbitrary, and
   does not need to bear a specific relationship to the calendar object
   resource's iCalendar properties or other metadata.  New calendar
   object resources MUST be created with a PUT request targeted at an
   unmapped URI.  A PUT request targeted at a mapped URI updates an
   existing calendar object resource.

   When servers create new resources, it's not hard for the server to
   choose an unmapped URI.  It's slightly tougher for clients, because a
   client might not want to examine all resources in the collection, and
   might not want to lock the entire collection to ensure that a new
   resource isn't created with a name collision.  However, there is an
   HTTP feature to mitigate this.  If the client intends to create a new
   non-collection resource, such as a new VEVENT, the client SHOULD use
   the HTTP request header "If-None-Match: *" on the PUT request.  The
   Request-URI on the PUT request MUST include the target collection,
   where the resource is to be created, plus the name of the resource in
   the last path segment.  The "If-None-Match: *" request header ensures
   that the client will not inadvertently overwrite an existing
   resource, if the last path segment turned out to already be used.





















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   >> Request <<

   PUT /home/lisa/calendars/events/qwue23489.ics HTTP/1.1
   If-None-Match: *
   Host: cal.example.com
   Content-Type: text/calendar
   Content-Length: xxxx

   BEGIN:VCALENDAR
   VERSION:2.0
   PRODID:-//Example Corp.//CalDAV Client//EN
   BEGIN:VEVENT
   UID:20010712T182145Z-123401@example.com
   DTSTAMP:20060712T182145Z
   DTSTART:20060714T170000Z
   DTEND:20060715T040000Z
   SUMMARY:Bastille Day Party
   END:VEVENT
   END:VCALENDAR

   >> Response <<

   HTTP/1.1 201 Created
   Content-Length: 0
   Date: Fri, 11 Nov 2005 09:32:12 GMT
   ETag: "123456789-000-111"

   The request to change an existing event is the same, but with a
   specific ETag in the "If-Match" header, rather than the "If-None-
   Match" header.

   As indicated in Section 3.10 of [RFC2445], the URL of calendar object
   resources containing (an arbitrary set of) calendaring and scheduling
   information may be suffixed by ".ics", and the URL of calendar object
   resources containing free or busy time information may be suffixed by
   ".ifb".

5.3.2.1.  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 calendar object resource into a calendar
      collection occurs.

      When a COPY or MOVE operation of a calendar object resource into a
      calendar collection occurs.




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   The new preconditions are:

      (CALDAV:supported-calendar-data): The resource submitted in the
      PUT request, or targeted by a COPY or MOVE request MUST be a
      supported media type (i.e., iCalendar) for calendar object
      resources;

      (CALDAV:valid-calendar-data): The resource submitted in the PUT
      request, or targeted by a COPY or MOVE request MUST be valid data
      for the media type being specified (i.e., MUST contain valid
      iCalendar data);

      (CALDAV:valid-calendar-object-resource): The resource submitted in
      the PUT request, or targeted by a COPY or MOVE request MUST obey
      all restrictions specified in Section 4.1 (e.g., calendar object
      resources MUST NOT contain more than one type of calendar
      component, calendar object resources MUST NOT specify the
      iCalendar METHOD property, etc.);

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

      (CALDAV:no-uid-conflict): The resource submitted in the PUT
      request, or targeted by a COPY or MOVE request MUST NOT specify an
      iCalendar UID property value already in use in the targeted
      calendar collection or overwrite an existing calendar object
      resource with one that has a different UID property value.
      Servers SHOULD report the URL of the resource that is already
      making use of the same UID property value in the DAV:href element;

                <!ELEMENT no-uid-conflict (DAV:href)>

      (CALDAV:calendar-collection-location-ok): In a COPY or MOVE
      request, when the Request-URI is a calendar collection, the
      Destination-URI MUST identify a location where a calendar
      collection can be created;

      (CALDAV:max-resource-size): The resource submitted in the PUT
      request, or targeted by a COPY or MOVE request MUST have an octet
      size less than or equal to the value of the CALDAV:max-resource-
      size property value (Section 5.2.5) on the calendar collection
      where the resource will be stored;

      (CALDAV:min-date-time): The resource submitted in the PUT request,
      or targeted by a COPY or MOVE request MUST have all of its
      iCalendar date or time property values (for each recurring



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      instance) greater than or equal to the value of the CALDAV:min-
      date-time property value (Section 5.2.6) on the calendar
      collection where the resource will be stored;

      (CALDAV:max-date-time): The resource submitted in the PUT request,
      or targeted by a COPY or MOVE request MUST have all of its
      iCalendar date or time property values (for each recurring
      instance) less than the value of the CALDAV:max-date-time property
      value (Section 5.2.7) on the calendar collection where the
      resource will be stored;

      (CALDAV:max-instances): The resource submitted in the PUT request,
      or targeted by a COPY or MOVE request MUST generate a number of
      recurring instances less than or equal to the value of the CALDAV:
      max-instances property value (Section 5.2.8) on the calendar
      collection where the resource will be stored;

      (CALDAV:max-attendees-per-instance): The resource submitted in the
      PUT request, or targeted by a COPY or MOVE request MUST have a
      number of ATTENDEE properties on any one instance less than or
      equal to the value of the CALDAV:max-attendees-per-instance
      property value (Section 5.2.9) on the calendar collection where
      the resource will be stored;

5.3.3.  Non-standard components, properties and parameters

   iCalendar provides a "standard mechanism for doing non-standard
   things".  This extension support allows implementers to make use of
   non-standard components, properties and parameters whose names are
   prefixed with the text "X-".

   Servers MUST support the use of non-standard components, properties
   and parameters in calendar object resources stored via the PUT
   method.

   Servers may need to enforce rules for their own "private" components,
   properties or parameters, so servers MAY reject any attempt by the
   client to change those or use values for those outside of any
   restrictions the server may have.  Servers SHOULD ensure that any
   "private" components, properties or parameters it uses follow the
   convention of including a vendor id in the "X-" name as described in
   Section 4.2 of [RFC2445], e.g., "X-ABC-Private".

5.3.4.  Calendar Object Resource Entity Tag

   The DAV:getetag property MUST be defined and set to a strong entity
   tag on all calendar object resources.




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   A response to a GET request targeted at a calendar object resource
   MUST contain an ETag response header field indicating the current
   value of the strong entity tag of the calendar object resource.

   Servers SHOULD return a strong entity tag (ETag header) in a PUT
   response when the stored calendar object resource is equivalent by
   octet equality to the calendar object resource submitted in the body
   of the PUT request.  This allows clients to reliably use the returned
   strong entity tag for data synchronization purposes.  For instance,
   the client can do a PROPFIND request on the stored calendar object
   resource and have the DAV:getetag property returned, and compare that
   value with the strong entity tag it received on the PUT response, and
   know that if they are equal, then the calendar object resource on the
   server has not been changed.

   In the case where the data stored by a server as a result of a PUT
   request is not equivalent by octet equality to the submitted calendar
   object resource, the behavior of the ETag response header is not
   specified here, with the exception that a strong entity tag MUST NOT
   be returned in the response.  As a result, clients may need to
   retrieve the modified calendar object resource (and ETag) as a basis
   for further changes, rather than use the calendar object resource it
   had sent with the PUT request.


6.  Calendaring Access Control

6.1.  Calendaring Privilege

   CalDAV servers MUST support and adhere to the requirements of WebDAV
   ACL [RFC3744].  WebDAV ACL provides a framework for an extensible set
   of privileges that can be applied to WebDAV collections and ordinary
   resources.  CalDAV servers MUST also support the calendaring
   privilege defined in this section.

6.1.1.  CALDAV:read-free-busy Privilege

   Calendar users often wish to allow other users to see their busy time
   information, without viewing the other details of the calendar
   components (e.g., location, summary, attendees).  This allows a
   significant amount of privacy while still allowing other users to
   schedule meetings at times when the user is likely to be free.

   The CALDAV:read-free-busy privilege controls which calendar
   collections, regular collections and calendar object resources are
   examined when a CALDAV:free-busy-query REPORT request is processed
   (see Section 7.10).  This privilege can be granted on calendar
   collections, regular collections or calendar object resources.



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   Servers MUST support this privilege on all calendar collections,
   regular collections and calendar object resources.


           <!ELEMENT read-free-busy EMPTY>

   The CALDAV:read-free-busy privilege MUST be aggregated in the DAV:
   read privilege.  Servers MUST allow the CALDAV:read-free-busy to be
   granted without the DAV:read privilege being granted.

   Clients should note that when only the CALDAV:read-free-busy
   privilege has been granted on a resource, this does not imply access
   to GET, HEAD, OPTIONS and PROPFIND on the resource -- those
   operations are governed by the DAV:read privilege.

6.2.  Additional Principal Property

   This section defines an additional property for WebDAV principal
   resources as defined in [RFC3744].

6.2.1.  CALDAV:calendar-home-set Property

   Name: calendar-home-set

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

   Purpose: Identifies the URL of any WebDAV collections that contain
      calendar collections owned by the associated principal resource.

   Conformance: This property SHOULD be defined on a principal resource.
      If defined, it MAY 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:calendar-home-set property is meant to allow
      users to easily find the calendar collections owned by the
      principal.  Typically, users will group all the calendar
      collections that they own under a common collection.  This
      property specifies the URL of collections that either are calendar
      collections or ordinary collections that have child or descendant
      calendar collections owned by the principal.

   Definition:

         <!ELEMENT calendar-home-set (DAV:href*)>






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   Example:

       <C:calendar-home-set xmlns:D="DAV:"
                            xmlns:C="urn:ietf:params:xml:ns:caldav">
         <D:href>http://cal.example.com/home/bernard/calendars/</D:href>
       </C:calendar-home-set>


7.  Calendaring Reports

   This section defines the REPORTs that CalDAV servers MUST support on
   calendar collections and calendar object resources.

   CalDAV servers MUST advertise support for these REPORTs on all
   calendar collections and calendar object resources with the DAV:
   supported-report-set property defined in Section 3.1.5 of [RFC3253].
   CalDAV servers MAY also advertise support for these REPORTs on
   ordinary collections.

   Some of these REPORTs allow calendar data (from possibly multiple
   resources) to be returned.

7.1.  REPORT Method

   The REPORT method (defined in Section 3.6 of [RFC3253]) provides an
   extensible mechanism for obtaining information about one or more
   resources.  Unlike the PROPFIND method, which returns the value of
   one or more named properties, the REPORT method can involve more
   complex processing.  REPORT is valuable in cases where the server has
   access to all of the information needed to perform the complex
   request (such as a query), and where it would require multiple
   requests for the client to retrieve the information needed to perform
   the same request.

   CalDAV servers MUST support the DAV:expand-property REPORT defined in
   Section 3.8 of [RFC3253].

7.2.  Ordinary collections

   Servers MAY support the REPORTs defined in this document on ordinary
   collections (collections that are not calendar collections) in
   addition to calendar collections or calendar object resources.  In
   computing responses to the REPORTs on ordinary collections, servers
   MUST only consider calendar object resources contained in calendar
   collections that are targeted by the REPORT based on the value of the
   Depth request header.





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7.3.  Date and floating time

   iCalendar provides a way to specify DATE and DATE-TIME values that
   are not bound to any time zone in particular, hereafter called
   "floating date" and "floating time" respectively.  These values are
   used to represent the same day, hour, minute and second value
   regardless of which time zone is being observed.  For instance, the
   DATE value "20051111", represents November 11th, 2005 in no specific
   time zone, while the DATE-TIME value "20051111T111100" represents
   November 11th, 2005 at 11:11 AM in no specific time zone.

   CalDAV servers may need to convert "floating date" and "floating
   time" values in date with UTC time values in the processing of
   calendaring REPORT requests.

   For the CALDAV:calendar-query REPORT, CalDAV servers MUST rely on the
   value of the CALDAV:timezone XML element, if specified as part of the
   request body, to perform the proper conversion of "floating date" and
   "floating time" values to date with UTC time values.  If the CALDAV:
   timezone XML element is not specified in the request body, CalDAV
   servers MUST rely on the value of the CALDAV:calendar-timezone
   property, if defined, else the CalDAV servers MAY rely on the time
   zone of their choice.

   For the CALDAV:free-busy-query REPORT, CalDAV servers MUST rely on
   the value of the CALDAV:calendar-timezone property, if defined, to
   compute the proper FREEBUSY time period value as date with UTC time,
   for calendar components scheduled with "floating date" or "floating
   time".  If the CALDAV:calendar-timezone property is not defined,
   CalDAV servers MAY rely on the time zone of their choice.

7.4.  Time range filtering

   Some of the reports defined in this section can include a time range
   filter that is used to restrict the set of calendar object resources
   returned to just those that overlap the specified time range.  The
   time range filter can be applied to a calendar component as a whole,
   or to specific calendar component properties with date or date-time
   value types.

   To determine whether a calendar object resource matches the time
   range filter element, the start and end times for the targeted
   component or property are determined and then compared to the
   requested time range.  If there is an overlap with the requested time
   range, then the calendar object resource matches the filter element.
   The rules defined in [RFC2445] for determining the actual start and
   end times of calendar components MUST be used, and these are fully
   enumerated in Section 9.9 of this document.



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   When such time range filtering is used, special consideration must be
   given to recurring calendar components such as VEVENT and VTODO
   components.  The server MUST expand recurring components to determine
   whether any recurrence instances overlap the specified time range.
   If one or more recurrence instances overlap the time range, then the
   calendar object resource matches the filter element.

7.5.  Searching Text: Collations

   Some of the reports defined in this section do text matches of
   character strings provided by the client and compared to stored
   calendar data.  Since iCalendar data is by default encoded in the
   UTF-8 charset and may include characters outside of the US-ASCII
   charset range in some property and parameter values, there is a need
   to ensure that text matching follows well-defined rules.

   To deal with this, this specification makes use of the IANA Collation
   Registry defined in [I-D.newman-i18n-comparator] to specify
   collations that may be used to carry out the text comparison
   operations with a well-defined rule.

   The comparisons used in CalDAV are all "substring" matches as per
   [I-D.newman-i18n-comparator] Section 4.2.  Collations supported by
   the server MUST support "substring" match operations.

   CalDAV servers are REQUIRED to support the "i;ascii-casemap" and
   "i;octet" collations as described in [I-D.newman-i18n-comparator],
   and MAY support other collations.

   Servers MUST advertise the set of collations that they support via
   the CALDAV:supported-collation-set property defined on any resource
   that supports reports that use collations.

   Clients MUST only use collations from the list advertised by the
   server.

   In the absence of a collation explicitly specified by the client, or
   if the client specifies the "default" collation identifier (as
   defined in [I-D.newman-i18n-comparator] Section 3.1), the server MUST
   default to using "i;ascii-casemap" as the collation.

   Wildcards (as defined in [I-D.newman-i18n-comparator] Section 3.2)
   MUST NOT be used in the collation identifier.

   If the client chooses a collation not supported by the server, the
   server MUST respond with a CALDAV:supported-collation precondition
   error response.




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7.5.1.  CALDAV:supported-collation-set Property

   Name: supported-collation-set

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

   Purpose: Identifies the set of collations supported by the server for
      text matching operations.

   Conformance: This property MUST be defined on any resource that
      supports a REPORT that does text matching.  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-collation-set property contains
      zero or more CALDAV:supported-collation elements which specify the
      collection identifiers of the collations supported by the server.

   Definition:

         <!ELEMENT supported-collation-set (supported-collation*)>
           <!ELEMENT supported-collation (#PCDATA)>

   Example:

       <C:supported-collation-set
           xmlns:C="urn:ietf:params:xml:ns:caldav">
         <C:supported-collation>i;ascii-casemap</C:supported-collation>
         <C:supported-collation>i;octet</C:supported-collation>
       </C:supported-collation-set>

7.6.  Partial Retrieval

   Some calendaring REPORTs defined in this document allow partial
   retrieval of calendar object resources.  A CalDAV client can specify
   what information to return in the body of a calendaring REPORT
   request.

   A CalDAV client can request particular WebDAV property values, all
   WebDAV property values, or a list of the names of the resource's
   WebDAV properties.  A CalDAV client can also request calendar data to
   be returned and whether all calendar components and properties should
   be returned or only particular ones.  See CALDAV:calendar-data in
   Section 9.6.

   By default, the returned calendar data will include the component
   that defines the recurrence set, referred to as the "master
   component", as well as the components that define exceptions to the



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   recurrence set, referred to as the "overridden components".

   A CalDAV client only interested in the recurrence instances that
   overlap a specified time range can request to receive only the
   "master component" along with the "overridden components" that impact
   the specified time range and thus limit the data returned by the
   server.  See CALDAV:limit-recurrence-set in Section 9.6.6.  An
   overridden component impacts a time range if its current start and
   end times overlap the time range, or if the original start and end
   times - the ones that would have been used if the instance were not
   overridden - overlap the time range.

   A CalDAV client with no support for recurrence properties (i.e.,
   EXDATE, EXRULE, RDATE and RRULE) and possibly VTIMEZONE components,
   or a client not willing to perform recurrence expansion because of
   limited processing capability can request to receive only the
   recurrence instances that overlap a specified time range as separate
   calendar components that each define exactly one recurrence instance.
   See CALDAV:expand in Section 9.6.5.

   Finally, in the case of VFREEBUSY components, a CalDAV client can
   request to receive only the FREEBUSY property values that overlap a
   specified time range.  See CALDAV:limit-freebusy-set in
   Section 9.6.7.

7.7.  Non-standard components, properties and parameters

   Servers MUST support the use of non-standard component, property or
   parameter names in the CALDAV:calendar-data XML element in
   calendaring REPORT requests to allow clients to request that non-
   standard components, properties and parameters be returned in the
   calendar data provided in the response.

   Servers MAY support the use of non-standard component, property or
   parameter names in the CALDAV:comp-filter, CALDAV:prop-filter and
   CALDAV:param-filter XML elements specified in the CALDAV:filter XML
   element of calendaring REPORT requests.

   Servers MUST fail with the CALDAV:supported-filter precondition if a
   calendaring REPORT request uses a CALDAV:comp-filter, CALDAV:prop-
   filter or CALDAV:param-filter XML element that makes reference to a
   non-standard component, property or parameter name which the server
   does not support queries on.

7.8.  CALDAV:calendar-query Report

   The CALDAV:calendar-query REPORT performs a search for all calendar
   object resources that match a specified filter.  The response of this



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   REPORT will contain all the WebDAV properties and calendar object
   resource data specified in the request.  In the case of the CALDAV:
   calendar-data XML element, one can explicitly specify the calendar
   components and properties that should be returned in the calendar
   object resource data that matches the filter.

   The format of this REPORT is modeled on the PROPFIND method.  The
   request and response bodies of the CALDAV:calendar-query REPORT use
   XML elements that are also used by PROPFIND.  In particular the
   request can include XML elements to request WebDAV properties to be
   returned.  When that occurs the response should follow the same
   behavior as PROPFIND with respect to the DAV:multistatus response
   elements used to return specific property results.  For instance, a
   request to retrieve the value of a property which does not exist is
   an error and MUST be noted with a response XML element which contains
   a 404 (Not Found) status value.

   Support for the CALDAV:calendar-query REPORT is REQUIRED.

   Marshalling:

      The request body MUST be a CALDAV:calendar-query XML element as
      defined in Section 9.5.

      The request MAY include a Depth header.  If no Depth header is
      included, Depth:0 is assumed.

      The response body for a successful request MUST be a DAV:
      multistatus XML element (i.e., the response uses the same format
      as the response for PROPFIND).  In the case where there are no
      response elements, the returned DAV:multistatus XML element is
      empty.

      The response body for a successful CALDAV:calendar-query REPORT
      request MUST contain a DAV:response element for each iCalendar
      object that matched the search filter.  Calendar data is being
      returned in the CALDAV:calendar-data XML element inside the DAV:
      propstat XML element.

   Preconditions:

      (CALDAV:supported-calendar-data): The attributes "content-type"
      and "version" of the CALDAV:calendar-data XML element (see
      Section 9.6) specify a media type supported by the server for
      calendar object resources.

      (CALDAV:valid-filter): The CALDAV:filter XML element (see
      Section 9.7) specified in the REPORT request MUST be valid.  For



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      instance, a CALDAV:filter cannot nest a <C:comp name="VEVENT">
      element in a <C:comp name="VTODO"> element, or a CALDAV:filter
      cannot nest a <C:time-range start="..." end="..."> element in a
      <C:prop name="SUMMARY"> element.

      (CALDAV:supported-filter): The CALDAV:comp-filter (see
      Section 9.7.1), CALDAV:prop-filter (see Section 9.7.2) and CALDAV:
      param-filter (see Section 9.7.3) XML elements used in the CALDAV:
      filter XML element (see Section 9.7) in the REPORT request only
      make reference to components, properties and parameters for which
      queries are supported by the server. i.e., if the CALDAV:filter
      element attempts to reference an unsupported component, property
      or parameter, this precondition is violated.  Servers SHOULD
      report the CALDAV:comp-filter, CALDAV:prop-filter or CALDAV:param-
      filter for which it does not provide support.

            <!ELEMENT supported-filter (comp-filter*,
                                        prop-filter*,
                                        param-filter*)>

      (CALDAV:valid-calendar-data): The time zone specified in the
      REPORT request MUST be a valid iCalendar object containing a
      single valid VTIMEZONE component.

      (CALDAV:min-date-time): Any XML element specifying a range of time
      MUST have its start or end date or time values greater than or
      equal to the value of the CALDAV:min-date-time property value
      (Section 5.2.6) on the calendar collections being targeted by the
      REPORT;

      (CALDAV:max-date-time): Any XML element specifying a range of time
      MUST have its start or end date or time values less than or equal
      to the value of the CALDAV:max-date-time property value
      (Section 5.2.7) on the calendar collections being targeted by the
      REPORT;

      (CALDAV:supported-collation): Any XML attribute specifying a
      collation MUST specify a collation supported by the server as
      described in Section 7.5.

   Postconditions:

      (DAV:number-of-matches-within-limits): The number of matching
      calendar object resources must fall within server-specific,
      predefined limits.  For example, this condition might be triggered
      if a search specification would cause the return of an extremely
      large number of responses.




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7.8.1.  Example: Partial retrieval of events by time range

   In this example, the client requests the server to return specific
   components and properties of the VEVENT components that overlap the
   time range from January 4th, 2006 at 00:00:00 AM UTC to January 5th,
   2006 at 00:00:00 AM UTC.  In addition the DAV:getetag property is
   also requested and returned as part of the response.  Note that the
   first calendar object returned is a recurring event whose first
   instance lies outside of the requested time range, but whose third
   instance does overlap the time range.  Note that due to the CALDAV:
   calendar-data element restrictions, the DTSTAMP property in VEVENT
   components has not been returned, and the only property returned in
   the VCALENDAR object is VERSION.

   See Appendix B for the calendar data being targeted by this example.




































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   >> Request <<

   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/>
       <C:calendar-data>
         <C:comp name="VCALENDAR">
           <C:prop name="VERSION"/>
           <C:comp name="VEVENT">
             <C:prop name="SUMMARY"/>
             <C:prop name="UID"/>
             <C:prop name="DTSTART"/>
             <C:prop name="DTEND"/>
             <C:prop name="DURATION"/>
             <C:prop name="RRULE"/>
             <C:prop name="RDATE"/>
             <C:prop name="EXRULE"/>
             <C:prop name="EXDATE"/>
             <C:prop name="RECURRENCE-ID"/>
           </C:comp>
           <C:comp name="VTIMEZONE"/>
         </C:comp>
       </C:calendar-data>
     </D:prop>
     <C:filter>
       <C:comp-filter name="VCALENDAR">
         <C:comp-filter name="VEVENT">
           <C:time-range start="20060104T000000Z"
                         end="20060105T000000Z"/>
         </C:comp-filter>
       </C:comp-filter>
     </C:filter>
   </C:calendar-query>

   >> Response <<

   HTTP/1.1 207 Multi-Status
   Date: Fri, 11 Nov 2005 09:32:12 GMT
   Content-Type: application/xml; charset="utf-8"
   Content-Length: xxxx



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   <?xml version="1.0" encoding="utf-8" ?>
   <D:multistatus xmlns:D="DAV:"
              xmlns:C="urn:ietf:params:xml:ns:caldav">
     <D:response>
       <D:href>http://cal.example.com/bernard/work/abcd2.ics</D:href>
       <D:propstat>
         <D:prop>
           <D:getetag>"fffff-abcd2"</D:getetag>
           <C:calendar-data>BEGIN:VCALENDAR
   VERSION:2.0
   BEGIN:VTIMEZONE
   LAST-MODIFIED:20040110T032845Z
   TZID:US/Eastern
   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
   DTSTART;TZID=US/Eastern:20060102T120000
   DURATION:PT1H
   RRULE:FREQ=DAILY;COUNT=5
   SUMMARY:Event #2
   UID:00959BC664CA650E933C892C@example.com
   END:VEVENT
   BEGIN:VEVENT
   DTSTART;TZID=US/Eastern:20060104T140000
   DURATION:PT1H
   RECURRENCE-ID;TZID=US/Eastern:20060104T120000
   SUMMARY:Event #2 bis
   UID:00959BC664CA650E933C892C@example.com
   END:VEVENT
   BEGIN:VEVENT
   DTSTART;TZID=US/Eastern:20060106T140000
   DURATION:PT1H
   RECURRENCE-ID;TZID=US/Eastern:20060106T120000
   SUMMARY:Event #2 bis bis
   UID:00959BC664CA650E933C892C@example.com



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   END:VEVENT
   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/bernard/work/abcd3.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:VTIMEZONE
   LAST-MODIFIED:20040110T032845Z
   TZID:US/Eastern
   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
   DTSTART;TZID=US/Eastern:20060104T100000
   DURATION:PT1H
   SUMMARY:Event #3
   UID:DC6C50A017428C5216A2F1CD@example.com
   END:VEVENT
   END:VCALENDAR
   </C:calendar-data>
         </D:prop>
         <D:status>HTTP/1.1 200 OK</D:status>
       </D:propstat>
     </D:response>
   </D:multistatus>





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7.8.2.  Example: Partial retrieval of recurring events

   In this example, the client requests the server to return VEVENT
   components that overlap the time range from January 3rd, 2006 at 00:
   00:00 AM UTC to January 5th, 2006 at 00:00:00 AM UTC.  Use of the
   CALDAV:limit-recurrence-set element causes the server to only return
   overridden recurrence components that overlap the time range
   specified in that element, or that affect other instances that
   overlap the time range (e.g., in the case of a "THISANDFUTURE"
   behavior).  In this example the first overridden component in the
   matching resource is returned but the second one is not.

   See Appendix B for the calendar data being targeted by this example.

   >> Request <<

   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>
       <C:calendar-data>
         <C:limit-recurrence-set start="20060103T000000Z"
                                 end="20060105T000000Z"/>
       </C:calendar-data>
     </D:prop>
     <C:filter>
       <C:comp-filter name="VCALENDAR">
         <C:comp-filter name="VEVENT">
           <C:time-range start="20060103T000000Z"
                         end="20060105T000000Z"/>
         </C:comp-filter>
       </C:comp-filter>
     </C:filter>
   </C:calendar-query>

   >> Response <<

   HTTP/1.1 207 Multi-Status
   Date: Fri, 11 Nov 2006 09:32:12 GMT
   Content-Type: application/xml; charset="utf-8"
   Content-Length: xxxx




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   <?xml version="1.0" encoding="utf-8" ?>
   <D:multistatus xmlns:D="DAV:"
              xmlns:C="urn:ietf:params:xml:ns:caldav">
     <D:response>
       <D:href>http://cal.example.com/bernard/work/abcd2.ics</D:href>
       <D:propstat>
         <D:prop>
           <D:getetag>"fffff-abcd2"</D:getetag>
           <C:calendar-data>BEGIN:VCALENDAR
   VERSION:2.0
   PRODID:-//Example Corp.//CalDAV Client//EN
   BEGIN:VTIMEZONE
   LAST-MODIFIED:20040110T032845Z
   TZID:US/Eastern
   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:20060206T001121Z
   DTSTART;TZID=US/Eastern:20060102T120000
   DURATION:PT1H
   RRULE:FREQ=DAILY;COUNT=5
   SUMMARY:Event #2
   UID:00959BC664CA650E933C892C@example.com
   END:VEVENT
   BEGIN:VEVENT
   DTSTAMP:20060206T001121Z
   DTSTART;TZID=US/Eastern:20060104T140000
   DURATION:PT1H
   RECURRENCE-ID;TZID=US/Eastern:20060104T120000
   SUMMARY:Event #2 bis
   UID:00959BC664CA650E933C892C@example.com
   END:VEVENT
   END:VCALENDAR
   </C:calendar-data>
         </D:prop>



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         <D:status>HTTP/1.1 200 OK</D:status>
       </D:propstat>
     </D:response>
     <D:response>
       <D:href>http://cal.example.com/bernard/work/abcd3.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:VTIMEZONE
   LAST-MODIFIED:20040110T032845Z
   TZID:US/Eastern
   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
   ATTENDEE;PARTSTAT=ACCEPTED;ROLE=CHAIR:mailto:cyrus@example.com
   ATTENDEE;PARTSTAT=NEEDS-ACTION:mailto:lisa@example.com
   DTSTAMP:20060206T001220Z
   DTSTART;TZID=US/Eastern:20060104T100000
   DURATION:PT1H
   LAST-MODIFIED:20060206T001330Z
   ORGANIZER:mailto:cyrus@example.com
   SEQUENCE:1
   STATUS:TENTATIVE
   SUMMARY:Event #3
   UID:DC6C50A017428C5216A2F1CD@example.com
   X-ABC-GUID:E1CX5Dr-0007ym-Hz@example.com
   END:VEVENT
   END:VCALENDAR
   </C:calendar-data>
         </D:prop>
         <D:status>HTTP/1.1 200 OK</D:status>
       </D:propstat>



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     </D:response>
   </D:multistatus>

7.8.3.  Example: Expanded retrieval of recurring events

   In this example, the client requests the server to return VEVENT
   components that overlap the time range from January 2nd, 2006 at 00:
   00:00 AM UTC to January 5th, 2006 at 00:00:00 AM UTC and to return
   recurring calendar components expanded into individual recurrence
   instance calendar components.  Use of the CALDAV:expand element
   causes the server to only return overridden recurrence instances that
   overlap the time range specified in that element.

   See Appendix B for the calendar data being targeted by this example.

   >> Request <<

   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>
       <C:calendar-data>
         <C:expand start="20060103T000000Z"
                   end="20060105T000000Z"/>
       </C:calendar-data>
     </D:prop>
     <C:filter>
       <C:comp-filter name="VCALENDAR">
         <C:comp-filter name="VEVENT">
           <C:time-range start="20060103T000000Z"
                         end="20060105T000000Z"/>
         </C:comp-filter>
       </C:comp-filter>
     </C:filter>
   </C:calendar-query>

   >> Response <<

   HTTP/1.1 207 Multi-Status
   Date: Fri, 11 Nov 2006 09:32:12 GMT
   Content-Type: application/xml; charset="utf-8"
   Content-Length: xxxx



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   <?xml version="1.0" encoding="utf-8" ?>
   <D:multistatus xmlns:D="DAV:"
              xmlns:C="urn:ietf:params:xml:ns:caldav">
     <D:response>
       <D:href>http://cal.example.com/bernard/work/abcd2.ics</D:href>
       <D:propstat>
         <D:prop>
           <D:getetag>"fffff-abcd2"</D:getetag>
           <C:calendar-data>BEGIN:VCALENDAR
   VERSION:2.0
   PRODID:-//Example Corp.//CalDAV Client//EN
   BEGIN:VEVENT
   DTSTAMP:20060206T001121Z
   DTSTART:20060103T170000
   DURATION:PT1H
   RECURRENCE-ID:20060103T170000
   SUMMARY:Event #2
   UID:00959BC664CA650E933C892C@example.com
   END:VEVENT
   BEGIN:VEVENT
   DTSTAMP:20060206T001121Z
   DTSTART:20060104T190000
   DURATION:PT1H
   RECURRENCE-ID:20060104T170000
   SUMMARY:Event #2 bis
   UID:00959BC664CA650E933C892C@example.com
   END:VEVENT
   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/bernard/work/abcd3.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:VEVENT
   ATTENDEE;PARTSTAT=ACCEPTED;ROLE=CHAIR:mailto:cyrus@example.com
   ATTENDEE;PARTSTAT=NEEDS-ACTION:mailto:lisa@example.com
   DTSTAMP:20060206T001220Z
   DTSTART:20060104T150000
   DURATION:PT1H
   LAST-MODIFIED:20060206T001330Z



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   ORGANIZER:mailto:cyrus@example.com
   SEQUENCE:1
   STATUS:TENTATIVE
   SUMMARY:Event #3
   UID:DC6C50A017428C5216A2F1CD@example.com
   X-ABC-GUID:E1CX5Dr-0007ym-Hz@example.com
   END:VEVENT
   END:VCALENDAR
   </C:calendar-data>
         </D:prop>
         <D:status>HTTP/1.1 200 OK</D:status>
       </D:propstat>
     </D:response>
   </D:multistatus>

7.8.4.  Example: Partial retrieval of stored free busy components

   In this example, the client requests the server to return the
   VFREEBUSY components that have free busy information that overlap the
   time range from January 2nd, 2006 at 00:00:00 AM UTC (inclusively) to
   January 3rd, 2006 at 00:00:00 AM UTC (exclusively).  Use of the
   CALDAV:limit-freebusy-set element causes the server to only return
   the FREEBUSY property values that overlap the time range specified in
   that element.  Note that this is not an example of discovering when
   the calendar owner is busy.

   See Appendix B for the calendar data being targeted by this example.
























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   >> Request <<

   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>
       <C:calendar-data>
         <C:limit-freebusy-set start="20060102T000000Z"
                                 end="20060103T000000Z"/>
       </C:calendar-data>
     </D:prop>
     <C:filter>
       <C:comp-filter name="VCALENDAR">
         <C:comp-filter name="VFREEBUSY">
           <C:time-range start="20060102T000000Z"
                           end="20060103T000000Z"/>
         </C:comp-filter>
       </C:comp-filter>
     </C:filter>
   </C:calendar-query>

























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   >> Response <<

   HTTP/1.1 207 Multi-Status
   Date: Fri, 11 Nov 2006 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/bernard/work/abcd8.ics</D:href>
       <D:propstat>
         <D:prop>
           <D:getetag>"fffff-abcd8"</D:getetag>
           <C:calendar-data>BEGIN:VCALENDAR
   VERSION:2.0
   PRODID:-//Example Corp.//CalDAV Client//EN
   BEGIN:VFREEBUSY
   ORGANIZER;CN="Bernard Desruisseaux":mailto:bernard@example.com
   UID:76ef34-54a3d2@example.com
   DTSTAMP:20050530T123421Z
   DTSTART:20060101T100000Z
   DTEND:20060108T100000Z
   FREEBUSY;FBTYPE=BUSY-TENTATIVE:20060102T100000Z/20060102T120000Z
   END:VFREEBUSY
   END:VCALENDAR
   </C:calendar-data>
         </D:prop>
         <D:status>HTTP/1.1 200 OK</D:status>
       </D:propstat>
     </D:response>
   </D:multistatus>

7.8.5.  Example: Retrieval of to-dos by alarm time range

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

   See Appendix B for the calendar data being targeted by this example.










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   >> Request <<

   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:C="urn:ietf:params:xml:ns:caldav">
     <D:prop xmlns:D="DAV:">
       <D:getetag/>
       <C:calendar-data/>
     </D:prop>
     <C:filter>
       <C:comp-filter name="VCALENDAR">
         <C:comp-filter name="VTODO">
           <C:comp-filter name="VALARM">
             <C:time-range start="20060106T100000Z"
                             end="20060107T100000Z"/>
           </C:comp-filter>
         </C:comp-filter>
       </C:comp-filter>
     </C:filter>
   </C:calendar-query>


























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   >> Response <<

   HTTP/1.1 207 Multi-Status
   Date: Fri, 11 Nov 2006 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/bernard/work/abcd4.ics</D:href>
       <D:propstat>
         <D:prop>
           <D:getetag>"fffff-abcd4"</D:getetag>
           <C:calendar-data>BEGIN:VCALENDAR
   VERSION:2.0
   PRODID:-//Example Corp.//CalDAV Client//EN
   BEGIN:VTODO
   DTSTAMP:20060205T235300Z
   DUE;TZID=US/Eastern:20060106T120000
   LAST-MODIFIED:20060205T235308Z
   SEQUENCE:1
   STATUS:NEEDS-ACTION
   SUMMARY:Task #2
   UID:E10BA47467C5C69BB74E8720@example.com
   BEGIN:VALARM
   ACTION:AUDIO
   TRIGGER;RELATED=START:-PT10M
   END:VALARM
   END:VTODO
   END:VCALENDAR
   </C:calendar-data>
         </D:prop>
         <D:status>HTTP/1.1 200 OK</D:status>
       </D:propstat>
     </D:response>
   </D:multistatus>

7.8.6.  Example: Retrieval of event by UID

   In this example, the client requests the server to return the VEVENT
   component that has the UID property set to
   "DC6C50A017428C5216A2F1CD@example.com".

   See Appendix B for the calendar data being targeted by this example.





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   >> Request <<

   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:C="urn:ietf:params:xml:ns:caldav">
     <D:prop xmlns:D="DAV:">
       <D:getetag/>
       <C:calendar-data/>
     </D:prop>
     <C:filter>
       <C:comp-filter name="VCALENDAR">
         <C:comp-filter name="VEVENT">
           <C:prop-filter name="UID">
             <C:text-match collation="i;octet"
             >DC6C50A017428C5216A2F1CD@example.com</C:text-match>
           </C:prop-filter>
         </C:comp-filter>
       </C:comp-filter>
     </C:filter>
   </C:calendar-query>

   >> Response <<

   HTTP/1.1 207 Multi-Status
   Date: Fri, 11 Nov 2006 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/bernard/work/abcd3.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:VTIMEZONE
   LAST-MODIFIED:20040110T032845Z
   TZID:US/Eastern
   BEGIN:DAYLIGHT



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   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
   ATTENDEE;PARTSTAT=ACCEPTED;ROLE=CHAIR:mailto:cyrus@example.com
   ATTENDEE;PARTSTAT=NEEDS-ACTION:mailto:lisa@example.com
   DTSTAMP:20060206T001220Z
   DTSTART;TZID=US/Eastern:20060104T100000
   DURATION:PT1H
   LAST-MODIFIED:20060206T001330Z
   ORGANIZER:mailto:cyrus@example.com
   SEQUENCE:1
   STATUS:TENTATIVE
   SUMMARY:Event #3
   UID:DC6C50A017428C5216A2F1CD@example.com
   X-ABC-GUID:E1CX5Dr-0007ym-Hz@example.com
   END:VEVENT
   END:VCALENDAR
   </C:calendar-data>
         </D:prop>
         <D:status>HTTP/1.1 200 OK</D:status>
       </D:propstat>
     </D:response>
   </D:multistatus>

7.8.7.  Example: Retrieval of events by PARTSTAT

   In this example, the client requests the server to return the VEVENT
   components that have the ATTENDEE property with the value
   "mailto:lisa@example.com" and for which the PARTSTAT parameter is set
   to "NEEDS-ACTION".

   See Appendix B for the calendar data being targeted by this example.







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   >> Request <<

   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:C="urn:ietf:params:xml:ns:caldav">
     <D:prop xmlns:D="DAV:">
       <D:getetag/>
       <C:calendar-data/>
     </D:prop>
     <C:filter>
       <C:comp-filter name="VCALENDAR">
         <C:comp-filter name="VEVENT">
           <C:prop-filter name="ATTENDEE">
             <C:text-match collation="i;ascii-casemap"
              >mailto:lisa@example.com</C:text-match>
             <C:param-filter name="PARTSTAT">
               <C:text-match collation="i;ascii-casemap"
                >NEEDS-ACTION</C:text-match>
             </C:param-filter>
           </C:prop-filter>
         </C:comp-filter>
       </C:comp-filter>
     </C:filter>
   </C:calendar-query>

   >> Response <<

   HTTP/1.1 207 Multi-Status
   Date: Fri, 11 Nov 2006 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/bernard/work/abcd3.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



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   BEGIN:VTIMEZONE
   LAST-MODIFIED:20040110T032845Z
   TZID:US/Eastern
   BEGIN:DAYLIGHT
   DTSTART:20000404T020000
   RRULE:FREQ=YEARLY;BYDAY=1SU;BYMONTH=4
   TZNAME:EDT
   TZOFFSETFROM:-0500
   TZOFF