GENWiki

Premier IT Outsourcing and Support Services within the UK

User Tools

Site Tools


rfc:rfc4791

Network Working Group C. Daboo Request for Comments: 4791 Apple Category: Standards Track B. Desruisseaux

                                                                Oracle
                                                          L. Dusseault
                                                           CommerceNet
                                                            March 2007
             Calendaring Extensions to WebDAV (CalDAV)

Status of This Memo

 This document specifies an Internet standards track protocol for the
 Internet community, and requests discussion and suggestions for
 improvements.  Please refer to the current edition of the "Internet
 Official Protocol Standards" (STD 1) for the standardization state
 and status of this protocol.  Distribution of this memo is unlimited.

Copyright Notice

 Copyright (C) The IETF Trust (2007).

Abstract

 This document defines extensions to the Web Distributed Authoring and
 Versioning (WebDAV) protocol to specify a standard way of accessing,
 managing, and sharing calendaring and scheduling information based on
 the iCalendar format.  This document defines the "calendar-access"
 feature of CalDAV.

Daboo, et al. Standards Track [Page 1] RFC 4791 CalDAV March 2007

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  . . . . . . . . . . . . 19
     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
   7.4.  Time Range Filtering . . . . . . . . . . . . . . . . . . . 32
   7.5.  Searching Text: Collations . . . . . . . . . . . . . . . . 33

Daboo, et al. Standards Track [Page 2] RFC 4791 CalDAV March 2007

     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 . . . . . . . . . . . . . . . 36
     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 . . . . . . . . . . . . . . . . . . . . . . 48
     7.8.5.  Example: Retrieval of To-Dos by Alarm Time Range . . . 50
     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 . . . . . . . . . . . . . . . . . . . . . . . . . . 69
   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  . . . . . . . . . . . . 70
       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 . . . . . . . . . . 78
   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 . . . . . . . . . . . . . . 81
     9.6.3.  CALDAV:allprop XML Element . . . . . . . . . . . . . . 81
     9.6.4.  CALDAV:prop XML Element  . . . . . . . . . . . . . . . 82
     9.6.5.  CALDAV:expand XML Element  . . . . . . . . . . . . . . 82
     9.6.6.  CALDAV:limit-recurrence-set XML Element  . . . . . . . 83
     9.6.7.  CALDAV:limit-freebusy-set XML Element  . . . . . . . . 84
   9.7.  CALDAV:filter XML Element  . . . . . . . . . . . . . . . . 85

Daboo, et al. Standards Track [Page 3] RFC 4791 CalDAV March 2007

     9.7.1.  CALDAV:comp-filter XML Element . . . . . . . . . . . . 85
     9.7.2.  CALDAV:prop-filter XML Element . . . . . . . . . . . . 86
     9.7.3.  CALDAV:param-filter XML Element  . . . . . . . . . . . 87
     9.7.4.  CALDAV:is-not-defined XML Element  . . . . . . . . . . 88
     9.7.5.  CALDAV:text-match XML Element  . . . . . . . . . . . . 88
   9.8.  CALDAV:timezone XML Element  . . . . . . . . . . . . . . . 89
   9.9.  CALDAV:time-range XML Element  . . . . . . . . . . . . . . 90
   9.10. CALDAV:calendar-multiget XML Element . . . . . . . . . . . 94
   9.11. CALDAV:free-busy-query XML Element . . . . . . . . . . . . 95
 10. Internationalization Considerations  . . . . . . . . . . . . . 95
 11. Security Considerations  . . . . . . . . . . . . . . . . . . . 95
 12. IANA Considerations  . . . . . . . . . . . . . . . . . . . . . 96
   12.1. Namespace Registration . . . . . . . . . . . . . . . . . . 96
 13. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 96
 14. References . . . . . . . . . . . . . . . . . . . . . . . . . . 97
   14.1. Normative References . . . . . . . . . . . . . . . . . . . 97
   14.2. Informative References . . . . . . . . . . . . . . . . . . 98
 Appendix A.  CalDAV Method Privilege Table (Normative) . . . . . . 99
 Appendix B.  Calendar Collections Used in the Examples . . . . . . 99

Daboo, et al. Standards Track [Page 4] RFC 4791 CalDAV March 2007

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 types.  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.

Daboo, et al. Standards Track [Page 5] RFC 4791 CalDAV March 2007

 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 Appendix 3 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 either be 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 the calendar
    object resource format;
 o  MUST support WebDAV Class 1 [RFC2518] (note that [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]);
 o  MUST support ETags [RFC2616] with additional requirements
    specified in Section 5.3.4 of this document;

Daboo, et al. Standards Track [Page 6] RFC 4791 CalDAV March 2007

 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 that 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, to-do, 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
 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

Daboo, et al. Standards Track [Page 7] RFC 4791 CalDAV March 2007

 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.
 Therefore, 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 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.

Daboo, et al. Standards Track [Page 8] RFC 4791 CalDAV March 2007

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 one VEVENT component 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 that 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).

Daboo, et al. Standards Track [Page 9] RFC 4791 CalDAV March 2007

 For example, given the following iCalendar object:
 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>

Daboo, et al. Standards Track [Page 10] RFC 4791 CalDAV March 2007

 A calendar collection can be created through provisioning (i.e.,
 automatically created when a user's account is provisioned), or it
 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 rooms).  However, note that this document doesn't
 define the purpose of extra calendar collections.  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.

Daboo, et al. Standards Track [Page 11] RFC 4791 CalDAV March 2007

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, access-control, calendar-access
 Date: Sat, 11 Nov 2006 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, method,
 or privilege defined in this specification.

5.2. Calendar Collection Properties

 This section defines properties for 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.

Daboo, et al. Standards Track [Page 12] RFC 4791 CalDAV March 2007

 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.

Daboo, et al. Standards Track [Page 13] RFC 4791 CalDAV March 2007

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

Daboo, et al. Standards Track [Page 14] RFC 4791 CalDAV March 2007

 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
    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 all component types are accepted.
 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

Daboo, et al. Standards Track [Page 15] RFC 4791 CalDAV March 2007

    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 "text/calendar" and iCalendar version 2.0, and clients can
    assume that the server will only accept this data.
 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 a
    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)

Daboo, et al. Standards Track [Page 16] RFC 4791 CalDAV March 2007

 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
    DATE-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 DATE-TIME value in a calendar object resource
    stored in a calendar collection.  Any attempt to store a calendar
    object resource using a DATE or DATE-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>

Daboo, et al. Standards Track [Page 17] RFC 4791 CalDAV March 2007

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
    DATE-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 DATE-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>

Daboo, et al. Standards Track [Page 18] RFC 4791 CalDAV March 2007

5.2.8. CALDAV:max-instances Property

 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

Daboo, et al. Standards Track [Page 19] RFC 4791 CalDAV March 2007

    returned by a PROPFIND DAV:allprop request (as defined in Section
    12.14.1 of [RFC2518]).
 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

 Calendar collections and calendar object resources may be created by
 either a CalDAV client or by the CalDAV server.  This specification
 defines restrictions and a data model that both clients and servers
 MUST adhere to when manipulating such calendar data.

5.3.1. MKCALENDAR Method

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

Daboo, et al. Standards Track [Page 20] RFC 4791 CalDAV March 2007

 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 help organize their data better.
 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:
    (DAV:resource-must-be-null): A resource MUST NOT exist at the
    Request-URI;

Daboo, et al. Standards Track [Page 21] RFC 4791 CalDAV March 2007

    (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;
       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

Daboo, et al. Standards Track [Page 22] RFC 4791 CalDAV March 2007

       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.

Daboo, et al. Standards Track [Page 23] RFC 4791 CalDAV March 2007

 >> 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>

Daboo, et al. Standards Track [Page 24] RFC 4791 CalDAV March 2007

 >> Response <<
 HTTP/1.1 201 Created
 Cache-Control: no-cache
 Date: Sat, 11 Nov 2006 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.

Daboo, et al. Standards Track [Page 25] RFC 4791 CalDAV March 2007

 >> 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: Sat, 11 Nov 2006 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, or when
 a COPY or MOVE operation of a calendar object resource into a
 calendar collection occurs, or when a COPY or MOVE operation occurs
 on a calendar collection.

Daboo, et al. Standards Track [Page 26] RFC 4791 CalDAV March 2007

 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 DATE-TIME property values (for each recurring

Daboo, et al. Standards Track [Page 27] RFC 4791 CalDAV March 2007

    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 DATE-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.

Daboo, et al. Standards Track [Page 28] RFC 4791 CalDAV March 2007

 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.

Daboo, et al. Standards Track [Page 29] RFC 4791 CalDAV March 2007

 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, access to GET, HEAD,
 OPTIONS, and PROPFIND on the resource is not implied (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 are either calendar
    collections or ordinary collections that have child or descendant
    calendar collections owned by the principal.
 Definition:
       <!ELEMENT calendar-home-set (DAV:href*)>

Daboo, et al. Standards Track [Page 30] RFC 4791 CalDAV March 2007

 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 request, based on the
 value of the Depth request header.

Daboo, et al. Standards Track [Page 31] RFC 4791 CalDAV March 2007

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 11, 2005 in no specific
 time zone, while the DATE-TIME value "20051111T111100" represents
 November 11, 2005, at 11:11 A.M. 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, or 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.

Daboo, et al. Standards Track [Page 32] RFC 4791 CalDAV March 2007

 When such time range filtering is used, special consideration must be
 given to recurring calendar components, such as VEVENT and VTODO.
 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 are compared to stored
 calendar data.  Since iCalendar data is, by default, encoded in the
 UTF-8 charset and may include characters outside 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 [RFC4790] 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
 [RFC4790], 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 [RFC4790], 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 [RFC4790], Section 3.1), the server MUST default to using
 "i;ascii-casemap" as the collation.
 Wildcards (as defined in [RFC4790], 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.

Daboo, et al. Standards Track [Page 33] RFC 4791 CalDAV March 2007

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 specify whether all calendar components and
 properties should be returned, or only particular ones.  See CALDAV:
 calendar-data in Section 9.6.

Daboo, et al. Standards Track [Page 34] RFC 4791 CalDAV March 2007

 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
 recurrence set, referred to as the "overridden components".
 A CalDAV client that is 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, or if it affects other
 instances that 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 unwilling 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 on which the
 server does not support queries.

Daboo, et al. Standards Track [Page 35] RFC 4791 CalDAV March 2007

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
 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 that does not exist is an
 error and MUST be noted with a response XML element that 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

Daboo, et al. Standards Track [Page 36] RFC 4791 CalDAV March 2007

    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
    instance, a CALDAV:filter cannot nest a <C:comp name="VEVENT">
    element in a <C:comp name="VTODO"> element, and 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 DATE-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 request;
    (CALDAV:max-date-time): Any XML element specifying a range of time
    MUST have its start or end DATE or DATE-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 request;
    (CALDAV:supported-collation): Any XML attribute specifying a
    collation MUST specify a collation supported by the server as
    described in Section 7.5.

Daboo, et al. Standards Track [Page 37] RFC 4791 CalDAV March 2007

 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.

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 4, 2006, at 00:00:00 A.M. UTC to January 5,
 2006, at 00:00:00 A.M. UTC.  In addition, the DAV:getetag property is
 also requested and returned as part of the response.  Note that the
 first calendar object returned is a recurring event whose first
 instance lies outside 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.

Daboo, et al. Standards Track [Page 38] RFC 4791 CalDAV March 2007

 >> 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: Sat, 11 Nov 2006 09:32:12 GMT
 Content-Type: application/xml; charset="utf-8"
 Content-Length: xxxx

Daboo, et al. Standards Track [Page 39] RFC 4791 CalDAV March 2007

 <?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

Daboo, et al. Standards Track [Page 40] RFC 4791 CalDAV March 2007

 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>

Daboo, et al. Standards Track [Page 41] RFC 4791 CalDAV March 2007

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 3, 2006, at 00:
 00:00 A.M. UTC to January 5, 2006, at 00:00:00 A.M. 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: Sat, 11 Nov 2006 09:32:12 GMT
 Content-Type: application/xml; charset="utf-8"
 Content-Length: xxxx

Daboo, et al. Standards Track [Page 42] RFC 4791 CalDAV March 2007

 <?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>

Daboo, et al. Standards Track [Page 43] RFC 4791 CalDAV March 2007

       <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>

Daboo, et al. Standards Track [Page 44] RFC 4791 CalDAV March 2007

   </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 2, 2006, at 00:
 00:00 A.M. UTC to January 5, 2006, at 00:00:00 A.M. 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: Sat, 11 Nov 2006 09:32:12 GMT
 Content-Type: application/xml; charset="utf-8"
 Content-Length: xxxx

Daboo, et al. Standards Track [Page 45] RFC 4791 CalDAV March 2007

 <?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

Daboo, et al. Standards Track [Page 46] RFC 4791 CalDAV March 2007

 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>

Daboo, et al. Standards Track [Page 47] RFC 4791 CalDAV March 2007

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 2, 2006, at 00:00:00 A.M. UTC (inclusively)
 to January 3, 2006, at 00:00:00 A.M. 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.
 >> 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>

Daboo, et al. Standards Track [Page 48] RFC 4791 CalDAV March 2007

 >> Response <<
 HTTP/1.1 207 Multi-Status
 Date: Sat, 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>

Daboo, et al. Standards Track [Page 49] RFC 4791 CalDAV March 2007

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.
 >> 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>

Daboo, et al. Standards Track [Page 50] RFC 4791 CalDAV March 2007

 >> Response <<
 HTTP/1.1 207 Multi-Status
 Date: Sat, 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.

Daboo, et al. Standards Track [Page 51] RFC 4791 CalDAV March 2007

 >> 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: Sat, 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

Daboo, et al. Standards Track [Page 52] RFC 4791 CalDAV March 2007

 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.

Daboo, et al. Standards Track [Page 53] RFC 4791 CalDAV March 2007

 >> 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: Sat, 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

Daboo, et al. Standards Track [Page 54] RFC 4791 CalDAV March 2007

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

7.8.8. Example: Retrieval of Events Only

 In this example, the client requests the server to return all VEVENT
 components.
 See Appendix B for the calendar data being targeted by this example.

Daboo, et al. Standards Track [Page 55] RFC 4791 CalDAV March 2007

 >> 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:comp-filter>
   </C:filter>
 </C:calendar-query>
 >> Response <<
 HTTP/1.1 207 Multi-Status
 Date: Sat, 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/abcd1.ics</D:href>
     <D:propstat>
       <D:prop>
         <D:getetag>"fffff-abcd1"</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

Daboo, et al. Standards Track [Page 56] RFC 4791 CalDAV March 2007

 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:20060206T001102Z
 DTSTART;TZID=US/Eastern:20060102T100000
 DURATION:PT1H
 SUMMARY:Event #1
 Description:Go Steelers!
 UID:74855313FA803DA593CD579A@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/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

Daboo, et al. Standards Track [Page 57] RFC 4791 CalDAV March 2007

 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
 BEGIN:VEVENT
 DTSTAMP:20060206T001121Z
 DTSTART;TZID=US/Eastern:20060106T140000
 DURATION:PT1H
 RECURRENCE-ID;TZID=US/Eastern:20060106T120000
 SUMMARY:Event #2 bis 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:VTIMEZONE
 LAST-MODIFIED:20040110T032845Z
 TZID:US/Eastern
 BEGIN:DAYLIGHT
 DTSTART:20000404T020000
 RRULE:FREQ=YEARLY;BYDAY=1SU;BYMONTH=4
 TZNAME:EDT
 TZOFFSETFROM:-0500
 TZOFFSETTO:-0400

Daboo, et al. Standards Track [Page 58] RFC 4791 CalDAV March 2007

 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>

7.8.9. Example: Retrieval of All Pending To-Dos

 In this example, the client requests the server to return all VTODO
 components that do not include a COMPLETED property and do not have a
 STATUS property value matching CANCELLED, i.e., VTODOs that still
 need to be worked on.
 See Appendix B for the calendar data being targeted by this example.

Daboo, et al. Standards Track [Page 59] RFC 4791 CalDAV March 2007

 >> 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:prop-filter name="COMPLETED">
           <C:is-not-defined/>
         </C:prop-filter>
         <C:prop-filter name="STATUS">
           <C:text-match
              negate-condition="yes">CANCELLED</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: Sat, 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

Daboo, et al. Standards Track [Page 60] RFC 4791 CalDAV March 2007

 DTSTAMP:20060205T235335Z
 DUE;VALUE=DATE:20060104
 STATUS:NEEDS-ACTION
 SUMMARY:Task #1
 UID:DDDEEB7915FA61233B861457@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:response>
     <D:href>http://cal.example.com/bernard/work/abcd5.ics</D:href>
     <D:propstat>
       <D:prop>
         <D:getetag>"fffff-abcd5"</D:getetag>
         <C:calendar-data>BEGIN:VCALENDAR
 VERSION:2.0
 PRODID:-//Example Corp.//CalDAV Client//EN
 BEGIN:VTODO
 DTSTAMP:20060205T235300Z
 DUE;VALUE=DATE:20060106
 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>

Daboo, et al. Standards Track [Page 61] RFC 4791 CalDAV March 2007

7.8.10. Example: Attempt to Query Unsupported Property

 In this example, the client requests the server to return all VEVENT
 components that include an X-ABC-GUID property with a value matching
 "ABC".  However, the server does not support querying that non-
 standard property, and instead returns an error response.
 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: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="X-ABC-GUID">
           <C:text-match>ABC</C:text-match>
         </C:prop-filter>
       </C:comp-filter>
     </C:comp-filter>
   </C:filter>
 </C:calendar-query>
 >> Response <<
 HTTP/1.1 403 Forbidden
 Date: Sat, 11 Nov 2005 09:32:12 GMT
 Content-Type: application/xml; charset="utf-8"
 Content-Length: xxxx
 <?xml version="1.0" encoding="utf-8" ?>
 <D:error>
   <C:supported-filter>
     <C:prop-filter name="X-ABC-GUID"/>
   </C:supported-filter>
 </D:error>

Daboo, et al. Standards Track [Page 62] RFC 4791 CalDAV March 2007

7.9. CALDAV:calendar-multiget REPORT

 The CALDAV:calendar-multiget REPORT is used to retrieve specific
 calendar object resources from within a collection, if the Request-
 URI is a collection, or to retrieve a specific calendar object
 resource, if the Request-URI is a calendar object resource.  This
 report is similar to the CALDAV:calendar-query REPORT (see
 Section 7.8), except that it takes a list of DAV:href elements,
 instead of a CALDAV:filter element, to determine which calendar
 object resources to return.
 Support for the CALDAV:calendar-multiget REPORT is REQUIRED.
 Marshalling:
    The request body MUST be a CALDAV:calendar-multiget XML element
    (see Section 9.10).  If the Request-URI is a collection resource,
    then the DAV:href elements MUST refer to calendar object resources
    within that collection, and they MAY refer to calendar object
    resources at any depth within the collection.  As a result, the
    "Depth" header MUST be ignored by the server and SHOULD NOT be
    sent by the client.  If the Request-URI refers to a non-collection
    resource, then there MUST be a single DAV:href element that is
    equivalent to the Request-URI.
    The response body for a successful request MUST be a DAV:
    multistatus XML element.
    The response body for a successful CALDAV:calendar-multiget REPORT
    request MUST contain a DAV:response element for each calendar
    object resource referenced by the provided set of DAV:href
    elements.  Calendar data is being returned in the CALDAV:calendar-
    data element inside the DAV:prop element.
    In the case of an error accessing any of the provided DAV:href
    resources, the server MUST return the appropriate error status
    code in the DAV:status element of the corresponding DAV:response
    element.
 Preconditions:
    (CALDAV:supported-calendar-data): The attributes "content-type"
    and "version" of the CALDAV:calendar-data XML elements (see
    Section 9.6) specify a media type supported by the server for
    calendar object resources.
    (CALDAV:min-date-time): Any XML element specifying a range of time
    MUST have its start or end DATE or DATE-TIME values greater than

Daboo, et al. Standards Track [Page 63] RFC 4791 CalDAV March 2007

    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 request;
    (CALDAV:max-date-time): Any XML element specifying a range of time
    MUST have its start or end DATE or DATE-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 request;
 Postconditions:
    None.

7.9.1. Example: Successful CALDAV:calendar-multiget REPORT

 In this example, the client requests the server to return specific
 properties of the VEVENT components referenced by specific URIs.  In
 addition, the DAV:getetag property is also requested and returned as
 part of the response.  Note that in this example, the resource at
 http://cal.example.com/bernard/work/mtg1.ics does not exist,
 resulting in an error status response.
 See Appendix B for the calendar data being targeted by this example.
 >> Request <<
 REPORT /bernard/work/ 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:calendar-multiget xmlns:D="DAV:"
                  xmlns:C="urn:ietf:params:xml:ns:caldav">
   <D:prop>
     <D:getetag/>
     <C:calendar-data/>
   </D:prop>
   <D:href>/bernard/work/abcd1.ics</D:href>
   <D:href>/bernard/work/mtg1.ics</D:href>
 </C:calendar-multiget>
 >> Response <<
 HTTP/1.1 207 Multi-Status
 Date: Sat, 11 Nov 2006 09:32:12 GMT
 Content-Type: application/xml; charset="utf-8"

Daboo, et al. Standards Track [Page 64] RFC 4791 CalDAV March 2007

 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/abcd1.ics</D:href>
     <D:propstat>
       <D:prop>
         <D:getetag>"fffff-abcd1"</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:20060206T001102Z
 DTSTART;TZID=US/Eastern:20060102T100000
 DURATION:PT1H
 SUMMARY:Event #1
 Description:Go Steelers!
 UID:74855313FA803DA593CD579A@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/mtg1.ics</D:href>
     <D:status>HTTP/1.1 404 Not Found</D:status>

Daboo, et al. Standards Track [Page 65] RFC 4791 CalDAV March 2007

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

7.10. CALDAV:free-busy-query REPORT

 The CALDAV:free-busy-query REPORT generates a VFREEBUSY component
 containing free busy information for all the calendar object
 resources targeted by the request and that have the CALDAV:read-free-
 busy or DAV:read privilege granted to the current user.
 Only VEVENT components without a TRANSP property or with the TRANSP
 property set to OPAQUE, and VFREEBUSY components SHOULD be considered
 in generating the free busy time information.
 In the case of VEVENT components, the free or busy time type (FBTYPE)
 of the FREEBUSY properties in the returned VFREEBUSY component SHOULD
 be derived from the value of the TRANSP and STATUS properties, as
 outlined in the table below:
       +---------------------------++------------------+
       |          VEVENT           ||    VFREEBUSY     |
       +-------------+-------------++------------------+
       | TRANSP      | STATUS      || FBTYPE           |
       +=============+=============++==================+
       |             | CONFIRMED   || BUSY             |
       |             | (default)   ||                  |
       | OPAQUE      +-------------++------------------+
       | (default)   | CANCELLED   || FREE             |
       |             +-------------++------------------+
       |             | TENTATIVE   || BUSY-TENTATIVE   |
       |             +-------------++------------------+
       |             | x-name      || BUSY or          |
       |             |             || x-name           |
       +-------------+-------------++------------------+
       |             | CONFIRMED   ||                  |
       | TRANSPARENT | CANCELLED   || FREE             |
       |             | TENTATIVE   ||                  |
       |             | x-name      ||                  |
       +-------------+-------------++------------------+
 Duplicate busy time periods with the same FBTYPE parameter value
 SHOULD NOT be specified in the returned VFREEBUSY component.  Servers
 SHOULD coalesce consecutive or overlapping busy time periods of the
 same type.  Busy time periods with different FBTYPE parameter values
 MAY overlap.
 Support for the CALDAV:free-busy-query REPORT is REQUIRED.

Daboo, et al. Standards Track [Page 66] RFC 4791 CalDAV March 2007

 Marshalling:
    The request body MUST be a CALDAV:free-busy-query XML element (see
    Section 9.11), which MUST contain exactly one CALDAV:time-range
    XML element, as defined in Section 9.9.
    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 an iCalendar
    object that contains exactly one VFREEBUSY component that
    describes the busy time intervals for the calendar object
    resources containing VEVENT, or VFREEBUSY components that satisfy
    the Depth value and for which the current user is at least granted
    the CALDAV:read-free-busy privilege.  If no calendar object
    resources are found to satisfy these conditions, a VFREEBUSY
    component with no FREEBUSY property MUST be returned.  This report
    only returns busy time information.  Free time information can be
    inferred from the returned busy time information.
    If the current user is not granted the CALDAV:read-free-busy or
    DAV:read privileges on the Request-URI, the CALDAV:free-busy-query
    REPORT request MUST fail and return a 404 (Not Found) status
    value.  This restriction will prevent users from discovering URLs
    of resources for which they are only granted the CALDAV:read-free-
    busy privilege.
    The CALDAV:free-busy-query REPORT request can only be run against
    a collection (either a regular collection or a calendar
    collection).  An attempt to run the report on a calendar object
    resource MUST fail and return a 403 (Forbidden) status value.
 Preconditions:
    None.
 Postconditions:
    (DAV:number-of-matches-within-limits): The number of matching
    calendar object resources must fall within server-specific,
    predefined limits.  For example, this postcondition might fail if
    the specified CALDAV:time-range would cause an extremely large
    number of calendar object resources to be considered in computing
    the response.

Daboo, et al. Standards Track [Page 67] RFC 4791 CalDAV March 2007

7.10.1. Example: Successful CALDAV:free-busy-query REPORT

 In this example, the client requests the server to return free busy
 information on the calendar collection /bernard/work/, between 9:00
 A.M. and 5:00 P.M. EST (2:00 P.M. and 10:00 P.M. UTC) on the January
 4, 2006.  The server responds, indicating two busy time intervals of
 one hour, one of which is tentative.
 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:free-busy-query xmlns:C="urn:ietf:params:xml:ns:caldav">
   <C:time-range start="20060104T140000Z"
                   end="20060105T220000Z"/>
 </C:free-busy-query>
 >> Response <<
 HTTP/1.1 200 OK
 Date: Sat, 11 Nov 2006 09:32:12 GMT
 Content-Type: text/calendar
 Content-Length: xxxx
 BEGIN:VCALENDAR
 VERSION:2.0
 PRODID:-//Example Corp.//CalDAV Server//EN
 BEGIN:VFREEBUSY
 DTSTAMP:20050125T090000Z
 DTSTART:20060104T140000Z
 DTEND:20060105T220000Z
 FREEBUSY;FBTYPE=BUSY-TENTATIVE:20060104T150000Z/PT1H
 FREEBUSY:20060104T190000Z/PT1H
 END:VFREEBUSY
 END:VCALENDAR

Daboo, et al. Standards Track [Page 68] RFC 4791 CalDAV March 2007

8. Guidelines

8.1. Client-to-Client Interoperability

 There are a number of actions clients can take that will be legal
 (the server will not return errors), but that can degrade
 interoperability with other client implementations accessing the same
 data.  For example, a recurrence rule could be replaced with a set of
 recurrence dates, a single recurring event could be replaced with a
 set of independent resources to represent each recurrence, or the
 start/end time values can be translated from the original time zone
 to another time zone.  Although this advice amounts to iCalendar
 interoperability best practices and is not limited only to CalDAV
 usage, interoperability problems are likely to be more evident in
 CalDAV use cases.

8.2. Synchronization Operations

 WebDAV already provides functionality required to synchronize a
 collection or set of collections, to make changes offline, and
 provides a simple way to resolve conflicts when reconnected.  ETags
 are the key to making this work, but these are not required of all
 WebDAV servers.  Since offline functionality is more important to
 calendar applications than to some other WebDAV applications, CalDAV
 servers MUST support ETags, as specified in Section 5.3.4.

8.2.1. Use of Reports

8.2.1.1. Restrict the Time Range

 The reports provided in CalDAV can be used by clients to optimize
 their performance in terms of network bandwidth usage and resource
 consumption on the local client machine.  Both are certainly major
 considerations for mobile or handheld devices with limited capacity,
 but they are also relevant to desktop client applications in cases
 where the calendar collections contain large amounts of data.
 Typically, clients present calendar data to users in views that span
 a finite time interval, so whenever possible, clients should only
 retrieve calendar components from the server using CALDAV:calendar-
 query REPORT, combined with a CALDAV:time-range element, to limit the
 set of returned components to just those needed to populate the
 current view.

Daboo, et al. Standards Track [Page 69] RFC 4791 CalDAV March 2007

8.2.1.2. Synchronize by Time Range

 Typically in a calendar, historical data (events, to-dos, etc. that
 have completed prior to the current date) do not change, though they
 may be deleted.  As a result, a client can speed up the
 synchronization process by only considering data for the present time
 and the future up to a reasonable limit (e.g., one week, one month).
 If the user then tries to examine a portion of the calendar outside
 the range that has been synchronized, the client can perform another
 synchronization operation on the new time interval being examined.
 This "just-in-time" synchronization can minimize bandwidth for common
 user interaction behaviors.

8.2.1.3. Synchronization Process

 If a client wants to support calendar data synchronization, as
 opposed to downloading calendar data each time it is needed, the
 client needs to cache the calendar object resource's URI and ETag,
 along with the actual calendar data.  While the URI remains static
 for the lifetime of the calendar object resource, the ETag will
 change with each successive change to the calendar object resource.
 Thus, to synchronize a local data cache with the server, the client
 can first fetch the URI/ETag pairs for the time interval being
 considered, and compare those results with the cached data.  Any
 cached component whose ETag differs from that on the server needs to
 be refreshed.
 In order to properly detect the changes between the server and client
 data, the client will need to keep a record of which calendar object
 resources have been created, changed, or deleted since the last
 synchronization operation so that it can reconcile those changes with
 the data on the server.
 Here's an example of how to do that:
 The client issues a CALDAV:calendar-query REPORT request for a
 specific time range and asks for only the DAV:getetag property to be
 returned:

Daboo, et al. Standards Track [Page 70] RFC 4791 CalDAV March 2007

 REPORT /bernard/work/ HTTP/1.1
 Host: cal.example.com
 Depth: 1
 Content-Type: application/xml; charset="utf-8"
 Content-Length: xxxx
 <?xml version="1.0" encoding="utf-8" ?>
 <C:calendar-query xmlns:D="DAV:"
                   xmlns:C="urn:ietf:params:xml:ns:caldav">
   <D:prop>
     <D:getetag/>
   </D:prop>
   <C:filter>
     <C:comp-filter name="VCALENDAR">
       <C:comp-filter name="VEVENT">
         <C:time-range start="20040902T000000Z"
                         end="20040903T000000Z"/>
       </C:comp-filter>
     </C:comp-filter>
   </C:filter>
 </C:calendar-query>
 The client then uses the results to determine which calendar object
 resources have changed, been created, or deleted on the server, and
 how those relate to locally cached calendar object resources that may
 have changed, been created, or deleted.  If the client determines
 that there are calendar object resources on the server that need to
 be fetched, the client issues a CALDAV:calendar-multiget REPORT
 request to fetch its calendar data:
 REPORT /bernard/work/ 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:calendar-multiget xmlns:D="DAV:"
                      xmlns:C="urn:ietf:params:xml:ns:caldav">
   <D:prop>
     <D:getetag/>
     <C:calendar-data/>
   </D:prop>
   <D:href>/bernard/work/abcd1.ics</D:href>
   <D:href>/bernard/work/mtg1.ics</D:href>
 </C:calendar-multiget>

Daboo, et al. Standards Track [Page 71] RFC 4791 CalDAV March 2007

8.2.2. Restrict the Properties Returned

 A client may not need all the calendar properties of a calendar
 object resource when presenting information to the user.  Since some
 calendar property values can be large (e.g., ATTACH or ATTENDEE), a
 client can choose to restrict the calendar properties to be returned
 in a calendaring REPORT request to those it knows it will use.
 However, if a client needs to make a change to a calendar object
 resource, it can only change the entire calendar object resource via
 a PUT request.  There is currently no way to incrementally make a
 change to a set of calendar properties of a calendar object resource.
 As a result, the client will have to get the entire calendar object
 resource that is being changed.

8.3. Use of Locking

 WebDAV locks can be used to prevent two clients that are modifying
 the same resource from either overwriting each others' changes
 (though that problem can also be solved by using ETags) or wasting
 time making changes that will conflict with another set of changes.
 In a multi-user calendar system, an interactive calendar client could
 lock an event while the user is editing the event, and unlock the
 event when the user finishes or cancels.  Locks can also be used to
 prevent changes while data is being reorganized.  For example, a
 calendar client might lock two calendar collections prior to moving a
 bunch of calendar resources from one to another.
 Clients are responsible for requesting a lock timeout period that is
 appropriate to the use case.  When the user explicitly decides to
 reserve a resource and prevent other changes, a long timeout might be
 appropriate, but in cases where the client automatically decides to
 lock the resource, the timeout should be short (and the client can
 always refresh the lock should it need to).  A short lock timeout
 means that if the client is unable to remove the lock, the other
 calendar users aren't prevented from making changes.

8.4. Finding Calendars

 Much of the time, a calendar client (or agent) will discover a new
 calendar's location by being provided directly with the URL.  For
 example, a user will type his or her own calendar location into
 client configuration information or copy and paste a URL from email
 into the calendar application.  The client need only confirm that the
 URL points to a resource that is a calendar collection.  The client
 may also be able to browse WebDAV collections to find calendar
 collections.

Daboo, et al. Standards Track [Page 72] RFC 4791 CalDAV March 2007

 The choice of HTTP URLs means that calendar object resources are
 backward compatible with existing software, but does have the
 disadvantage that existing software does not usually know to look at
 the OPTIONS response to that URL to determine what can be done with
 it.  This is somewhat of a barrier for WebDAV usage as well as with
 CalDAV usage.  This specification does not offer a way through this
 other than making the information available in the OPTIONS response
 should this be requested.
 For calendar sharing and scheduling use cases, one might wish to find
 the calendar belonging to another user.  If the other user has a
 calendar in the same repository, that calendar can be found by using
 the principal namespace required by WebDAV ACL support.  For other
 cases, the authors have no universal solution, but implementers can
 consider whether to use vCard [RFC2426] or LDAP [RFC4511] standards
 together with calendar attributes [RFC2739].
 Because CalDAV requires servers to support WebDAV ACL [RFC3744],
 including principal namespaces, and with the addition of the CALDAV:
 calendar-home-set property, there are a couple options for CalDAV
 clients to find one's own calendar or another user's calendar.
 In this case, a DAV:principal-match REPORT is used to find a named
 property (the CALDAV:calendar-home-set) on the Principal-URL of the
 current user.  Using this, a WebDAV client can learn "who am I" and
 "where are my calendars".  The REPORT request body looks like this:
 <?xml version="1.0" encoding="utf-8" ?>
 <D:principal-match xmlns:D="DAV:">
   <D:self/>
   <D:prop>
     <C:calendar-home-set
        xmlns:C="urn:ietf:params:xml:ns:caldav"/>
   </D:prop>
 </D:principal-match>
 To find other users' calendars, the DAV:principal-property-search
 REPORT can be used to filter on some properties and return others.
 To search for a calendar owned by a user named "Laurie", the REPORT
 request body would look like this:

Daboo, et al. Standards Track [Page 73] RFC 4791 CalDAV March 2007

 <?xml version="1.0" encoding="utf-8" ?>
 <D:principal-property-search xmlns:D="DAV:">
   <D:property-search>
     <D:prop>
       <D:displayname/>
     </D:prop>
     <D:match>Laurie</D:match>
   </D:property-search>
   <D:prop>
     <C:calendar-home-set
        xmlns:C="urn:ietf:params:xml:ns:caldav"/>
     <D:displayname/>
   </D:prop>
 </D:principal-property-search>
 The server performs a case-sensitive or caseless search for a
 matching string subset of "Laurie" within the DAV:displayname
 property.  Thus, the server might return "Laurie Dusseault", "Laurier
 Desruisseaux", or "Wilfrid Laurier" as matching DAV:displayname
 values, and return the calendars for each of these.

8.5. Storing and Using Attachments

 CalDAV clients MAY create attachments in calendar components either
 as inline or external.  This section contains some guidelines for
 creating and managing attachments.

8.5.1. Inline Attachments

 CalDAV clients MUST support inline attachments as specified in
 iCalendar [RFC2445].  CalDAV servers MUST support inline attachments,
 so clients can rely on being able to create attachments this way.  On
 the other hand, inline attachments have some drawbacks:
 o  Servers MAY impose limitations on the size of calendar object
    resources (i.e., refusing PUT requests of very large iCalendar
    objects).  Servers that impose such limitations MUST use the
    CALDAV:max-resource-size property on a calendar collection to
    inform the client as to what the limitation is (see
    Section 5.2.5).
 o  Servers MAY impose storage quota limitations on calendar
    collections (See [RFC4331]).
 o  Any change to a calendar object resource containing an inline
    attachment requires the entire inline attachment to be re-
    uploaded.

Daboo, et al. Standards Track [Page 74] RFC 4791 CalDAV March 2007

 o  Clients synchronizing a changed calendar object resource have to
    download the entire calendar object resource, even if the
    attachment is unchanged.

8.5.2. External Attachments

 CalDAV clients SHOULD support downloading of external attachments
 referenced by arbitrary URI schemes, by either processing them
 directly, or by passing the attachment URI to a suitable "helper
 application" for processing, if such an application exists.  CalDAV
 clients MUST support downloading of external attachments referenced
 by the "http" or "https" URI schemes.  An external attachment could
 be:
 o  In a collection in the calendar collection containing the calendar
    object resource;
 o  Somewhere else in the same repository that hosts the calendar
    collection; or
 o  On an HTTP or FTP server elsewhere.
 CalDAV servers MAY provide support for child collections in calendar
 collections.  CalDAV servers MAY allow the MKCOL method to create
 child collections in calendar collections.  Child collections of
 calendar collections MAY contain any type of resource except calendar
 collections that they MUST NOT contain.  Some CalDAV servers won't
 allow child collections in calendar collections, and it may be
 possible on such a server to discover other locations where
 attachments can be stored.
 Clients are entirely responsible for maintaining reference
 consistency with calendar components that link to external
 attachments.  A client deleting a calendar component with an external
 attachment might therefore also delete the attachment if that's
 appropriate; however, appropriateness can be very hard to determine.
 A new component might easily reference some pre-existing Web resource
 that is intended to have independent existence from the calendar
 component (the "attachment" could be a major proposal to be discussed
 in a meeting, for instance).  Best practices will probably emerge and
 should probably be documented, but for now, clients should be wary of
 engaging in aggressive "cleanup" of external attachments.  A client
 could involve the user in making decisions about removing
 unreferenced documents, or a client could be conservative in only
 deleting attachments it had created.
 Also, clients are responsible for consistency of permissions when
 using external attachments.  One reason for servers to support the

Daboo, et al. Standards Track [Page 75] RFC 4791 CalDAV March 2007

 storage of attachments within child collections of calendar
 collections is that ACL inheritance might make it easier to grant the
 same permissions to attachments that are granted on the calendar
 collection.  Otherwise, it can be very difficult to keep permissions
 synchronized.  With attachments stored on separate repositories, it
 can be impossible to keep permissions consistent -- the two
 repositories may not support the same permissions or have the same
 set of principals.  Some systems have used tickets or other anonymous
 access control mechanisms to provide partially satisfactory solutions
 to these kinds of problems.

8.6. Storing and Using Alarms

 Note that all CalDAV calendar collections (including those the user
 might treat as public or group calendars) can contain alarm
 information on events and to-dos.  Users can synchronize a calendar
 between multiple devices and decide to have alarms execute on a
 different device than the device that created the alarm.  Not all
 alarm action types are completely interoperable (e.g., those that
 name a sound file to play).
    When the action is AUDIO and the client is configured to execute
    the alarm, the client SHOULD play the suggested sound if it's
    available or play another sound, but SHOULD NOT rewrite the alarm
    just to replace the suggested sound with a sound that's locally
    available.
    When the action is DISPLAY and the client is configured to execute
    the alarm, the client SHOULD execute a display alarm by displaying
    according to the suggested description or some reasonable
    replacement, but SHOULD NOT rewrite the alarm for its own
    convenience.
    When the action is EMAIL and the client is incapable of sending
    email, it SHOULD ignore the alarm, but it MUST continue to
    synchronize the alarm itself.
    This specification makes no recommendations about executing alarms
    of type PROCEDURE, except to note that clients are advised to take
    care to avoid creating security holes by executing these.
 Non-interoperable alarm information (e.g., should somebody define a
 color to be used in a display alarm) should be put in non-standard
 properties inside the VALARM component in order to keep the basic
 alarm usable on all devices.
 Clients that allow changes to calendar object resources MUST
 synchronize the alarm data that already exists in the resources.

Daboo, et al. Standards Track [Page 76] RFC 4791 CalDAV March 2007

 Clients MAY execute alarms that are downloaded in this fashion,
 possibly based on user preference.  If a client is only doing read
 operations on a calendar and there is no risk of losing alarm
 information, then the client MAY discard alarm information.
 This specification makes no attempt to provide multi-user alarms on
 group calendars or to find out for whom an alarm is intended.
 Addressing those issues might require extensions to iCalendar; for
 example, to store alarms per-user, or to indicate for which user a
 VALARM was intended.  In the meantime, clients might maximize
 interoperability by generally not uploading alarm information to
 public, group, or resource calendars.

9. XML Element Definitions

9.1. CALDAV:calendar XML Element

 Name:  calendar
 Namespace:  urn:ietf:params:xml:ns:caldav
 Purpose:  Specifies the resource type of a calendar collection.
 Description:  See Section 4.2.
 Definition:
       <!ELEMENT calendar EMPTY>

9.2. CALDAV:mkcalendar XML Element

 Name:  mkcalendar
 Namespace:  urn:ietf:params:xml:ns:caldav
 Purpose:  Specifies a request that includes the WebDAV property
    values to be set for a calendar collection resource when it is
    created.
 Description:  See Section 5.3.1.
 Definition:
       <!ELEMENT mkcalendar (DAV:set)>

Daboo, et al. Standards Track [Page 77] RFC 4791 CalDAV March 2007

9.3. CALDAV:mkcalendar-response XML Element

 Name:  mkcalendar-response
 Namespace:  urn:ietf:params:xml:ns:caldav
 Purpose:  Specifies a response body for a successful MKCALENDAR
    request.
 Description:  See Section 5.3.1.
 Definition:
       <!ELEMENT mkcalendar-response ANY>

9.4. CALDAV:supported-collation XML Element

 Name:  supported-collation
 Namespace:  urn:ietf:params:xml:ns:caldav
 Purpose:  Identifies a single collation via its collation identifier,
    as defined by [RFC4790].
 Description:  The CALDAV:supported-collation contains the text of a
    collation identifier, as described in Section 7.5.1.
 Definition:
       <!ELEMENT supported-collation (#PCDATA)>
       PCDATA value: collation identifier

9.5. CALDAV:calendar-query XML Element

 Name:  calendar-query
 Namespace:  urn:ietf:params:xml:ns:caldav
 Purpose:  Defines a report for querying calendar object resources.
 Description:  See Section 7.8.
 Definition:
       <!ELEMENT calendar-query ((DAV:allprop |
                                  DAV:propname |
                                  DAV:prop)?, filter, timezone?)>

Daboo, et al. Standards Track [Page 78] RFC 4791 CalDAV March 2007

9.6. CALDAV:calendar-data XML Element

 Name:  calendar-data
 Namespace:  urn:ietf:params:xml:ns:caldav
 Purpose:  Specified one of the following:
    1.  A supported media type for calendar object resources when
        nested in the CALDAV:supported-calendar-data property;
    2.  The parts of a calendar object resource should be returned by
        a calendaring report;
    3.  The content of a calendar object resource in a response to a
        calendaring report.
 Description:  When nested in the CALDAV:supported-calendar-data
    property, the CALDAV:calendar-data XML element specifies a media
    type supported by the CalDAV server for calendar object resources.
    When used in a calendaring REPORT request, the CALDAV:calendar-
    data XML element specifies which parts of calendar object
    resources need to be returned in the response.  If the CALDAV:
    calendar-data XML element doesn't contain any CALDAV:comp element,
    calendar object resources will be returned in their entirety.
    Finally, when used in a calendaring REPORT response, the CALDAV:
    calendar-data XML element specifies the content of a calendar
    object resource.  Given that XML parsers normalize the two-
    character sequence CRLF (US-ASCII decimal 13 and US-ASCII decimal
    10) to a single LF character (US-ASCII decimal 10), the CR
    character (US-ASCII decimal 13) MAY be omitted in calendar object
    resources specified in the CALDAV:calendar-data XML element.
    Furthermore, calendar object resources specified in the CALDAV:
    calendar-data XML element MAY be invalid per their media type
    specification if the CALDAV:calendar-data XML element part of the
    calendaring REPORT request did not specify required properties
    (e.g., UID, DTSTAMP, etc.), or specified a CALDAV:prop XML element
    with the "novalue" attribute set to "yes".
 Note:  The CALDAV:calendar-data XML element is specified in requests
    and responses inside the DAV:prop XML element as if it were a
    WebDAV property.  However, the CALDAV:calendar-data XML element is
    not a WebDAV property and, as such, is not returned in PROPFIND
    responses, nor used in PROPPATCH requests.

Daboo, et al. Standards Track [Page 79] RFC 4791 CalDAV March 2007

 Note:  The iCalendar data embedded within the CALDAV:calendar-data
    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-data EMPTY>
       when nested in the CALDAV:supported-calendar-data property
       to specify a supported media type for calendar object
       resources;
       <!ELEMENT calendar-data (comp?,
                                (expand | limit-recurrence-set)?,
                                limit-freebusy-set?)>
       when nested in the DAV:prop XML element in a calendaring
       REPORT request to specify which parts of calendar object
       resources should be returned in the response;
       <!ELEMENT calendar-data (#PCDATA)>
       PCDATA value: iCalendar object
       when nested in the DAV:prop XML element in a calendaring
       REPORT response to specify the content of a returned
       calendar object resource.
       <!ATTLIST calendar-data content-type CDATA "text/calendar"
                               version CDATA "2.0">
       content-type value: a MIME media type
       version value: a version string
       attributes can be used on all three variants of the
       CALDAV:calendar-data XML element.

9.6.1. CALDAV:comp XML Element

 Name:  comp
 Namespace:  urn:ietf:params:xml:ns:caldav
 Purpose:  Defines which component types to return.

Daboo, et al. Standards Track [Page 80] RFC 4791 CalDAV March 2007

 Description:  The name value is a calendar component name (e.g.,
    VEVENT).
 Definition:
       <!ELEMENT comp ((allprop | prop*), (allcomp | comp*))>
       <!ATTLIST comp name CDATA #REQUIRED>
       name value: a calendar component name
 Note:  The CALDAV:prop and CALDAV:allprop elements have the same name
    as the DAV:prop and DAV:allprop elements defined in [RFC2518].
    However, the CALDAV:prop and CALDAV:allprop elements are defined
    in the "urn:ietf:params:xml:ns:caldav" namespace instead of the
    "DAV:" namespace.

9.6.2. CALDAV:allcomp XML Element

 Name:  allcomp
 Namespace:  urn:ietf:params:xml:ns:caldav
 Purpose:  Specifies that all components shall be returned.
 Description:  The CALDAV:allcomp XML element can be used when the
    client wants all types of components returned by a calendaring
    REPORT request.
 Definition:
       <!ELEMENT allcomp EMPTY>

9.6.3. CALDAV:allprop XML Element

 Name:  allprop
 Namespace:  urn:ietf:params:xml:ns:caldav
 Purpose:  Specifies that all properties shall be returned.
 Description:  The CALDAV:allprop XML element can be used when the
    client wants all properties of components returned by a
    calendaring REPORT request.
 Definition:
       <!ELEMENT allprop EMPTY>

Daboo, et al. Standards Track [Page 81] RFC 4791 CalDAV March 2007

 Note:  The CALDAV:allprop element has the same name as the DAV:
    allprop element defined in [RFC2518].  However, the CALDAV:allprop
    element is defined in the "urn:ietf:params:xml:ns:caldav"
    namespace instead of the "DAV:" namespace.

9.6.4. CALDAV:prop XML Element

 Name:  prop
 Namespace:  urn:ietf:params:xml:ns:caldav
 Purpose:  Defines which properties to return in the response.
 Description:  The "name" attribute specifies the name of the calendar
    property to return (e.g., ATTENDEE).  The "novalue" attribute can
    be used by clients to request that the actual value of the
    property not be returned (if the "novalue" attribute is set to
    "yes").  In that case, the server will return just the iCalendar
    property name and any iCalendar parameters and a trailing ":"
    without the subsequent value data.
 Definition:
       <!ELEMENT prop EMPTY>
       <!ATTLIST prop name CDATA #REQUIRED
                      novalue (yes | no) "no">
       name value: a calendar property name
       novalue value: "yes" or "no"
 Note:  The CALDAV:prop element has the same name as the DAV:prop
    element defined in [RFC2518].  However, the CALDAV:prop element is
    defined in the "urn:ietf:params:xml:ns:caldav" namespace instead
    of the "DAV:" namespace.

9.6.5. CALDAV:expand XML Element

 Name:  expand
 Namespace:  urn:ietf:params:xml:ns:caldav
 Purpose:  Forces the server to expand recurring components into
    individual recurrence instances.
 Description:  The CALDAV:expand XML element specifies that for a
    given calendaring REPORT request, the server MUST expand the
    recurrence set into calendar components that define exactly one

Daboo, et al. Standards Track [Page 82] RFC 4791 CalDAV March 2007

    recurrence instance, and MUST return only those whose scheduled
    time intersect a specified time range.
    The "start" attribute specifies the inclusive start of the time
    range, and the "end" attribute specifies the non-inclusive end of
    the time range.  Both attributes are specified as date with UTC
    time value.  The value of the "end" attribute MUST be greater than
    the value of the "start" attribute.
    The server MUST use the same logic as defined for CALDAV:time-
    range to determine if a recurrence instance intersects the
    specified time range.
    Recurring components, other than the initial instance, MUST
    include a RECURRENCE-ID property indicating which instance they
    refer to.
    The returned calendar components MUST NOT use recurrence
    properties (i.e., EXDATE, EXRULE, RDATE, and RRULE) and MUST NOT
    have reference to or include VTIMEZONE components.  Date and local
    time with reference to time zone information MUST be converted
    into date with UTC time.
 Definition:
       <!ELEMENT expand EMPTY>
       <!ATTLIST expand start CDATA #REQUIRED
                        end   CDATA #REQUIRED>
       start value: an iCalendar "date with UTC time"
       end value: an iCalendar "date with UTC time"

9.6.6. CALDAV:limit-recurrence-set XML Element

 Name:  limit-recurrence-set
 Namespace:  urn:ietf:params:xml:ns:caldav
 Purpose:  Specifies a time range to limit the set of "overridden
    components" returned by the server.
 Description:  The CALDAV:limit-recurrence-set XML element specifies
    that for a given calendaring REPORT request, the server MUST
    return, in addition to the "master component", only the
    "overridden components" that impact a specified time range.  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

Daboo, et al. Standards Track [Page 83] RFC 4791 CalDAV March 2007

    times -- the ones that would have been used if the instance were
    not overridden -- overlap the time range.
    The "start" attribute specifies the inclusive start of the time
    range, and the "end" attribute specifies the non-inclusive end of
    the time range.  Both attributes are specified as date with UTC
    time value.  The value of the "end" attribute MUST be greater than
    the value of the "start" attribute.
    The server MUST use the same logic as defined for CALDAV:time-
    range to determine if the current or original scheduled time of an
    "overridden" recurrence instance intersects the specified time
    range.
    Overridden components that have a RANGE parameter on their
    RECURRENCE-ID property may specify one or more instances in the
    recurrence set, and some of those instances may fall within the
    specified time range or may have originally fallen within the
    specified time range prior to being overridden.  If that is the
    case, the overridden component MUST be included in the results, as
    it has a direct impact on the interpretation of instances within
    the specified time range.
 Definition:
       <!ELEMENT limit-recurrence-set EMPTY>
       <!ATTLIST limit-recurrence-set start CDATA #REQUIRED
                                      end   CDATA #REQUIRED>
       start value: an iCalendar "date with UTC time"
       end value: an iCalendar "date with UTC time"

9.6.7. CALDAV:limit-freebusy-set XML Element

 Name:  limit-freebusy-set
 Namespace:  urn:ietf:params:xml:ns:caldav
 Purpose:  Specifies a time range to limit the set of FREEBUSY values
    returned by the server.
 Description:  The CALDAV:limit-freebusy-set XML element specifies
    that for a given calendaring REPORT request, the server MUST only
    return the FREEBUSY property values of a VFREEBUSY component that
    intersects a specified time range.
    The "start" attribute specifies the inclusive start of the time
    range, and the "end" attribute specifies the non-inclusive end of

Daboo, et al. Standards Track [Page 84] RFC 4791 CalDAV March 2007

    the time range.  Both attributes are specified as "date with UTC
    time" value.  The value of the "end" attribute MUST be greater
    than the value of the "start" attribute.
    The server MUST use the same logic as defined for CALDAV:time-
    range to determine if a FREEBUSY property value intersects the
    specified time range.
 Definition:
       <!ELEMENT limit-freebusy-set EMPTY>
       <!ATTLIST limit-freebusy-set start CDATA #REQUIRED
                                    end   CDATA #REQUIRED>
       start value: an iCalendar "date with UTC time"
       end value: an iCalendar "date with UTC time"

9.7. CALDAV:filter XML Element

 Name:  filter
 Namespace:  urn:ietf:params:xml:ns:caldav
 Purpose:  Specifies a filter to limit the set of calendar components
    returned by the server.
 Description:  The CALDAV:filter XML element specifies the search
    filter used to limit the calendar components returned by a
    calendaring REPORT request.
 Definition:
       <!ELEMENT filter (comp-filter)>

9.7.1. CALDAV:comp-filter XML Element

 Name:  comp-filter
 Namespace:  urn:ietf:params:xml:ns:caldav
 Purpose:  Specifies search criteria on calendar components.
 Description:  The CALDAV:comp-filter XML element specifies a query
    targeted at the calendar object (i.e., VCALENDAR) or at a specific
    calendar component type (e.g., VEVENT).  The scope of the
    CALDAV:comp-filter XML element is the calendar object when used as
    a child of the CALDAV:filter XML element.  The scope of the
    CALDAV:comp-filter XML element is the enclosing calendar component

Daboo, et al. Standards Track [Page 85] RFC 4791 CalDAV March 2007

    when used as a child of another CALDAV:comp-filter XML element.  A
    CALDAV:comp-filter is said to match if:
  • The CALDAV:comp-filter XML element is empty and the calendar

object or calendar component type specified by the "name"

       attribute exists in the current scope;
    or:
  • The CALDAV:comp-filter XML element contains a CALDAV:is-not-

defined XML element and the calendar object or calendar

       component type specified by the "name" attribute does not exist
       in the current scope;
    or:
  • The CALDAV:comp-filter XML element contains a CALDAV:time-range

XML element and at least one recurrence instance in the

       targeted calendar component is scheduled to overlap the
       specified time range, and all specified CALDAV:prop-filter and
       CALDAV:comp-filter child XML elements also match the targeted
       calendar component;
    or:
  • The CALDAV:comp-filter XML element only contains CALDAV:prop-

filter and CALDAV:comp-filter child XML elements that all match

       the targeted calendar component.
 Definition:
       <!ELEMENT comp-filter (is-not-defined | (time-range?,
                              prop-filter*, comp-filter*))>
       <!ATTLIST comp-filter name CDATA #REQUIRED>
       name value: a calendar object or calendar component
                   type (e.g., VEVENT)

9.7.2. CALDAV:prop-filter XML Element

 Name:  prop-filter
 Namespace:  urn:ietf:params:xml:ns:caldav
 Purpose:  Specifies search criteria on calendar properties.
 Description:  The CALDAV:prop-filter XML element specifies a query
    targeted at a specific calendar property (e.g., CATEGORIES) in the

Daboo, et al. Standards Track [Page 86] RFC 4791 CalDAV March 2007

    scope of the enclosing calendar component.  A calendar property is
    said to match a CALDAV:prop-filter if:
  • The CALDAV:prop-filter XML element is empty and a property of

the type specified by the "name" attribute exists in the

       enclosing calendar component;
    or:
  • The CALDAV:prop-filter XML element contains a CALDAV:is-not-

defined XML element and no property of the type specified by

       the "name" attribute exists in the enclosing calendar
       component;
    or:
  • The CALDAV:prop-filter XML element contains a CALDAV:time-range

XML element and the property value overlaps the specified time

       range, and all specified CALDAV:param-filter child XML elements
       also match the targeted property;
    or:
  • The CALDAV:prop-filter XML element contains a CALDAV:text-match

XML element and the property value matches it, and all

       specified CALDAV:param-filter child XML elements also match the
       targeted property;
 Definition:
       <!ELEMENT prop-filter (is-not-defined |
                              ((time-range | text-match)?,
                               param-filter*))>
       <!ATTLIST prop-filter name CDATA #REQUIRED>
       name value: a calendar property name (e.g., ATTENDEE)

9.7.3. CALDAV:param-filter XML Element

 Name:  param-filter
 Namespace:  urn:ietf:params:xml:ns:caldav
 Purpose:  Limits the search to specific parameter values.
 Description:  The CALDAV:param-filter XML element specifies a query
    targeted at a specific calendar property parameter (e.g.,
    PARTSTAT) in the scope of the calendar property on which it is

Daboo, et al. Standards Track [Page 87] RFC 4791 CalDAV March 2007

    defined.  A calendar property parameter is said to match a CALDAV:
    param-filter if:
  • The CALDAV:param-filter XML element is empty and a parameter of

the type specified by the "name" attribute exists on the

       calendar property being examined;
    or:
  • The CALDAV:param-filter XML element contains a CALDAV:is-not-

defined XML element and no parameter of the type specified by

       the "name" attribute exists on the calendar property being
       examined;
 Definition:
       <!ELEMENT param-filter (is-not-defined | text-match?)>
       <!ATTLIST param-filter name CDATA #REQUIRED>
       name value: a property parameter name (e.g., PARTSTAT)

9.7.4. CALDAV:is-not-defined XML Element

 Name:  is-not-defined
 Namespace:  urn:ietf:params:xml:ns:caldav
 Purpose:  Specifies that a match should occur if the enclosing
    component, property, or parameter does not exist.
 Description:  The CALDAV:is-not-defined XML element specifies that a
    match occurs if the enclosing component, property, or parameter
    value specified in a calendaring REPORT request does not exist in
    the calendar data being tested.
 Definition:
       <!ELEMENT is-not-defined EMPTY>

9.7.5. CALDAV:text-match XML Element

 Name:  text-match
 Namespace:  urn:ietf:params:xml:ns:caldav
 Purpose:  Specifies a substring match on a property or parameter
    value.

Daboo, et al. Standards Track [Page 88] RFC 4791 CalDAV March 2007

 Description:  The CALDAV:text-match XML element specifies text used
    for a substring match against the property or parameter value
    specified in a calendaring REPORT request.
    The "collation" attribute is used to select the collation that the
    server MUST use for character string matching.  In the absence of
    this attribute, the server MUST use the "i;ascii-casemap"
    collation.
    The "negate-condition" attribute is used to indicate that this
    test returns a match if the text matches when the attribute value
    is set to "no", or return a match if the text does not match, if
    the attribute value is set to "yes".  For example, this can be
    used to match components with a STATUS property not set to
    CANCELLED.
 Definition:
       <!ELEMENT text-match (#PCDATA)>
       PCDATA value: string
       <!ATTLIST text-match collation        CDATA "i;ascii-casemap"
                            negate-condition (yes | no) "no">

9.8. CALDAV:timezone XML Element

 Name:  timezone
 Namespace:  urn:ietf:params:xml:ns:caldav
 Purpose:  Specifies the time zone component to use when determining
    the results of a report.
 Description:  The CALDAV:timezone XML element specifies that for a
    given calendaring REPORT request, the server MUST rely on the
    specified VTIMEZONE component instead of the CALDAV:calendar-
    timezone property of the calendar collection, in which the
    calendar object resource is contained 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 intersects a CALDAV:time-range
    specified in a CALDAV:calendar-query REPORT.
 Note:  The iCalendar data embedded within the CALDAV: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

Daboo, et al. Standards Track [Page 89] RFC 4791 CalDAV March 2007

    iCalendar data cannot contain the character sequence "]]>", which
    is the end delimiter for the CDATA section.
 Definition:
       <!ELEMENT timezone (#PCDATA)>
       PCDATA value: an iCalendar object with exactly one VTIMEZONE

9.9. CALDAV:time-range XML Element

 Name:  time-range
 Namespace:  urn:ietf:params:xml:ns:caldav
 Purpose:  Specifies a time range to limit the set of calendar
    components returned by the server.
 Description:  The CALDAV:time-range XML element specifies that for a
    given calendaring REPORT request, the server MUST only return the
    calendar object resources that, depending on the context, have a
    component or property whose value intersects a specified time
    range.
    The "start" attribute specifies the inclusive start of the time
    range, and the "end" attribute specifies the non-inclusive end of
    the time range.  Both attributes MUST be specified as "date with
    UTC time" value.  Time ranges open at one end can be specified by
    including only one attribute; however, at least one attribute MUST
    always be present in the CALDAV:time-range element.  If either the
    "start" or "end" attribute is not specified in the CALDAV:time-
    range XML element, assume "-infinity" and "+infinity" as their
    value, respectively.  If both "start" and "end" are present, the
    value of the "end" attribute MUST be greater than the value of the
    "start" attribute.
    Time range tests MUST consider every recurrence instance when
    testing the time range condition; if any one instance matches,
    then the test returns true.  Testing recurrence instances requires
    the server to infer an effective value for DTSTART, DTEND,
    DURATION, and DUE properties for an instance based on the
    recurrence patterns and any overrides.
    A VEVENT component overlaps a given time range if the condition
    for the corresponding component state specified in the table below
    is satisfied.  Note that, as specified in [RFC2445], the DTSTART
    property is REQUIRED in the VEVENT component.  The conditions
    depend on the presence of the DTEND and DURATION properties in the
    VEVENT component.  Furthermore, the value of the DTEND property

Daboo, et al. Standards Track [Page 90] RFC 4791 CalDAV March 2007

    MUST be later in time than the value of the DTSTART property.  The
    duration of a VEVENT component with no DTEND and DURATION
    properties is 1 day (+P1D) when the DTSTART is a DATE value, and 0
    seconds when the DTSTART is a DATE-TIME value.
    +---------------------------------------------------------------+
    | VEVENT has the DTEND property?                                |
    |   +-----------------------------------------------------------+
    |   | VEVENT has the DURATION property?                         |
    |   |   +-------------------------------------------------------+
    |   |   | DURATION property value is greater than 0 seconds?    |
    |   |   |   +---------------------------------------------------+
    |   |   |   | DTSTART property is a DATE-TIME value?            |
    |   |   |   |   +-----------------------------------------------+
    |   |   |   |   | Condition to evaluate                         |
    +---+---+---+---+-----------------------------------------------+
    | Y | N | N | * | (start <  DTEND AND end > DTSTART)            |
    +---+---+---+---+-----------------------------------------------+
    | N | Y | Y | * | (start <  DTSTART+DURATION AND end > DTSTART) |
    |   |   +---+---+-----------------------------------------------+
    |   |   | N | * | (start <= DTSTART AND end > DTSTART)          |
    +---+---+---+---+-----------------------------------------------+
    | N | N | N | Y | (start <= DTSTART AND end > DTSTART)          |
    +---+---+---+---+-----------------------------------------------+
    | N | N | N | N | (start <  DTSTART+P1D AND end > DTSTART)      |
    +---+---+---+---+-----------------------------------------------+
    A VTODO component is said to overlap a given time range if the
    condition for the corresponding component state specified in the
    table below is satisfied.  The conditions depend on the presence
    of the DTSTART, DURATION, DUE, COMPLETED, and CREATED properties
    in the VTODO component.  Note that, as specified in [RFC2445], the
    DUE value MUST be a DATE-TIME value equal to or after the DTSTART
    value if specified.

Daboo, et al. Standards Track [Page 91] RFC 4791 CalDAV March 2007

 +-------------------------------------------------------------------+
 | VTODO has the DTSTART property?                                   |
 |   +---------------------------------------------------------------+
 |   |   VTODO has the DURATION property?                            |
 |   |   +-----------------------------------------------------------+
 |   |   | VTODO has the DUE property?                               |
 |   |   |   +-------------------------------------------------------+
 |   |   |   | VTODO has the COMPLETED property?                     |
 |   |   |   |   +---------------------------------------------------+
 |   |   |   |   | VTODO has the CREATED property?                   |
 |   |   |   |   |   +-----------------------------------------------+
 |   |   |   |   |   | Condition to evaluate                         |
 +---+---+---+---+---+-----------------------------------------------+
 | Y | Y | N | * | * | (start  <= DTSTART+DURATION)  AND             |
 |   |   |   |   |   | ((end   >  DTSTART)  OR                       |
 |   |   |   |   |   |  (end   >= DTSTART+DURATION))                 |
 +---+---+---+---+---+-----------------------------------------------+
 | Y | N | Y | * | * | ((start <  DUE)      OR  (start <= DTSTART))  |
 |   |   |   |   |   | AND                                           |
 |   |   |   |   |   | ((end   >  DTSTART)  OR  (end   >= DUE))      |
 +---+---+---+---+---+-----------------------------------------------+
 | Y | N | N | * | * | (start  <= DTSTART)  AND (end >  DTSTART)     |
 +---+---+---+---+---+-----------------------------------------------+
 | N | N | Y | * | * | (start  <  DUE)      AND (end >= DUE)         |
 +---+---+---+---+---+-----------------------------------------------+
 | N | N | N | Y | Y | ((start <= CREATED)  OR  (start <= COMPLETED))|
 |   |   |   |   |   | AND                                           |
 |   |   |   |   |   | ((end   >= CREATED)  OR  (end   >= COMPLETED))|
 +---+---+---+---+---+-----------------------------------------------+
 | N | N | N | Y | N | (start  <= COMPLETED) AND (end  >= COMPLETED) |
 +---+---+---+---+---+-----------------------------------------------+
 | N | N | N | N | Y | (end    >  CREATED)                           |
 +---+---+---+---+---+-----------------------------------------------+
 | N | N | N | N | N | TRUE                                          |
 +---+---+---+---+---+-----------------------------------------------+
    A VJOURNAL component overlaps a given time range if the condition
    for the corresponding component state specified in the table below
    is satisfied.  The conditions depend on the presence of the
    DTSTART property in the VJOURNAL component and on whether the
    DTSTART is a DATE-TIME or DATE value.  The effective "duration" of
    a VJOURNAL component is 1 day (+P1D) when the DTSTART is a DATE
    value, and 0 seconds when the DTSTART is a DATE-TIME value.

Daboo, et al. Standards Track [Page 92] RFC 4791 CalDAV March 2007

    +----------------------------------------------------+
    | VJOURNAL has the DTSTART property?                 |
    |   +------------------------------------------------+
    |   | DTSTART property is a DATE-TIME value?         |
    |   |   +--------------------------------------------+
    |   |   | Condition to evaluate                      |
    +---+---+--------------------------------------------+
    | Y | Y | (start <= DTSTART)     AND (end > DTSTART) |
    +---+---+--------------------------------------------+
    | Y | N | (start <  DTSTART+P1D) AND (end > DTSTART) |
    +---+---+--------------------------------------------+
    | N | * | FALSE                                      |
    +---+---+--------------------------------------------+
    A VFREEBUSY component overlaps a given time range if the condition
    for the corresponding component state specified in the table below
    is satisfied.  The conditions depend on the presence in the
    VFREEBUSY component of the DTSTART and DTEND properties, and any
    FREEBUSY properties in the absence of DTSTART and DTEND.  Any
    DURATION property is ignored, as it has a special meaning when
    used in a VFREEBUSY component.
    When only FREEBUSY properties are used, each period in each
    FREEBUSY property is compared against the time range, irrespective
    of the type of free busy information (free, busy, busy-tentative,
    busy-unavailable) represented by the property.
    +------------------------------------------------------+
    | VFREEBUSY has both the DTSTART and DTEND properties? |
    |   +--------------------------------------------------+
    |   | VFREEBUSY has the FREEBUSY property?             |
    |   |   +----------------------------------------------+
    |   |   | Condition to evaluate                        |
    +---+---+----------------------------------------------+
    | Y | * | (start <= DTEND) AND (end > DTSTART)         |
    +---+---+----------------------------------------------+
    | N | Y | (start <  freebusy-period-end) AND           |
    |   |   | (end   >  freebusy-period-start)             |
    +---+---+----------------------------------------------+
    | N | N | FALSE                                        |
    +---+---+----------------------------------------------+
    A VALARM component is said to overlap a given time range if the
    following condition holds:
       (start <= trigger-time) AND (end > trigger-time)

Daboo, et al. Standards Track [Page 93] RFC 4791 CalDAV March 2007

 A VALARM component can be defined such that it triggers repeatedly.
 Such a VALARM component is said to overlap a given time range if at
 least one of its triggers overlaps the time range.
    The calendar properties COMPLETED, CREATED, DTEND, DTSTAMP,
    DTSTART, DUE, and LAST-MODIFIED overlap a given time range if the
    following condition holds:
        (start <= date-time) AND (end > date-time)
 Note that if DTEND is not present in a VEVENT, but DURATION is, then
 the test should instead operate on the 'effective' DTEND, i.e.,
 DTSTART+DURATION.  Similarly, if DUE is not present in a VTODO, but
 DTSTART and DURATION are, then the test should instead operate on the
 'effective' DUE, i.e., DTSTART+DURATION.
    The semantic of CALDAV:time-range is not defined for any other
    calendar components and properties.
 Definition:
       <!ELEMENT time-range EMPTY>
       <!ATTLIST time-range start CDATA #IMPLIED
                            end   CDATA #IMPLIED>
       start value: an iCalendar "date with UTC time"
       end value: an iCalendar "date with UTC time"

9.10. CALDAV:calendar-multiget XML Element

 Name:  calendar-multiget
 Namespace:  urn:ietf:params:xml:ns:caldav
 Purpose:  CalDAV report used to retrieve specific calendar object
    resources.
 Description:  See Section 7.9.
 Definition:
       <!ELEMENT calendar-multiget ((DAV:allprop |
                                    DAV:propname |
                                    DAV:prop)?, DAV:href+)>

Daboo, et al. Standards Track [Page 94] RFC 4791 CalDAV March 2007

9.11. CALDAV:free-busy-query XML Element

 Name:  free-busy-query
 Namespace:  urn:ietf:params:xml:ns:caldav
 Purpose:  CalDAV report used to generate a VFREEBUSY to determine
    busy time over a specific time range.
 Description:  See Section 7.10.
 Definition:
       <!ELEMENT free-busy-query (time-range)>

10. Internationalization Considerations

 CalDAV allows internationalized strings to be stored and retrieved
 for the description of calendar collections (see Section 5.2.1).
 The CALDAV:calendar-query REPORT (Section 7.8) includes a text
 searching option controlled by the CALDAV:text-match element, and
 details of character handling are covered in the description of that
 element (see Section 9.7.5).

11. Security Considerations

 HTTP protocol transactions are sent in the clear over the network
 unless protection from snooping is negotiated.  This can be
 accomplished by use of TLS, as defined in [RFC2818].  In particular,
 HTTP Basic authentication MUST NOT be used unless TLS is in effect.
 Servers MUST take adequate precautions to ensure that malicious
 clients cannot consume excessive server resources (CPU, memory, disk,
 etc.) through carefully crafted reports.  For example, a client could
 upload an event with a recurrence rule that specifies a recurring
 event occurring every second for the next 100 years, which would
 result in approximately 3 x 10^9 instances!  A report that asks for
 recurrences to be expanded over that range would likely constitute a
 denial-of-service attack on the server.
 When creating new resources (including calendar collections), clients
 MUST ensure that the resource name (the last path segment of the
 resource URI) assigned to the new resource does not expose any data
 from within the iCalendar resource itself or information about the
 nature of a calendar collection.  This is required to ensure that the
 presence of a specific iCalendar component or nature of components in
 a collection cannot be inferred based on the name of a resource.

Daboo, et al. Standards Track [Page 95] RFC 4791 CalDAV March 2007

 When rolling up free-busy information, more information about a
 user's events is exposed if busy periods overlap or are adjacent
 (this tells the client requesting the free-busy information that the
 calendar owner has at least two events, rather than knowing only that
 the calendar owner has one or more events during the busy period).
 Thus, a conservative approach to calendar data privacy would have
 servers always coalesce such busy periods when they are the same
 type.
 Procedure alarms are a known security risk for either clients or
 servers to handle, particularly when the alarm was created by another
 agent.  Clients and servers are not required to execute such
 procedure alarms.
 Security considerations described in iCalendar [RFC2445] and iTIP
 [RFC2446] are also applicable to CalDAV.
 Beyond these, CalDAV does not raise any security considerations that
 are not present in HTTP [RFC2616] and WebDAV [RFC2518], [RFC3253],
 [RFC3744].

12. IANA Considerations

 This document uses one new URN to identify a new XML namespace.  The
 URN conforms to a registry mechanism described in [RFC3688].

12.1. Namespace Registration

 Registration request for the CalDAV namespace:
 URI: urn:ietf:params:xml:ns:caldav
 Registrant Contact: See the "Authors' Addresses" section of this
 document.
 XML: None.  Namespace URIs do not represent an XML specification.

13. Acknowledgements

 The authors would like to thank the following individuals for
 contributing their ideas and support for writing this specification:
 Michael Arick, Mario Bonin, Chris Bryant, Scott Carr, Andre
 Courtemanche, Mike Douglass, Ted Hardie, Marten den Haring, Jeffrey
 Harris, Sam Hartman, Helge Hess, Jeff McCullough, Alexey Melnikov,
 Dan Mosedale, Brian Moseley, Francois Perrault, Kervin L. Pierre,
 Julian F. Reschke, Wilfredo Sanchez Vega, Mike Shaver, Jari
 Urpalainen, Simon Vaillancourt, and Jim Whitehead.

Daboo, et al. Standards Track [Page 96] RFC 4791 CalDAV March 2007

 The authors would also like to thank the Calendaring and Scheduling
 Consortium for advice with this specification, and for organizing
 interoperability testing events to help refine it.

14. References

14.1. Normative References

 [RFC2119]               Bradner, S., "Key words for use in RFCs to
                         Indicate Requirement Levels", BCP 14,
                         RFC 2119, March 1997.
 [RFC2246]               Dierks, T. and C. Allen, "The TLS Protocol
                         Version 1.0", RFC 2246, January 1999.
 [RFC2445]               Dawson, F. and Stenerson, D., "Internet
                         Calendaring and Scheduling Core Object
                         Specification (iCalendar)", RFC 2445,
                         November 1998.
 [RFC2446]               Silverberg, S., Mansour, S., Dawson, F., and
                         R. Hopson, "iCalendar Transport-Independent
                         Interoperability Protocol (iTIP) Scheduling
                         Events, BusyTime, To-dos and Journal
                         Entries", RFC 2446, November 1998.
 [RFC2518]               Goland, Y., Whitehead, E., Faizi, A., Carter,
                         S., and D. Jensen, "HTTP Extensions for
                         Distributed Authoring -- WEBDAV", RFC 2518,
                         February 1999.
 [RFC2616]               Fielding, R., Gettys, J., Mogul, J., Frystyk,
                         H., Masinter, L., Leach, P., and T. Berners-
                         Lee, "Hypertext Transfer Protocol --
                         HTTP/1.1", RFC 2616, June 1999.
 [RFC2818]               Rescorla, E., "HTTP Over TLS", RFC 2818,
                         May 2000.
 [RFC3253]               Clemm, G., Amsden, J., Ellison, T., Kaler,
                         C., and J. Whitehead, "Versioning Extensions
                         to WebDAV (Web Distributed Authoring and
                         Versioning)", RFC 3253, March 2002.
 [RFC3688]               Mealling, M., "The IETF XML Registry",
                         BCP 81, RFC 3688, January 2004.

Daboo, et al. Standards Track [Page 97] RFC 4791 CalDAV March 2007

 [RFC3744]               Clemm, G., Reschke, J., Sedlar, E., and J.
                         Whitehead, "Web Distributed Authoring and
                         Versioning (WebDAV) Access Control Protocol",
                         RFC 3744, May 2004.
 [RFC4346]               Dierks, T. and E. Rescorla, "The Transport
                         Layer Security (TLS) Protocol Version 1.1",
                         RFC 4346, April 2006.
 [RFC4790]               Newman, C., Duerst, M., and A. Gulbrandsen,
                         "Internet Application Protocol Collation
                         Registry", RFC 4790, March 2007.
 [W3C.REC-xml-20060816]  Paoli, J., Maler, E., Yergeau, F., Sperberg-
                         McQueen, C., and T. Bray, "Extensible Markup
                         Language (XML) 1.0 (Fourth Edition)", World
                         Wide Web Consortium Recommendation REC-xml-
                         20060816, August 2006,
                         <http://www.w3.org/TR/2006/REC-xml-20060816>.

14.2. Informative References

 [RFC2426]               Dawson, F. and T. Howes, "vCard MIME
                         Directory Profile", RFC 2426, September 1998.
 [RFC2739]               Small, T., Hennessy, D., and F. Dawson,
                         "Calendar Attributes for vCard and LDAP",
                         RFC 2739, January 2000.
 [RFC4331]               Korver, B. and L. Dusseault, "Quota and Size
                         Properties for Distributed Authoring and
                         Versioning (DAV) Collections", RFC 4331,
                         February 2006.
 [RFC4511]               Sermersheim, J., "Lightweight Directory
                         Access Protocol (LDAP): The Protocol",
                         RFC 4511, June 2006.
 [rfc2518bis]            Dusseault, L., "HTTP Extensions for
                         Distributed Authoring - WebDAV", Work
                         in Progress, December 2006.

Daboo, et al. Standards Track [Page 98] RFC 4791 CalDAV March 2007

Appendix A. CalDAV Method Privilege Table (Normative)

 The following table extends the WebDAV Method Privilege Table
 specified in Appendix B of [RFC3744].
 +------------+------------------------------------------------------+
 | METHOD     | PRIVILEGES                                           |
 +------------+------------------------------------------------------+
 | MKCALENDAR | DAV:bind                                             |
 | REPORT     | DAV:read or CALDAV:read-free-busy (on all referenced |
 |            | resources)                                           |
 +------------+------------------------------------------------------+

Appendix B. Calendar Collections Used in the Examples

 This appendix shows the calendar object resources contained in the
 calendar collection queried in the examples throughout this document.
 The content of the calendar collection is being shown as if it were
 returned by a CALDAV:calendar-query REPORT request designed to return
 all the calendar data in the collection:
 >> 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/>
  </D:prop>
  <C:filter>
    <C:comp-filter name="VCALENDAR"/>
  </C:filter>
 </C:calendar-query>
 >> Response <<
 HTTP/1.1 207 Multi-Status
 Content-Type: application/xml; charset="utf-8"
 Content-Length: xxxx

Daboo, et al. Standards Track [Page 99] RFC 4791 CalDAV March 2007

 <?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/abcd1.ics</D:href>
     <D:propstat>
       <D:prop>
         <D:getetag>"fffff-abcd1"</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:20060206T001102Z
 DTSTART;TZID=US/Eastern:20060102T100000
 DURATION:PT1H
 SUMMARY:Event #1
 Description:Go Steelers!
 UID:74855313FA803DA593CD579A@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/abcd2.ics</D:href>
     <D:propstat>

Daboo, et al. Standards Track [Page 100] RFC 4791 CalDAV March 2007

       <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>
       <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>

Daboo, et al. Standards Track [Page 101] RFC 4791 CalDAV March 2007

     <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
 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/abcd4.ics</D:href>
     <D:propstat>
       <D:prop>

Daboo, et al. Standards Track [Page 102] RFC 4791 CalDAV March 2007

         <D:getetag>"fffff-abcd4"</D:getetag>
         <C:calendar-data>BEGIN:VCALENDAR
 VERSION:2.0
 PRODID:-//Example Corp.//CalDAV Client//EN
 BEGIN:VTODO
 DTSTAMP:20060205T235335Z
 DUE;VALUE=DATE:20060104
 STATUS:NEEDS-ACTION
 SUMMARY:Task #1
 UID:DDDEEB7915FA61233B861457@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:response>
     <D:href>http://cal.example.com/bernard/work/abcd5.ics</D:href>
     <D:propstat>
       <D:prop>
         <D:getetag>"fffff-abcd5"</D:getetag>
         <C:calendar-data>BEGIN:VCALENDAR
 VERSION:2.0
 PRODID:-//Example Corp.//CalDAV Client//EN
 BEGIN:VTODO
 DTSTAMP:20060205T235300Z
 DUE;VALUE=DATE:20060106
 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>

Daboo, et al. Standards Track [Page 103] RFC 4791 CalDAV March 2007

   </D:response>
   <D:response>
     <D:href>http://cal.example.com/bernard/work/abcd6.ics</D:href>
     <D:propstat>
       <D:prop>
         <D:getetag>"fffff-abcd6"</D:getetag>
         <C:calendar-data>BEGIN:VCALENDAR
 VERSION:2.0
 PRODID:-//Example Corp.//CalDAV Client//EN
 BEGIN:VTODO
 COMPLETED:20051223T122322Z
 DTSTAMP:20060205T235400Z
 DUE;VALUE=DATE:20051225
 LAST-MODIFIED:20060205T235308Z
 SEQUENCE:1
 STATUS:COMPLETED
 SUMMARY:Task #3
 UID:E10BA47467C5C69BB74E8722@example.com
 END:VTODO
 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/abcd7.ics</D:href>
     <D:propstat>
       <D:prop>
         <D:getetag>"fffff-abcd7"</D:getetag>
         <C:calendar-data>BEGIN:VCALENDAR
 VERSION:2.0
 PRODID:-//Example Corp.//CalDAV Client//EN
 BEGIN:VTODO
 DTSTAMP:20060205T235600Z
 DUE;VALUE=DATE:20060101
 LAST-MODIFIED:20060205T235308Z
 SEQUENCE:1
 STATUS:CANCELLED
 SUMMARY:Task #4
 UID:E10BA47467C5C69BB74E8725@example.com
 END:VTODO
 END:VCALENDAR
 </C:calendar-data>
       </D:prop>
       <D:status>HTTP/1.1 200 OK</D:status>

Daboo, et al. Standards Track [Page 104] RFC 4791 CalDAV March 2007

     </D:propstat>
   </D:response>
   <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:20060101T000000Z
 DTEND:20060108T000000Z
 FREEBUSY:20050531T230000Z/20050601T010000Z
 FREEBUSY;FBTYPE=BUSY-TENTATIVE:20060102T100000Z/20060102T120000Z
 FREEBUSY:20060103T100000Z/20060103T120000Z
 FREEBUSY:20060104T100000Z/20060104T120000Z
 FREEBUSY;FBTYPE=BUSY-UNAVAILABLE:20060105T100000Z/20060105T120000Z
 FREEBUSY:20060106T100000Z/20060106T120000Z
 END:VFREEBUSY
 END:VCALENDAR
 </C:calendar-data>
       </D:prop>
       <D:status>HTTP/1.1 200 OK</D:status>
     </D:propstat>
   </D:response>
 </D:multistatus>

Daboo, et al. Standards Track [Page 105] RFC 4791 CalDAV March 2007

Authors' Addresses

 Cyrus Daboo
 Apple Inc.
 1 Infinite Loop
 Cupertino, CA  95014
 USA
 EMail: cyrus@daboo.name
 URI:   http://www.apple.com/
 Bernard Desruisseaux
 Oracle Corporation
 600 Blvd. de Maisonneuve West
 Suite 1900
 Montreal, QC  H3A 3J2
 CANADA
 EMail: bernard.desruisseaux@oracle.com
 URI:   http://www.oracle.com/
 Lisa Dusseault
 CommerceNet
 169 University Ave.
 Palo Alto, CA  94301
 USA
 EMail: ldusseault@commerce.net
 URI:   http://commerce.net/

Daboo, et al. Standards Track [Page 106] RFC 4791 CalDAV March 2007

Full Copyright Statement

 Copyright (C) The IETF Trust (2007).
 This document is subject to the rights, licenses and restrictions
 contained in BCP 78, and except as set forth therein, the authors
 retain all their rights.
 This document and the information contained herein are provided on an
 "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS
 OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY, THE IETF TRUST AND
 THE INTERNET ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS
 OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF
 THE INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED
 WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.

Intellectual Property

 The IETF takes no position regarding the validity or scope of any
 Intellectual Property Rights or other rights that might be claimed to
 pertain to the implementation or use of the technology described in
 this document or the extent to which any license under such rights
 might or might not be available; nor does it represent that it has
 made any independent effort to identify any such rights.  Information
 on the procedures with respect to rights in RFC documents can be
 found in BCP 78 and BCP 79.
 Copies of IPR disclosures made to the IETF Secretariat and any
 assurances of licenses to be made available, or the result of an
 attempt made to obtain a general license or permission for the use of
 such proprietary rights by implementers or users of this
 specification can be obtained from the IETF on-line IPR repository at
 http://www.ietf.org/ipr.
 The IETF invites any interested party to bring to its attention any
 copyrights, patents or patent applications, or other proprietary
 rights that may cover technology that may be required to implement
 this standard.  Please address the information to the IETF at
 ietf-ipr@ietf.org.

Acknowledgement

 Funding for the RFC Editor function is currently provided by the
 Internet Society.

Daboo, et al. Standards Track [Page 107]

/data/webs/external/dokuwiki/data/pages/rfc/rfc4791.txt · Last modified: 2007/03/12 18:51 by 127.0.0.1

Donate Powered by PHP Valid HTML5 Valid CSS Driven by DokuWiki