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rfc:rfc6352

Internet Engineering Task Force (IETF) C. Daboo Request for Comments: 6352 Apple Category: Standards Track August 2011 ISSN: 2070-1721

                    CardDAV: vCard Extensions to
         Web Distributed Authoring and Versioning (WebDAV)

Abstract

 This document defines extensions to the Web Distributed Authoring and
 Versioning (WebDAV) protocol to specify a standard way of accessing,
 managing, and sharing contact information based on the vCard format.

Status of This Memo

 This is an Internet Standards Track document.
 This document is a product of the Internet Engineering Task Force
 (IETF).  It represents the consensus of the IETF community.  It has
 received public review and has been approved for publication by the
 Internet Engineering Steering Group (IESG).  Further information on
 Internet Standards is available in Section 2 of RFC 5741.
 Information about the current status of this document, any errata,
 and how to provide feedback on it may be obtained at
 http://www.rfc-editor.org/info/rfc6352.

Copyright Notice

 Copyright (c) 2011 IETF Trust and the persons identified as the
 document authors.  All rights reserved.
 This document is subject to BCP 78 and the IETF Trust's Legal
 Provisions Relating to IETF Documents
 (http://trustee.ietf.org/license-info) in effect on the date of
 publication of this document.  Please review these documents
 carefully, as they describe your rights and restrictions with respect
 to this document.  Code Components extracted from this document must
 include Simplified BSD License text as described in Section 4.e of
 the Trust Legal Provisions and are provided without warranty as
 described in the Simplified BSD License.
 This document may contain material from IETF Documents or IETF
 Contributions published or made publicly available before November
 10, 2008.  The person(s) controlling the copyright in some of this
 material may not have granted the IETF Trust the right to allow

Daboo Standards Track [Page 1] RFC 6352 CardDAV August 2011

 modifications of such material outside the IETF Standards Process.
 Without obtaining an adequate license from the person(s) controlling
 the copyright in such materials, this document may not be modified
 outside the IETF Standards Process, and derivative works of it may
 not be created outside the IETF Standards Process, except to format
 it for publication as an RFC or to translate it into languages other
 than English.

Table of Contents

 1.  Introduction and Overview  . . . . . . . . . . . . . . . . . .  4
 2.  Conventions  . . . . . . . . . . . . . . . . . . . . . . . . .  5
 3.  Requirements Overview  . . . . . . . . . . . . . . . . . . . .  6
 4.  Address Book Data Model  . . . . . . . . . . . . . . . . . . .  7
   4.1.  Address Book Server  . . . . . . . . . . . . . . . . . . .  7
 5.  Address Book Resources . . . . . . . . . . . . . . . . . . . .  7
   5.1.  Address Object Resources . . . . . . . . . . . . . . . . .  7
     5.1.1.  Data Type Conversion . . . . . . . . . . . . . . . . .  8
       5.1.1.1.  Additional Precondition for GET  . . . . . . . . .  8
   5.2.  Address Book Collections . . . . . . . . . . . . . . . . .  9
 6.  Address Book Feature . . . . . . . . . . . . . . . . . . . . . 10
   6.1.  Address Book Support . . . . . . . . . . . . . . . . . . . 10
     6.1.1.  Example: Using OPTIONS for the Discovery of
             Support for CardDAV  . . . . . . . . . . . . . . . . . 10
   6.2.  Address Book Properties  . . . . . . . . . . . . . . . . . 10
     6.2.1.  CARDDAV:addressbook-description Property . . . . . . . 10
     6.2.2.  CARDDAV:supported-address-data Property  . . . . . . . 11
     6.2.3.  CARDDAV:max-resource-size Property . . . . . . . . . . 12
   6.3.  Creating Resources . . . . . . . . . . . . . . . . . . . . 13
     6.3.1.  Extended MKCOL Method  . . . . . . . . . . . . . . . . 13
       6.3.1.1.  Example - Successful MKCOL Request . . . . . . . . 14
     6.3.2.  Creating Address Object Resources  . . . . . . . . . . 15
       6.3.2.1.  Additional Preconditions for PUT, COPY, and
                 MOVE . . . . . . . . . . . . . . . . . . . . . . . 16
       6.3.2.2.  Non-Standard vCard Properties and Parameters . . . 17
       6.3.2.3.  Address Object Resource Entity Tag . . . . . . . . 18
 7.  Address Book Access Control  . . . . . . . . . . . . . . . . . 18
   7.1.  Additional Principal Properties  . . . . . . . . . . . . . 18
     7.1.1.  CARDDAV:addressbook-home-set Property  . . . . . . . . 19
     7.1.2.  CARDDAV:principal-address Property . . . . . . . . . . 19
 8.  Address Book Reports . . . . . . . . . . . . . . . . . . . . . 20
   8.1.  REPORT Method  . . . . . . . . . . . . . . . . . . . . . . 20
   8.2.  Ordinary Collections . . . . . . . . . . . . . . . . . . . 21
   8.3.  Searching Text: Collations . . . . . . . . . . . . . . . . 21
     8.3.1.  CARDDAV:supported-collation-set Property . . . . . . . 22
   8.4.  Partial Retrieval  . . . . . . . . . . . . . . . . . . . . 23
   8.5.  Non-Standard Properties and Parameters . . . . . . . . . . 23

Daboo Standards Track [Page 2] RFC 6352 CardDAV August 2011

   8.6.  CARDDAV:addressbook-query Report . . . . . . . . . . . . . 23
     8.6.1.  Limiting Results . . . . . . . . . . . . . . . . . . . 25
     8.6.2.  Truncation of Results  . . . . . . . . . . . . . . . . 25
     8.6.3.  Example: Partial Retrieval of vCards Matching
             NICKNAME . . . . . . . . . . . . . . . . . . . . . . . 26
     8.6.4.  Example: Partial Retrieval of vCards Matching a
             Full Name or Email Address . . . . . . . . . . . . . . 27
     8.6.5.  Example: Truncated Results . . . . . . . . . . . . . . 29
   8.7.  CARDDAV:addressbook-multiget Report  . . . . . . . . . . . 31
     8.7.1.  Example: CARDDAV:addressbook-multiget Report . . . . . 32
     8.7.2.  Example: CARDDAV:addressbook-multiget Report . . . . . 33
 9.  Client Guidelines  . . . . . . . . . . . . . . . . . . . . . . 34
   9.1.  Restrict the Properties Returned . . . . . . . . . . . . . 34
   9.2.  Avoiding Lost Updates  . . . . . . . . . . . . . . . . . . 35
   9.3.  Client Configuration . . . . . . . . . . . . . . . . . . . 35
   9.4.  Finding Other Users' Address Books . . . . . . . . . . . . 35
 10. XML Element Definitions  . . . . . . . . . . . . . . . . . . . 36
   10.1. CARDDAV:addressbook XML Element  . . . . . . . . . . . . . 36
   10.2. CARDDAV:supported-collation XML Element  . . . . . . . . . 36
   10.3. CARDDAV:addressbook-query XML Element  . . . . . . . . . . 37
   10.4. CARDDAV:address-data XML Element . . . . . . . . . . . . . 37
     10.4.1. CARDDAV:allprop XML Element  . . . . . . . . . . . . . 39
     10.4.2. CARDDAV:prop XML Element . . . . . . . . . . . . . . . 39
   10.5. CARDDAV:filter XML Element . . . . . . . . . . . . . . . . 40
     10.5.1. CARDDAV:prop-filter XML Element  . . . . . . . . . . . 40
     10.5.2. CARDDAV:param-filter XML Element . . . . . . . . . . . 41
     10.5.3. CARDDAV:is-not-defined XML Element . . . . . . . . . . 42
     10.5.4. CARDDAV:text-match XML Element . . . . . . . . . . . . 42
   10.6. CARDDAV:limit XML Element  . . . . . . . . . . . . . . . . 43
     10.6.1. CARDDAV:nresults XML Element . . . . . . . . . . . . . 44
   10.7. CARDDAV:addressbook-multiget XML Element . . . . . . . . . 44
 11. Service Discovery via SRV Records  . . . . . . . . . . . . . . 45
 12. Internationalization Considerations  . . . . . . . . . . . . . 45
 13. Security Considerations  . . . . . . . . . . . . . . . . . . . 45
 14. IANA Consideration . . . . . . . . . . . . . . . . . . . . . . 46
   14.1. Namespace Registration . . . . . . . . . . . . . . . . . . 46
 15. Acknowledgments  . . . . . . . . . . . . . . . . . . . . . . . 46
 16. References . . . . . . . . . . . . . . . . . . . . . . . . . . 47
   16.1. Normative References . . . . . . . . . . . . . . . . . . . 47
   16.2. Informative References . . . . . . . . . . . . . . . . . . 48

Daboo Standards Track [Page 3] RFC 6352 CardDAV August 2011

1. Introduction and Overview

 Address books containing contact information are a key component of
 personal information management tools, such as email, calendaring and
 scheduling, and instant messaging clients.  To date several protocols
 have been used for remote access to contact data, including the
 Lightweight Directory Access Protocol (LDAP) [RFC4510], Internet
 Message Support Protocol [IMSP], and Application Configuration Access
 Protocol (ACAP) [RFC2244], together with SyncML used for
 synchronization of such data.
 WebDAV [RFC4918] offers a number of advantages as a framework or
 basis for address book access and management.  Most of these
 advantages boil down to a significant reduction in the costs of
 design, implementation, interoperability testing, and deployment.
 The key features of address book support with WebDAV are:
 1.  Ability to use multiple address books with hierarchical layout.
 2.  Ability to control access to individual address books and address
     entries as per WebDAV Access Control List (ACL) [RFC3744].
 3.  Principal collections can be used to enumerate and query other
     users on the system as per WebDAV ACL [RFC3744].
 4.  Server-side searching of address data, avoiding the need for
     clients to download an entire address book in order to do a quick
     address 'expansion' operation.
 5.  Well-defined internationalization support through WebDAV's use of
     XML.
 6.  Use of vCards [RFC2426] for well-defined address schema to
     enhance client interoperability.
 7.  Many limited clients (e.g., mobile devices) contain an HTTP stack
     that makes implementing WebDAV much easier than other protocols.
 The key disadvantage of address book support in WebDAV is:
 1.  Lack of change notification.  Many of the alternative protocols
     also lack this ability.  However, an extension for push
     notifications could easily be developed.
 vCard is a MIME directory profile aimed at encapsulating personal
 addressing and contact information about people.  The specification
 of vCard was originally done by the Versit consortium, with a

Daboo Standards Track [Page 4] RFC 6352 CardDAV August 2011

 subsequent 3.0 version standardized by the IETF [RFC2426]. vCard is
 in widespread use in email clients and mobile devices as a means of
 encapsulating address information for transport via email or for
 import/export and synchronization operations.
 An update to vCard -- vCard v4 -- is currently being developed
 [RFC6350] and is compatible with this specification.

2. 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 15 of [RFC4918].
 This document uses XML DTD fragments ([W3C.REC-xml-20081126], Section
 3.2) as a purely notational convention.  WebDAV request and response
 bodies cannot be validated by a DTD due to the specific extensibility
 rules defined in Section 17 of [RFC4918] and due to the fact that all
 XML elements defined by that specification use the XML namespace name
 "DAV:".  In particular:
 1.  Element names use the "DAV:" namespace.
 2.  Element ordering is irrelevant unless explicitly stated.
 3.  Extension elements (elements not already defined as valid child
     elements) may be added anywhere, except when explicitly stated
     otherwise.
 4.  Extension attributes (attributes not already defined as valid for
     this element) may be added anywhere, except when explicitly
     stated otherwise.
 The namespace "urn:ietf:params:xml:ns:carddav" is reserved for the
 XML elements defined in this specification, its revisions, and
 related CardDAV specifications.  XML elements defined by individual
 implementations MUST NOT use the "urn:ietf:params:xml:ns:carddav"
 namespace, and instead should use a namespace that they control.
 When XML element types in the namespaces "DAV:" and
 "urn:ietf:params:xml:ns:carddav" are referenced in this document
 outside of the context of an XML fragment, the strings "DAV:" and
 "CARDDAV:" will be prefixed to the element types, respectively.

Daboo Standards Track [Page 5] RFC 6352 CardDAV August 2011

 This document inherits, and sometimes extends, DTD productions from
 Section 14 of [RFC4918].
 Also, note that some CardDAV 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.

3. Requirements Overview

 This section lists what functionality is required of a CardDAV
 server.  To advertise support for CardDAV, a server:
 o  MUST support vCard v3 [RFC2426] as a media type for the address
    object resource format;
 o  MUST support WebDAV Class 3 [RFC4918];
 o  MUST support WebDAV ACL [RFC3744];
 o  MUST support secure transport as defined in [RFC2818] using
    Transport Layer Security (TLS) [RFC5246] and using the certificate
    validation procedures described in [RFC5280];
 o  MUST support ETags [RFC2616] with additional requirements
    specified in Section 6.3.2.3 of this document;
 o  MUST support all address book reports defined in Section 8 of this
    document; and
 o  MUST advertise support on all address book collections and address
    object resources for the address book reports in the
    DAV:supported-report-set property, as defined in Versioning
    Extensions to WebDAV [RFC3253].
 In addition, a server:
 o  SHOULD support vCard v4 [RFC6350] as a media type for the address
    object resource format;
 o  SHOULD support the extended MKCOL method [RFC5689] to create
    address book collections as defined in Section 6.3.1 of this
    document.
 o  SHOULD support the DAV:current-user-principal-URL property as
    defined in [RFC5397] to give clients a fast way to locate user
    principals.

Daboo Standards Track [Page 6] RFC 6352 CardDAV August 2011

4. Address Book Data Model

 As a brief overview, a CardDAV address book is modeled as a WebDAV
 collection with a well-defined structure; each of these address book
 collections contains a number of resources representing address
 objects as their direct child resources.  Each resource representing
 an address object is called an "address object resource".  Each
 address object resource and each address book collection can be
 individually locked and have individual WebDAV properties.
 Requirements derived from this model are provided in Sections 5.1 and
 5.2.

4.1. Address Book Server

 A CardDAV server is an address-aware engine combined with a WebDAV
 server.  The server may include address data in some parts of its URL
 namespace and non-address data in other parts.
 A WebDAV server can advertise itself as a CardDAV server if it
 supports the functionality defined in this specification at any point
 within the root of its repository.  That might mean that address data
 is spread throughout the repository and mixed with non-address data
 in nearby collections (e.g., address data may be found in /lisa/
 addressbook/ as well as in /bernard/addressbook/, and non-address
 data in /lisa/calendars/).  Or, it might mean that address data can
 be found only in certain sections of the repository (e.g.,
 /addressbooks/user/).  Address book features are only required in the
 repository sections that are or contain address objects.  So, a
 repository confining address data to the /carddav/ collection would
 only need to support the CardDAV required features within that
 collection.
 The CardDAV server is the canonical location for address data and
 state information.  Clients may submit requests to change data or
 download data.  Clients may store address objects offline and attempt
 to synchronize at a later time.  Address data on the server can
 change between the time of last synchronization and when attempting
 an update, as address book collections may be shared and accessible
 via multiple clients.  Entity tags and locking help this work.

5. Address Book Resources

5.1. Address Object Resources

 This specification uses vCard as the default format for address or
 contact information being stored on the server.  However, this
 specification does allow other formats for address data provided that
 the server advertises support for those additional formats as

Daboo Standards Track [Page 7] RFC 6352 CardDAV August 2011

 described below.  The requirements in this section pertain to vCard
 address data or formats that follow the semantics of vCard data.
 Address object resources contained in address book collections MUST
 contain a single vCard component only.
 vCard components in an address book collection MUST have a UID
 property value that MUST be unique in the scope of the address book
 collection in which it is contained.

5.1.1. Data Type Conversion

 Servers might support more than one primary media type for address
 object resources, for example, vCard v3.0 and vCard v4.0.  In such
 cases, servers have to accept all media types that they advertise via
 the CARDDAV:supported-address-data WebDAV property (see
 Section 6.2.2).
 However, clients can use standard HTTP content negotiation behavior
 (the Accept request header defined in Section 14.1 of [RFC2616]) to
 request that an address object resource's data be returned in a
 specific media type format.  For example, a client merely capable of
 handling vCard v3.0 would only want to have address object resources
 returned in v3.0 format.
 Additionally, REPORT requests, defined later in this specification,
 allow for the return of address object resource data within an XML
 response body.  Again, the client can use content negotiation to
 request that data be returned in a specific media type by specifying
 appropriate attributes on the CARDDAV:address-data XML element used
 in the request body (see Section 10.4).
 In some cases, it might not be possible for a server to convert from
 one media type to another.  When that happens, the server MUST return
 the CARDDAV:supported-address-data-conversion precondition (see
 below) in the response body (when the failure to convert applies to
 the entire response) or use that same precondition code in the
 DAV:response XML element in the response for the targeted address
 object resource when one of the REPORTs defined below is used.  See
 Section 8.7.2 for an example of this.

5.1.1.1. Additional Precondition for GET

 This specification creates additional preconditions for the GET
 method.

Daboo Standards Track [Page 8] RFC 6352 CardDAV August 2011

 The new precondition is:
    (CARDDAV:supported-address-data-conversion): The resource targeted
    by the GET request can be converted to the media type specified in
    the Accept request header included with the request.

5.2. Address Book Collections

 Address book collections appear to clients as a WebDAV collection
 resource, identified by a URL.  An address book collection MUST
 report the DAV:collection and CARDDAV:addressbook XML elements in the
 value of the DAV:resourcetype property.  The element type declaration
 for CARDDAV:addressbook is:
     <!ELEMENT addressbook EMPTY>
 An address book collection can be created through provisioning (e.g.,
 automatically created when a user's account is provisioned), or it
 can be created with the extended MKCOL method (see Section 6.3.1).
 This can be used by a user to create additional address books (e.g.,
 "soccer team members") or for users to share an address book (e.g.,
 "sales team contacts").  However, note that this document doesn't
 define what extra address book collections are for.  Users must rely
 on non-standard cues to find out what an address book collection is
 for, or use the CARDDAV:addressbook-description property defined in
 Section 6.2.1 to provide such a cue.
 The following restrictions are applied to the resources within an
 address book collection:
 a.  Address book collections MUST only contain address object
     resources and collections that are not address book collections.
     That is, the only "top-level" non-collection resources allowed in
     an address book collection are address object resources.  This
     ensures that address book clients do not have to deal with non-
     address data in an address book collection, though they do have
     to distinguish between address object resources and collections
     when using standard WebDAV techniques to examine the contents of
     a collection.
 b.  Collections contained in address book collections MUST NOT
     contain address book collections at any depth.  That is,
     "nesting" of address book collections within other address book
     collections at any depth is not allowed.  This specification does
     not define how collections contained in an address book
     collection are used or how they relate to any address object
     resources contained in the address book collection.

Daboo Standards Track [Page 9] RFC 6352 CardDAV August 2011

 Multiple address book collections MAY be children of the same
 collection.

6. Address Book Feature

6.1. Address Book Support

 A server supporting the features described in this document MUST
 include "addressbook" as a field in the DAV response header from an
 OPTIONS request on any resource that supports any address book
 properties, reports, or methods.  A value of "addressbook" in the DAV
 response header MUST indicate that the server supports all MUST level
 requirements and REQUIRED features specified in this document.

6.1.1. Example: Using OPTIONS for the Discovery of Support for CardDAV

 >> Request <<
 OPTIONS /addressbooks/users/ HTTP/1.1
 Host: addressbook.example.com
 >> Response <<
 HTTP/1.1 200 OK
 Allow: OPTIONS, GET, HEAD, POST, PUT, DELETE, TRACE, COPY, MOVE
 Allow: MKCOL, PROPFIND, PROPPATCH, LOCK, UNLOCK, REPORT, ACL
 DAV: 1, 2, 3, access-control, addressbook
 DAV: extended-mkcol
 Date: Sat, 11 Nov 2006 09:32:12 GMT
 Content-Length: 0
 In this example, the OPTIONS response indicates that the server
 supports CardDAV in this namespace; therefore, the '/addressbooks/
 users/' collection may be used as a parent for address book
 collections as the extended MKCOL method is available and as a
 possible target for REPORT requests for address book reports.

6.2. Address Book Properties

6.2.1. CARDDAV:addressbook-description Property

 Name:  addressbook-description
 Namespace:  urn:ietf:params:xml:ns:carddav
 Purpose:  Provides a human-readable description of the address book
    collection.

Daboo Standards Track [Page 10] RFC 6352 CardDAV August 2011

 Value:  Any text.
 Protected:  SHOULD NOT be protected so that users can specify a
    description.
 COPY/MOVE behavior:  This property value SHOULD be preserved in COPY
    and MOVE operations.
 allprop behavior:  SHOULD NOT be returned by a PROPFIND DAV:allprop
    request.
 Description:  This property contains a description of the address
    book collection that is suitable for presentation to a user.  The
    xml:lang attribute can be used to add a language tag for the value
    of this property.
 Definition:
     <!ELEMENT addressbook-description (#PCDATA)>
     <!-- PCDATA value: string -->
 Example:
     <C:addressbook-description xml:lang="fr-CA"
        xmlns:C="urn:ietf:params:xml:ns:carddav"
     >Adresses de Oliver Daboo</C:addressbook-description>

6.2.2. CARDDAV:supported-address-data Property

 Name:  supported-address-data
 Namespace:  urn:ietf:params:xml:ns:carddav
 Purpose:  Specifies what media types are allowed for address object
    resources in an address book collection.
 Protected:  MUST be protected as it indicates the level of support
    provided by the server.
 COPY/MOVE behavior:  This property value MUST be preserved in COPY
    and MOVE operations.
 allprop behavior:  SHOULD NOT be returned by a PROPFIND DAV:allprop
    request.
 Description:  The CARDDAV:supported-address-data property is used to
    specify the media type supported for the address object resources
    contained in a given address book collection (e.g., vCard version

Daboo Standards Track [Page 11] RFC 6352 CardDAV August 2011

    3.0).  Any attempt by the client to store address object resources
    with a media type not listed in this property MUST result in an
    error, with the CARDDAV:supported-address-data precondition
    (Section 6.3.2.1) being violated.  In the absence of this
    property, the server MUST only accept data with the media type
    "text/vcard" and vCard version 3.0, and clients can assume that is
    all the server will accept.
 Definition:
     <!ELEMENT supported-address-data (address-data-type+)>
     <!ELEMENT address-data-type EMPTY>
     <!ATTLIST address-data-type content-type CDATA "text/vcard"
                           version CDATA "3.0">
     <!-- content-type value: a MIME media type -->
     <!-- version value: a version string -->
 Example:
     <C:supported-address-data
        xmlns:C="urn:ietf:params:xml:ns:carddav">
       <C:address-data-type content-type="text/vcard" version="3.0"/>
     </C:supported-address-data>

6.2.3. CARDDAV:max-resource-size Property

 Name:  max-resource-size
 Namespace:  urn:ietf:params:xml:ns:carddav
 Purpose:  Provides a numeric value indicating the maximum size in
    octets of a resource that the server is willing to accept when an
    address object resource is stored in an address book collection.
 Value:  Any text representing a numeric value.
 Protected:  MUST be protected as it indicates limits provided by the
    server.
 COPY/MOVE behavior:  This property value MUST be preserved in COPY
    and MOVE operations.
 allprop behavior:  SHOULD NOT be returned by a PROPFIND DAV:allprop
    request.

Daboo Standards Track [Page 12] RFC 6352 CardDAV August 2011

 Description:  The CARDDAV: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 an address object resource is
    stored in an address book collection.  Any attempt to store an
    address book object resource exceeding this size MUST result in an
    error, with the CARDDAV:max-resource-size precondition
    (Section 6.3.2.1) 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 decimal integer) -->
 Example:
     <C:max-resource-size xmlns:C="urn:ietf:params:xml:ns:carddav"
     >102400</C:max-resource-size>

6.3. Creating Resources

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

6.3.1. Extended MKCOL Method

 An HTTP request using the extended MKCOL method [RFC5689] can be used
 to create a new address book collection resource.  A server MAY
 restrict address book collection creation to particular collections.
 To create an address book, the client sends an extended MKCOL request
 to the server and in the body of the request sets the
 DAV:resourcetype property to the resource type for an address book
 collection as defined in Section 5.2.
 Support for creating address books on the server is only RECOMMENDED
 and not REQUIRED because some address book stores only support one
 address book per user (or principal), and those are typically pre-
 created for each account.  However, servers and clients are strongly
 encouraged to support address book creation whenever possible to
 allow users to create multiple address book collections to help
 organize their data better.

Daboo Standards Track [Page 13] RFC 6352 CardDAV August 2011

 The DAV:displayname property can be used for a human-readable name of
 the address book.  Clients can either specify the value of the
 DAV:displayname property in the request body of the extended MKCOL
 request or, alternatively, issue a PROPPATCH request to change the
 DAV:displayname property to the appropriate value immediately after
 using the extended MKCOL request.  When displaying address book
 collections to users, clients SHOULD check the DAV:displayname
 property and use that value as the name of the address book.  In the
 event that the DAV:displayname property is not set, the client MAY
 use the last part of the address book collection URI as the name;
 however, that path segment may be "opaque" and not represent any
 meaningful human-readable text.

6.3.1.1. Example - Successful MKCOL Request

 This example creates an address book collection called /home/lisa/
 addressbook/ on the server addressbook.example.com with specific
 values for the properties DAV:resourcetype, DAV:displayname, and
 CARDDAV:addressbook-description.
 >> Request <<
 MKCOL /home/lisa/addressbook/ HTTP/1.1
 Host: addressbook.example.com
 Content-Type: text/xml; charset="utf-8"
 Content-Length: xxx
 <?xml version="1.0" encoding="utf-8" ?>
 <D:mkcol xmlns:D="DAV:"
               xmlns:C="urn:ietf:params:xml:ns:carddav">
   <D:set>
     <D:prop>
       <D:resourcetype>
         <D:collection/>
         <C:addressbook/>
       </D:resourcetype>
       <D:displayname>Lisa's Contacts</D:displayname>
       <C:addressbook-description xml:lang="en"
 >My primary address book.</C:addressbook-description>
     </D:prop>
   </D:set>
 </D:mkcol>

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 >> Response <<
 HTTP/1.1 201 Created
 Cache-Control: no-cache
 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:mkcol-response xmlns:D="DAV:"
               xmlns:C="urn:ietf:params:xml:ns:carddav">
   <D:propstat>
     <D:prop>
       <D:resourcetype/>
       <D:displayname/>
       <C:addressbook-description/>
     </D:prop>
     <D:status>HTTP/1.1 200 OK</D:status>
   </D:propstat>
 </D:mkcol-response>

6.3.2. Creating Address Object Resources

 Clients populate address book collections with address object
 resources.  The URL for each address object resource is entirely
 arbitrary and does not need to bear a specific relationship (but
 might) to the address object resource's vCard properties or other
 metadata.  New address 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 address object resource.
 When servers create new resources, it's not hard for the server to
 choose a unique URL.  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 one
 isn't created with a name collision.  However, there is an HTTP
 feature to mitigate this.  If the client intends to create a new
 address resource, the client SHOULD use the HTTP 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" header ensures that the client will not inadvertently
 overwrite an existing resource even if the last path segment turned
 out to already be used.

Daboo Standards Track [Page 15] RFC 6352 CardDAV August 2011

 >> Request <<
 PUT /lisa/addressbook/newvcard.vcf HTTP/1.1
 If-None-Match: *
 Host: addressbook.example.com
 Content-Type: text/vcard
 Content-Length: xxx
 BEGIN:VCARD
 VERSION:3.0
 FN:Cyrus Daboo
 N:Daboo;Cyrus
 ADR;TYPE=POSTAL:;2822 Email HQ;Suite 2821;RFCVille;PA;15213;USA
 EMAIL;TYPE=INTERNET,PREF:cyrus@example.com
 NICKNAME:me
 NOTE:Example VCard.
 ORG:Self Employed
 TEL;TYPE=WORK,VOICE:412 605 0499
 TEL;TYPE=FAX:412 605 0705
 URL:http://www.example.com
 UID:1234-5678-9000-1
 END:VCARD
 >> Response <<
 HTTP/1.1 201 Created
 Date: Thu, 02 Sep 2004 16:53:32 GMT
 Content-Length: 0
 ETag: "123456789-000-111"
 The request to change an existing address object resource without
 overwriting a change made on the server uses a specific ETag in an
 "If-Match" header, rather than the "If-None-Match" header.
 File names for vCards are commonly suffixed by ".vcf", and clients
 may choose to use the same convention for URLs.

6.3.2.1. Additional Preconditions for PUT, COPY, and MOVE

 This specification creates additional preconditions for the PUT,
 COPY, and MOVE methods.  These preconditions apply:
 o  When a PUT operation of an address object resource into an address
    book collection occurs.
 o  When a COPY or MOVE operation of an address object resource into
    an address book collection occurs.

Daboo Standards Track [Page 16] RFC 6352 CardDAV August 2011

 The new preconditions are:
    (CARDDAV:supported-address-data): The resource submitted in the
    PUT request, or targeted by a COPY or MOVE request, MUST be a
    supported media type (i.e., vCard) for address object resources.
    (CARDDAV:valid-address-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 vCard
    data).
    (CARDDAV:no-uid-conflict): The resource submitted in the PUT
    request, or targeted by a COPY or MOVE request, MUST NOT specify a
    vCard UID property value already in use in the targeted address
    book collection or overwrite an existing address 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)>
    (CARDDAV:addressbook-collection-location-ok): In a COPY or MOVE
    request, when the Request-URI is an address book collection, the
    URI targeted by the Destination HTTP Request header MUST identify
    a location where an address book collection can be created.
    (CARDDAV:max-resource-size): The resource submitted in the PUT
    request, or targeted by a COPY or MOVE request, MUST have a size
    in octets less than or equal to the value of the
    CARDDAV:max-resource-size property value (Section 6.2.3) on the
    address book collection where the resource will be stored.

6.3.2.2. Non-Standard vCard Properties and Parameters

 vCard provides a "standard mechanism for doing non-standard things".
 This extension support allows implementers to make use of non-
 standard vCard properties and parameters whose names are prefixed
 with the text "X-".
 Servers MUST support the use of non-standard properties and
 parameters in address object resources stored via the PUT method.
 Servers may need to enforce rules for their own "private" 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.  A server SHOULD ensure that any "private"

Daboo Standards Track [Page 17] RFC 6352 CardDAV August 2011

 properties or parameters it uses follow the convention of including a
 vendor ID in the "X-" name, as described in Section 3.8 of [RFC2426],
 e.g., "X-ABC-PRIVATE".

6.3.2.3. Address Object Resource Entity Tag

 The DAV:getetag property MUST be defined and set to a strong entity
 tag on all address object resources.
 A response to a GET request targeted at an address object resource
 MUST contain an ETag response header field indicating the current
 value of the strong entity tag of the address object resource.
 Servers SHOULD return a strong entity tag (ETag header) in a PUT
 response when the stored address object resource is equivalent by
 octet equality to the address 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 address object
 resource, have the DAV:getetag property returned, compare that value
 with the strong entity tag it received on the PUT response, and know
 that if they are equal, then the address 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 address
 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, a client may need to
 retrieve the modified address object resource (and ETag) as a basis
 for further changes, rather than use the address object resource it
 had sent with the PUT request.

7. Address Book Access Control

 CardDAV 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.

7.1. Additional Principal Properties

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

Daboo Standards Track [Page 18] RFC 6352 CardDAV August 2011

7.1.1. CARDDAV:addressbook-home-set Property

 Name:  addressbook-home-set
 Namespace:  urn:ietf:params:xml:ns:carddav
 Purpose:  Identifies the URL of any WebDAV collections that contain
    address book collections owned by the associated principal
    resource.
 Protected:  MAY be protected if the server has fixed locations in
    which address books are created.
 COPY/MOVE behavior:  This property value MUST be preserved in COPY
    and MOVE operations.
 allprop behavior:  SHOULD NOT be returned by a PROPFIND DAV:allprop
    request.
 Description:  The CARDDAV:addressbook-home-set property is meant to
    allow users to easily find the address book collections owned by
    the principal.  Typically, users will group all the address book
    collections that they own under a common collection.  This
    property specifies the URL of collections that are either address
    book collections or ordinary collections that have child or
    descendant address book collections owned by the principal.
 Definition:
     <!ELEMENT addressbook-home-set (DAV:href*)>
 Example:
     <C:addressbook-home-set xmlns:D="DAV:"
        xmlns:C="urn:ietf:params:xml:ns:carddav">
       <D:href>/bernard/addresses/</D:href>
     </C:addressbook-home-set>

7.1.2. CARDDAV:principal-address Property

 Name:  principal-address
 Namespace:  urn:ietf:params:xml:ns:carddav
 Purpose:  Identifies the URL of an address object resource that
    corresponds to the user represented by the principal.

Daboo Standards Track [Page 19] RFC 6352 CardDAV August 2011

 Protected:  MAY be protected if the server provides a fixed location
    for principal addresses.
 COPY/MOVE behavior:  This property value MUST be preserved in COPY
    and MOVE operations.
 allprop behavior:  SHOULD NOT be returned by a PROPFIND DAV:allprop
    request.
 Description:  The CARDDAV:principal-address property is meant to
    allow users to easily find contact information for users
    represented by principals on the system.  This property specifies
    the URL of the resource containing the corresponding contact
    information.  The resource could be an address object resource in
    an address book collection, or it could be a resource in a
    "regular" collection.
 Definition:
     <!ELEMENT principal-address (DAV:href)>
 Example:
     <C:principal-address xmlns:D="DAV:"
        xmlns:C="urn:ietf:params:xml:ns:carddav">
        <D:href>/system/cyrus.vcf</D:href>
     </C:principal-address>

8. Address Book Reports

 This section defines the reports that CardDAV servers MUST support on
 address book collections and address object resources.
 CardDAV servers MUST advertise support for these reports on all
 address book collections and address object resources with the
 DAV:supported-report-set property defined in Section 3.1.5 of
 [RFC3253].  CardDAV servers MAY also advertise support for these
 reports on ordinary collections.
 Some of these reports allow address data (from possibly multiple
 resources) to be returned.

8.1. REPORT Method

 The REPORT method (defined in Section 3.6 of [RFC3253]) provides an
 extensible mechanism for obtaining information about a resource.
 Unlike the PROPFIND method, which returns the value of one or more
 named properties, the REPORT method can involve more complex

Daboo Standards Track [Page 20] RFC 6352 CardDAV August 2011

 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.
 A server that supports this specification MUST support the
 DAV:expand-property report (defined in Section 3.8 of [RFC3253]).

8.2. Ordinary Collections

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

8.3. Searching Text: Collations

 Some of the reports defined in this section do text matches of
 character strings provided by the client and compared to stored
 address data.  Since vCard data is by default encoded in the UTF-8
 charset and may include characters outside of the US-ASCII charset
 range in some property and parameter values, there is a need to
 ensure that text matching follows well-defined rules.
 To deal with this, this specification makes use of the IANA Collation
 Registry defined in [RFC4790] to specify collations that may be used
 to carry out the text comparison operations with a well-defined rule.
 Collations supported by the server MUST support "equality" and
 "substring" match operations as per [RFC4790], Section 4.2, including
 the "prefix" and "suffix" options for "substring" matching.  CardDAV
 uses these match options for "equals", "contains", "starts-with", and
 "ends-with" match operations.
 CardDAV servers are REQUIRED to support the "i;ascii-casemap"
 [RFC4790] and "i;unicode-casemap" [RFC5051] collations and MAY
 support other collations.
 Servers MUST advertise the set of collations that they support via
 the CARDDAV:supported-collation-set property defined on any resource
 that supports reports that use collations.

Daboo Standards Track [Page 21] RFC 6352 CardDAV August 2011

 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;unicode-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 CARDDAV:supported-collation precondition
 error response.

8.3.1. CARDDAV:supported-collation-set Property

 Name:  supported-collation-set
 Namespace:  urn:ietf:params:xml:ns:carddav
 Purpose:  Identifies the set of collations supported by the server
    for text matching operations.
 Protected:  MUST be protected as it indicates support provided by the
    server.
 COPY/MOVE behavior:  This property value MUST be preserved in COPY
    and MOVE operations.
 allprop behavior:  SHOULD NOT be returned by a PROPFIND DAV:allprop
    request.
 Description:  The CARDDAV:supported-collation-set property contains
    two or more CARDDAV:supported-collation elements that specify the
    identifiers of the collations supported by the server.
 Definition:
       <!ELEMENT supported-collation-set (
             supported-collation
             supported-collation
             supported-collation*)>
       <!-- Both "i;ascii-casemap" and "i;unicode-casemap"
            will be present -->
       <!ELEMENT supported-collation (#PCDATA)>

Daboo Standards Track [Page 22] RFC 6352 CardDAV August 2011

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

8.4. Partial Retrieval

 Some address book reports defined in this document allow partial
 retrieval of address object resources.  A CardDAV client can specify
 what information to return in the body of an address book REPORT
 request.
 A CardDAV client can request particular WebDAV property values, all
 WebDAV property values, or a list of the names of the resource's
 WebDAV properties.  A CardDAV client can also request address data to
 be returned and whether all vCard properties should be returned or
 only particular ones.  See CARDDAV:address-data in Section 10.4.

8.5. Non-Standard Properties and Parameters

 Servers MUST support the use of non-standard vCard property or
 parameter names in the CARDDAV:address-data XML element in address
 book REPORT requests to allow clients to request that non-standard
 properties and parameters be returned in the address data provided in
 the response.
 Servers MAY support the use of non-standard vCard property or
 parameter names in the CARDDAV:prop-filter and CARDDAV:param-filter
 XML elements specified in the CARDDAV:filter XML element of address
 book REPORT requests.
 Servers MUST fail with the CARDDAV:supported-filter precondition if
 an address book REPORT request uses a CARDDAV:prop-filter or
 CARDDAV:param-filter XML element that makes reference to a non-
 standard vCard property or parameter name on which the server does
 not support queries.

8.6. CARDDAV:addressbook-query Report

 The CARDDAV:addressbook-query REPORT performs a search for all
 address object resources that match a specified filter.  The response
 of this report will contain all the WebDAV properties and address
 object resource data specified in the request.  In the case of the

Daboo Standards Track [Page 23] RFC 6352 CardDAV August 2011

 CARDDAV:address-data XML element, one can explicitly specify the
 vCard properties that should be returned in the address 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 CARDDAV:addressbook-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 WebDAV property results.  For
 instance, a request to retrieve the value of a WebDAV 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 CARDDAV:addressbook-query REPORT is REQUIRED.
 Marshalling:
    The request body MUST be a CARDDAV:addressbook-query XML element
    as defined in Section 10.3.
    The request MUST include a Depth header.  The scope of the query
    is determined by the value of the Depth header.  For example, to
    query all address object resources in an address book collection,
    the REPORT would use the address book collection as the Request-
    URI and specify a Depth of 1 or infinity.
    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 CARDDAV:addressbook-query
    REPORT request MUST contain a DAV:response element for each
    address object that matched the search filter.  Address data is
    returned in the CARDDAV:address-data XML element inside the
    DAV:propstat XML element.
 Preconditions:
    (CARDDAV:supported-address-data): The attributes "content-type"
    and "version" of the CARDDAV:address-data XML element (see
    Section 10.4) specify a media type supported by the server for
    address object resources.

Daboo Standards Track [Page 24] RFC 6352 CardDAV August 2011

    (CARDDAV:supported-filter): The CARDDAV:prop-filter (see
    Section 10.5.1) and CARDDAV:param-filter (see Section 10.5.2) XML
    elements used in the CARDDAV:filter XML element (see Section 10.5)
    in the REPORT request only make reference to vCard properties and
    parameters for which queries are supported by the server.  That
    is, if the CARDDAV:filter element attempts to reference an
    unsupported vCard property or parameter, this precondition is
    violated.  A server SHOULD report the CARDDAV:prop-filter or
    CARDDAV:param-filter for which it does not provide support.
        <!ELEMENT supported-filter (prop-filter*,
                                    param-filter*)>
    (CARDDAV:supported-collation): Any XML attribute specifying a
    collation MUST specify a collation supported by the server as
    described in Section 8.3.
 Postconditions:
    (DAV:number-of-matches-within-limits): The number of matching
    address 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.

8.6.1. Limiting Results

 A client can limit the number of results returned by the server
 through use of the CARDDAV:limit element in the request body.  This
 is useful when clients are only interested in a few matches or only
 have limited space to display results to users and thus don't need
 the overhead of receiving more than that.  When the results are
 truncated by the server, the server MUST follow the rules below for
 indicating a result set truncation to the client.

8.6.2. Truncation of Results

 A server MAY limit the number of resources in a response, for
 example, to limit the amount of work expended in processing a query,
 or as the result of an explicit limit set by the client.  If the
 result set is truncated because of such a limit, the response MUST
 use status code 207 (Multi-Status), return a DAV:multistatus response
 body, and indicate a status of 507 (Insufficient Storage) for the
 Request-URI.  That DAV:response element SHOULD include a DAV:error
 element with the DAV:number-of-matches-within-limits precondition, as
 defined in [RFC3744], Section 9.2.

Daboo Standards Track [Page 25] RFC 6352 CardDAV August 2011

 The server SHOULD also include the partial results in additional
 DAV:response elements.  If a client-requested limit is being applied,
 the 507 response for the Request-URI MUST NOT be included in
 calculating the limit (e.g., if the client requests that only a
 single result be returned, and multiple matches are present, then the
 DAV:multistatus response will include one DAV:response for the
 matching resource and one DAV:response for the 507 status on the
 Request-URI).

8.6.3. Example: Partial Retrieval of vCards Matching NICKNAME

 In this example, the client requests that the server search for
 address object resources that contain a NICKNAME property whose value
 equals some specific text and return specific vCard properties for
 those vCards found.  In addition, the DAV:getetag property is also
 requested and returned as part of the response.
 >> Request <<
 REPORT /home/bernard/addressbook/ HTTP/1.1
 Host: addressbook.example.com
 Depth: 1
 Content-Type: text/xml; charset="utf-8"
 Content-Length: xxxx
 <?xml version="1.0" encoding="utf-8" ?>
 <C:addressbook-query xmlns:D="DAV:"
                   xmlns:C="urn:ietf:params:xml:ns:carddav">
   <D:prop>
     <D:getetag/>
     <C:address-data>
       <C:prop name="VERSION"/>
       <C:prop name="UID"/>
       <C:prop name="NICKNAME"/>
       <C:prop name="EMAIL"/>
       <C:prop name="FN"/>
     </C:address-data>
   </D:prop>
   <C:filter>
     <C:prop-filter name="NICKNAME">
       <C:text-match collation="i;unicode-casemap"
                     match-type="equals"
       >me</C:text-match>
     </C:prop-filter>
   </C:filter>
 </C:addressbook-query>

Daboo Standards Track [Page 26] RFC 6352 CardDAV August 2011

 >> Response <<
 HTTP/1.1 207 Multi-Status
 Date: Sat, 11 Nov 2006 09:32:12 GMT
 Content-Type: text/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:carddav">
   <D:response>
     <D:href>/home/bernard/addressbook/v102.vcf</D:href>
     <D:propstat>
       <D:prop>
         <D:getetag>"23ba4d-ff11fb"</D:getetag>
         <C:address-data>BEGIN:VCARD
 VERSION:3.0
 NICKNAME:me
 UID:34222-232@example.com
 FN:Cyrus Daboo
 EMAIL:daboo@example.com
 END:VCARD
 </C:address-data>
       </D:prop>
       <D:status>HTTP/1.1 200 OK</D:status>
     </D:propstat>
   </D:response>
 </D:multistatus>

8.6.4. Example: Partial Retrieval of vCards Matching a Full Name or

      Email Address
 In this example, the client requests that the server search for
 address object resources that contain a FN property whose value
 contains some specific text or that contain an EMAIL property whose
 value contains other text and return specific vCard properties for
 those vCards found.  In addition, the DAV:getetag property is also
 requested and returned as part of the response.
 >> Request <<
 REPORT /home/bernard/addressbook/ HTTP/1.1
 Host: addressbook.example.com
 Depth: 1
 Content-Type: text/xml; charset="utf-8"
 Content-Length: xxxx

Daboo Standards Track [Page 27] RFC 6352 CardDAV August 2011

 <?xml version="1.0" encoding="utf-8" ?>
 <C:addressbook-query xmlns:D="DAV:"
                   xmlns:C="urn:ietf:params:xml:ns:carddav">
   <D:prop>
     <D:getetag/>
     <C:address-data>
       <C:prop name="VERSION"/>
       <C:prop name="UID"/>
       <C:prop name="NICKNAME"/>
       <C:prop name="EMAIL"/>
       <C:prop name="FN"/>
     </C:address-data>
   </D:prop>
   <C:filter test="anyof">
     <C:prop-filter name="FN">
       <C:text-match collation="i;unicode-casemap"
                     match-type="contains"
       >daboo</C:text-match>
     </C:prop-filter>
     <C:prop-filter name="EMAIL">
       <C:text-match collation="i;unicode-casemap"
                     match-type="contains"
       >daboo</C:text-match>
     </C:prop-filter>
   </C:filter>
 </C:addressbook-query>
 >> Response <<
 HTTP/1.1 207 Multi-Status
 Date: Sat, 11 Nov 2006 09:32:12 GMT
 Content-Type: text/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:carddav">
   <D:response>
     <D:href>/home/bernard/addressbook/v102.vcf</D:href>
     <D:propstat>
       <D:prop>
         <D:getetag>"23ba4d-ff11fb"</D:getetag>
         <C:address-data>BEGIN:VCARD
 VERSION:3.0
 NICKNAME:me
 UID:34222-232@example.com
 FN:David Boo
 EMAIL:daboo@example.com

Daboo Standards Track [Page 28] RFC 6352 CardDAV August 2011

 END:VCARD
 </C:address-data>
       </D:prop>
       <D:status>HTTP/1.1 200 OK</D:status>
     </D:propstat>
   </D:response>
   <D:response>
     <D:href>/home/bernard/addressbook/v104.vcf</D:href>
     <D:propstat>
       <D:prop>
         <D:getetag>"23ba4d-ff11fc"</D:getetag>
         <C:address-data>BEGIN:VCARD
 VERSION:3.0
 NICKNAME:oliver
 UID:34222-23222@example.com
 FN:Oliver Daboo
 EMAIL:oliver@example.com
 END:VCARD
 </C:address-data>
       </D:prop>
       <D:status>HTTP/1.1 200 OK</D:status>
     </D:propstat>
   </D:response>
 </D:multistatus>

8.6.5. Example: Truncated Results

 In this example, the client requests that the server search for
 address object resources that contain a FN property whose value
 contains some specific text and return the DAV:getetag property for
 two results only.  The server response includes a 507 status for the
 Request-URI indicating that there were more than two resources that
 matched the query, but that the server truncated the result set as
 requested by the client.
 >> Request <<
 REPORT /home/bernard/addressbook/ HTTP/1.1
 Host: addressbook.example.com
 Depth: 1
 Content-Type: text/xml; charset="utf-8"
 Content-Length: xxxx
 <?xml version="1.0" encoding="utf-8" ?>
 <C:addressbook-query xmlns:D="DAV:"
                   xmlns:C="urn:ietf:params:xml:ns:carddav">

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   <D:prop>
     <D:getetag/>
   </D:prop>
   <C:filter test="anyof">
     <C:prop-filter name="FN">
       <C:text-match collation="i;unicode-casemap"
                     match-type="contains"
       >daboo</C:text-match>
     </C:prop-filter>
   </C:filter>
   <C:limit>
     <C:nresults>2</C:nresults>
   </C:limit>
 </C:addressbook-query>
 >> Response <<
 HTTP/1.1 207 Multi-Status
 Date: Sat, 11 Nov 2006 09:32:12 GMT
 Content-Type: text/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:carddav">
   <D:response>
     <D:href>/home/bernard/addressbook/</D:href>
     <D:status>HTTP/1.1 507 Insufficient Storage</D:status>
     <D:error><D:number-of-matches-within-limits/></D:error>
     <D:responsedescription xml:lang="en">
       Only two matching records were returned
     </D:responsedescription>
   </D:response>
   <D:response>
     <D:href>/home/bernard/addressbook/v102.vcf</D:href>
     <D:propstat>
       <D:prop>
         <D:getetag>"23ba4d-ff11fb"</D:getetag>
       </D:prop>
       <D:status>HTTP/1.1 200 OK</D:status>
     </D:propstat>
   </D:response>
   <D:response>
     <D:href>/home/bernard/addressbook/v104.vcf</D:href>
     <D:propstat>
       <D:prop>
         <D:getetag>"23ba4d-ff11fc"</D:getetag>
       </D:prop>

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       <D:status>HTTP/1.1 200 OK</D:status>
     </D:propstat>
   </D:response>
 </D:multistatus>

8.7. CARDDAV:addressbook-multiget Report

 The CARDDAV:addressbook-multiget REPORT is used to retrieve specific
 address object resources from within a collection, if the Request-URI
 is a collection, or to retrieve a specific address object resource,
 if the Request-URI is an address object resource.  This report is
 similar to the CARDDAV:addressbook-query REPORT (see Section 8.6),
 except that it takes a list of DAV:href elements instead of a
 CARDDAV:filter element to determine which address object resources to
 return.
 Support for the addressbook-multiget REPORT is REQUIRED.
 Marshalling:
    The request body MUST be a CARDDAV:addressbook-multiget XML
    element (see Section 10.7), which MUST contain at least one
    DAV:href XML element and one optional CARDDAV:address-data element
    as defined in Section 10.4.  If DAV:href elements are present, the
    scope of the request is the set of resources identified by these
    elements, which all need to be members (not necessarily internal
    members) of the resource identified by the Request-URI.
    Otherwise, the scope is the resource identified by the Request-URI
    itself.
    The request MUST include a Depth: 0 header; however, the actual
    scope of the REPORT is determined as described above.
    The response body for a successful request MUST be a
    DAV:multistatus XML element.
    The response body for a successful CARDDAV:addressbook-multiget
    REPORT request MUST contain a DAV:response element for each
    address object resource referenced by the provided set of DAV:href
    elements.  Address data is returned in the CARDDAV:address-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.

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 Preconditions:
    (CARDDAV:supported-address-data): The attributes "content-type"
    and "version" of the CARDDAV:address-data XML elements (see
    Section 10.4) specify a media type supported by the server for
    address object resources.
 Postconditions:
    None.

8.7.1. Example: CARDDAV:addressbook-multiget Report

 In this example, the client requests the server to return specific
 vCard properties of the address 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://addressbook.example.com/home/bernard/addressbook/vcf1.vcf does
 not exist, resulting in an error status response.
 >> Request <<
 REPORT /home/bernard/addressbook/ HTTP/1.1
 Host: addressbook.example.com
 Depth: 1
 Content-Type: text/xml; charset="utf-8"
 Content-Length: xxxx
 <?xml version="1.0" encoding="utf-8" ?>
 <C:addressbook-multiget xmlns:D="DAV:"
                      xmlns:C="urn:ietf:params:xml:ns:carddav">
   <D:prop>
     <D:getetag/>
     <C:address-data>
       <C:prop name="VERSION"/>
       <C:prop name="UID"/>
       <C:prop name="NICKNAME"/>
       <C:prop name="EMAIL"/>
       <C:prop name="FN"/>
     </C:address-data>
   </D:prop>
   <D:href>/home/bernard/addressbook/vcf102.vcf</D:href>
   <D:href>/home/bernard/addressbook/vcf1.vcf</D:href>
 </C:addressbook-multiget>

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 >> Response <<
 HTTP/1.1 207 Multi-Status
 Date: Sat, 11 Nov 2006 09:32:12 GMT
 Content-Type: text/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:carddav">
   <D:response>
     <D:href>/home/bernard/addressbook/vcf102.vcf</D:href>
     <D:propstat>
       <D:prop>
         <D:getetag>"23ba4d-ff11fb"</D:getetag>
         <C:address-data>BEGIN:VCARD
 VERSION:3.0
 NICKNAME:me
 UID:34222-232@example.com
 FN:Cyrus Daboo
 EMAIL:daboo@example.com
 END:VCARD
 </C:address-data>
       </D:prop>
       <D:status>HTTP/1.1 200 OK</D:status>
     </D:propstat>
   </D:response>
   <D:response>
     <D:href>/home/bernard/addressbook/vcf1.vcf</D:href>
     <D:status>HTTP/1.1 404 Resource not found</D:status>
   </D:response>
 </D:multistatus>

8.7.2. Example: CARDDAV:addressbook-multiget Report

 In this example, the client requests the server to return vCard v4.0
 data of the address 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://addressbook.example.com/home/bernard/addressbook/vcf3.vcf
 exists but in a media type format that the server is unable to
 convert, resulting in an error status response.

Daboo Standards Track [Page 33] RFC 6352 CardDAV August 2011

 >> Request <<
 REPORT /home/bernard/addressbook/ HTTP/1.1
 Host: addressbook.example.com
 Depth: 1
 Content-Type: text/xml; charset="utf-8"
 Content-Length: xxxx
 <?xml version="1.0" encoding="utf-8" ?>
 <C:addressbook-multiget xmlns:D="DAV:"
                      xmlns:C="urn:ietf:params:xml:ns:carddav">
   <D:prop>
     <D:getetag/>
     <C:address-data content-type='text/vcard' version='4.0'/>
   </D:prop>
   <D:href>/home/bernard/addressbook/vcf3.vcf</D:href>
 </C:addressbook-multiget>
 >> Response <<
 HTTP/1.1 207 Multi-Status
 Date: Sat, 11 Nov 2006 09:32:12 GMT
 Content-Type: text/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:carddav">
   <D:response>
     <D:href>/home/bernard/addressbook/vcf3.vcf</D:href>
     <D:status>HTTP/1.1 415 Unsupported Media Type</D:status>
     <D:error><C:supported-address-data-conversion/></D:error>
     <D:responsedescription>Unable to convert from vCard v3.0
     to vCard v4.0</D:responsedescription>
   </D:response>
 </D:multistatus>

9. Client Guidelines

9.1. Restrict the Properties Returned

 Clients may not need all the properties in a vCard object when
 presenting information to the user, or looking up specific items for
 their email address, for example.  Since some property data can be
 large (e.g., PHOTO or SOUND with in-line content) clients can choose
 to ignore those by only requesting the specific items it knows it
 will use, through use of the CARDDAV:address-data XML element in the
 relevant reports.

Daboo Standards Track [Page 34] RFC 6352 CardDAV August 2011

 However, if a client needs to make a change to a vCard, it can only
 change the entire vCard data via a PUT request.  There is no way to
 incrementally make a change to a set of properties within a vCard
 object resource.  As a result, the client will have to cache the
 entire set of properties on a resource that is being changed.

9.2. Avoiding Lost Updates

 When resources are accessed by multiple clients, the possibility of
 clients overwriting each other's changes exists.  To alleviate this,
 clients SHOULD use the If-Match request header on PUT requests with
 the ETag of the previously retrieved resource data to check whether
 the resource was modified since it was previously retrieved.  If a
 precondition failure occurs, clients need to reload the resource and
 go through their own merge or conflict resolution process before
 writing back the data (again using the If-Match check).

9.3. Client Configuration

 When CardDAV clients need to be configured, the key piece of
 information that they require is the principal-URL of the user whose
 address book information is desired.  Servers SHOULD support the
 DAV:current-user-principal-URL property as defined in [RFC5397] to
 give clients a fast way to locate user principals.
 Given support for SRV records (Section 11) and DAV:current-user-
 principal-URL [RFC5397], users only need enter a user identifier,
 host name, and password to configure their client.  The client would
 take the host name and do an SRV lookup to locate the CardDAV server,
 then execute an authenticated PROPFIND on the root/resource looking
 for the DAV:current-user-principal-URL property.  The value returned
 gives the client direct access to the user's principal-URL and from
 there all the related CardDAV properties needed to locate address
 books.

9.4. Finding Other Users' Address Books

 For use cases of address book sharing, one might wish to find the
 address book belonging to another user.  To find other users' address
 books on the same server, the DAV:principal-property-search REPORT
 [RFC3744] can be used to search principals for matching properties
 and return specified properties for the matching principal resources.
 To search for an address book owned by a user named "Laurie", the
 REPORT request body would look like this:

Daboo Standards Track [Page 35] RFC 6352 CardDAV August 2011

 <?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:addressbook-home-set
        xmlns:C="urn:ietf:params:xml:ns:carddav"/>
     <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" all as matching DAV:displayname
 values, and the address books for each of these.

10. XML Element Definitions

10.1. CARDDAV:addressbook XML Element

 Name:  addressbook
 Namespace:  urn:ietf:params:xml:ns:carddav
 Purpose:  Specifies the resource type of an address book collection.
 Description:  See Section 5.2.
 Definition:
     <!ELEMENT addressbook EMPTY>

10.2. CARDDAV:supported-collation XML Element

 Name:  supported-collation
 Namespace:  urn:ietf:params:xml:ns:carddav
 Purpose:  Identifies a single collation via its collation identifier
    as defined by [RFC4790].
 Description:  The CARDDAV:supported-collation contains the text of a
    collation identifier as described in Section 8.3.1.

Daboo Standards Track [Page 36] RFC 6352 CardDAV August 2011

 Definition:
     <!ELEMENT supported-collation (#PCDATA)>
     <!-- PCDATA value: collation identifier -->

10.3. CARDDAV:addressbook-query XML Element

 Name:  addressbook-query
 Namespace:  urn:ietf:params:xml:ns:carddav
 Purpose:  Defines a report for querying address book data
 Description:  See Section 8.6.
 Definition:
     <!ELEMENT addressbook-query ((DAV:allprop |
                                   DAV:propname |
                                   DAV:prop)?, filter, limit?)>

10.4. CARDDAV:address-data XML Element

 Name:  address-data
 Namespace:  urn:ietf:params:xml:ns:carddav
 Purpose:  Specifies one of the following:
    1.  The parts of an address object resource that should be
        returned by a given address book REPORT request, and the media
        type and version for the returned data; or
    2.  The content of an address object resource in a response to an
        address book REPORT request.
 Description:  When used in an address book REPORT request, the
    CARDDAV:address-data XML element specifies which parts of address
    object resources need to be returned in the response.  If the
    CARDDAV:address-data XML element doesn't contain any CARDDAV:prop
    elements, address object resources will be returned in their
    entirety.  Additionally, a media type and version can be specified
    to request that the server return the data in that format if
    possible.
    Finally, when used in an address book REPORT response, the
    CARDDAV:address-data XML element specifies the content of an
    address object resource.  Given that XML parsers normalize the

Daboo Standards Track [Page 37] RFC 6352 CardDAV August 2011

    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 address object
    resources specified in the CARDDAV:address-data XML element.
    Furthermore, address object resources specified in the
    CARDDAV:address-data XML element MAY be invalid per their media
    type specification if the CARDDAV:address-data XML element part of
    the address book REPORT request did not specify required vCard
    properties (e.g., UID, etc.) or specified a CARDDAV:prop XML
    element with the "novalue" attribute set to "yes".
 Note:  The CARDDAV:address-data XML element is specified in requests
    and responses inside the DAV:prop XML element as if it were a
    WebDAV property.  However, the CARDDAV:address-data XML element is
    not a WebDAV property and as such it is not returned in PROPFIND
    responses nor used in PROPPATCH requests.
 Note:  The address data embedded within the CARDDAV:address-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 latter case, the
    vCard data cannot contain the character sequence "]]>", which is
    the end delimiter for the CDATA section.
 Definition:
     <!ELEMENT address-data (allprop | prop*)>
     when nested in the DAV:prop XML element in an address book
     REPORT request to specify which parts of address object
     resources should be returned in the response;
     <!ELEMENT address-data (#PCDATA)>
     <!-- PCDATA value: address data -->
     when nested in the DAV:prop XML element in an address book
     REPORT response to specify the content of a returned
     address object resource.
     <!ATTLIST address-data content-type CDATA "text/vcard"
                           version CDATA "3.0">
     <!-- content-type value: a MIME media type -->
     <!-- version value: a version string -->
     attributes can be used on each variant of the
     CALDAV:address-data XML element.

Daboo Standards Track [Page 38] RFC 6352 CardDAV August 2011

10.4.1. CARDDAV:allprop XML Element

 Name:  allprop
 Namespace:  urn:ietf:params:xml:ns:carddav
 Purpose:  Specifies that all vCard properties shall be returned.
 Description:  This element can be used when the client wants all
    vCard properties of components returned by a report.
 Definition:
     <!ELEMENT allprop EMPTY>
 Note: The CARDDAV:allprop element defined here has the same name as
 the DAV:allprop element defined in WebDAV.  However, the
 CARDDAV:allprop element defined here uses the
 "urn:ietf:params:xml:ns:carddav" namespace, as opposed to the "DAV:"
 namespace used for the DAV:allprop element defined in WebDAV.

10.4.2. CARDDAV:prop XML Element

 Name:  prop
 Namespace:  urn:ietf:params:xml:ns:carddav
 Purpose:  Defines which vCard properties to return in the response.
 Description:  The "name" attribute specifies the name of the vCard
    property to return (e.g., "NICKNAME").  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 vCard
    property name and any vCard parameters and a trailing ":" without
    the subsequent value data.
    vCard allows a "group" prefix to appear before a property name in
    the vCard data.  When the "name" attribute does not specify a
    group prefix, it MUST match properties in the vCard data without a
    group prefix or with any group prefix.  When the "name" attribute
    includes a group prefix, it MUST match properties that have
    exactly the same group prefix and name.  For example, a "name" set
    to "TEL" will match "TEL", "X-ABC.TEL", and "X-ABC-1.TEL" vCard
    properties.  A "name" set to "X-ABC.TEL" will match an "X-ABC.TEL"
    vCard property only; it will not match "TEL" or "X-ABC-1.TEL".

Daboo Standards Track [Page 39] RFC 6352 CardDAV August 2011

 Definition:
     <!ELEMENT prop EMPTY>
     <!ATTLIST prop name CDATA #REQUIRED
                novalue (yes | no) "no">
     <!-- name value: a vCard property name -->
     <!-- novalue value: "yes" or "no" -->
 Note: The CARDDAV:prop element defined here has the same name as the
 DAV:prop element defined in WebDAV.  However, the CARDDAV:prop
 element defined here uses the "urn:ietf:params:xml:ns:carddav"
 namespace, as opposed to the "DAV:" namespace used for the DAV:prop
 element defined in WebDAV.

10.5. CARDDAV:filter XML Element

 Name:  filter
 Namespace:  urn:ietf:params:xml:ns:carddav
 Purpose:  Determines which matching objects are returned.
 Description:  The "filter" element specifies the search filter used
    to match address objects that should be returned by a report.  The
    "test" attribute specifies whether any (logical OR) or all
    (logical AND) of the prop-filter tests need to match in order for
    the overall filter to match.
 Definition:
     <!ELEMENT filter (prop-filter*)>
     <!ATTLIST filter test (anyof | allof) "anyof">
     <!-- test value:
               anyof logical OR for prop-filter matches
               allof logical AND for prop-filter matches -->

10.5.1. CARDDAV:prop-filter XML Element

 Name:  prop-filter
 Namespace:  urn:ietf:params:xml:ns:carddav
 Purpose:  Limits the search to specific vCard properties.

Daboo Standards Track [Page 40] RFC 6352 CardDAV August 2011

 Description:  The CARDDAV:prop-filter XML element specifies search
    criteria on a specific vCard property (e.g., "NICKNAME").  An
    address object is said to match a CARDDAV:prop-filter if:
  • A vCard property of the type specified by the "name" attribute

exists, and the CARDDAV:prop-filter is empty, or it matches any

       specified CARDDAV:text-match or CARDDAV:param-filter
       conditions.  The "test" attribute specifies whether any
       (logical OR) or all (logical AND) of the text-filter and param-
       filter tests need to match in order for the overall filter to
       match.
    or:
  • A vCard property of the type specified by the "name" attribute

does not exist, and the CARDDAV:is-not-defined element is

       specified.
    vCard allows a "group" prefix to appear before a property name in
    the vCard data.  When the "name" attribute does not specify a
    group prefix, it MUST match properties in the vCard data without a
    group prefix or with any group prefix.  When the "name" attribute
    includes a group prefix, it MUST match properties that have
    exactly the same group prefix and name.  For example, a "name" set
    to "TEL" will match "TEL", "X-ABC.TEL", "X-ABC-1.TEL" vCard
    properties.  A "name" set to "X-ABC.TEL" will match an "X-ABC.TEL"
    vCard property only, it will not match "TEL" or "X-ABC-1.TEL".
 Definition:
     <!ELEMENT prop-filter (is-not-defined |
                            (text-match*, param-filter*))>
     <!ATTLIST prop-filter name CDATA #REQUIRED
                           test (anyof | allof) "anyof">
     <!-- name value: a vCard property name (e.g., "NICKNAME")
       test value:
           anyof logical OR for text-match/param-filter matches
           allof logical AND for text-match/param-filter matches -->

10.5.2. CARDDAV:param-filter XML Element

 Name:  param-filter
 Namespace:  urn:ietf:params:xml:ns:carddav
 Purpose:  Limits the search to specific parameter values.

Daboo Standards Track [Page 41] RFC 6352 CardDAV August 2011

 Description:  The CARDDAV:param-filter XML element specifies search
    criteria on a specific vCard property parameter (e.g., TYPE) in
    the scope of a given CARDDAV:prop-filter.  A vCard property is
    said to match a CARDDAV:param-filter if:
  • A parameter of the type specified by the "name" attribute

exists, and the CARDDAV:param-filter is empty, or it matches

       the CARDDAV:text-match conditions if specified.
    or:
  • A parameter of the type specified by the "name" attribute does

not exist, and the CARDDAV:is-not-defined element is specified.

 Definition:
     <!ELEMENT param-filter (is-not-defined | text-match)?>
     <!ATTLIST param-filter name CDATA #REQUIRED>
     <!-- name value: a property parameter name (e.g., "TYPE") -->

10.5.3. CARDDAV:is-not-defined XML Element

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

10.5.4. CARDDAV:text-match XML Element

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

Daboo Standards Track [Page 42] RFC 6352 CardDAV August 2011

 Description:  The CARDDAV:text-match XML element specifies text used
    for a substring match against the vCard property or parameter
    value specified in an address book 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;unicode-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 CATEGORIES property not set to
    PERSON.
    The "match-type" attribute is used to indicate the type of match
    operation to use.  Possible choices are:
       "equals" - an exact match to the target string
       "contains" - a substring match, matching anywhere within the
       target string
       "starts-with" - a substring match, matching only at the start
       of the target string
       "ends-with" - a substring match, matching only at the end of
       the target string
 Definition:
     <!ELEMENT text-match (#PCDATA)>
     <!-- PCDATA value: string -->
     <!ATTLIST text-match
        collation        CDATA "i;unicode-casemap"
        negate-condition (yes | no) "no"
        match-type (equals|contains|starts-with|ends-with) "contains">

10.6. CARDDAV:limit XML Element

 Name:  limit
 Namespace:  urn:ietf:params:xml:ns:carddav
 Purpose:  Specifies different types of limits that can be applied to
    the results returned by the server.

Daboo Standards Track [Page 43] RFC 6352 CardDAV August 2011

 Description:  The CARDDAV:limit XML element can be used to specify
    different types of limits that the client can request the server
    to apply to the results returned by the server.  Currently, only
    the CARDDAV:nresults limit can be used; other types of limit could
    be defined in the future.
 Definition:
     <!ELEMENT limit (nresults)>

10.6.1. CARDDAV:nresults XML Element

 Name:  nresults
 Namespace:  urn:ietf:params:xml:ns:carddav
 Purpose:  Specifies a limit on the number of results returned by the
    server.
 Description:  The CARDDAV:nresults XML element contains a requested
    maximum number of DAV:response elements to be returned in the
    response body of a query.  The server MAY disregard this limit.
    The value of this element is an unsigned integer.
 Definition:
     <!ELEMENT nresults (#PCDATA)>
     <!-- nresults value: unsigned integer, must be digits -->

10.7. CARDDAV:addressbook-multiget XML Element

 Name:  addressbook-multiget
 Namespace:  urn:ietf:params:xml:ns:carddav
 Purpose:  CardDAV report used to retrieve specific address objects
    via their URIs.
 Description:  See Section 8.7.
 Definition:
     <!ELEMENT addressbook-multiget ((DAV:allprop |
                                      DAV:propname |
                                      DAV:prop)?,
                                      DAV:href+)>

Daboo Standards Track [Page 44] RFC 6352 CardDAV August 2011

11. Service Discovery via SRV Records

 [RFC2782] defines a DNS-based service discovery protocol that has
 been widely adopted as a means of locating particular services within
 a local area network and beyond, using SRV RRs.
 This specification adds two service types for use with SRV records:
 carddav:  Identifies a CardDAV server that uses HTTP without TLS
    [RFC2818].
 carddavs:  Identifies a CardDAV server that uses HTTP with TLS
    [RFC2818].
 Example: non-TLS service record
     _carddav._tcp     SRV 0 1 80 addressbook.example.com.
 Example: TLS service
     _carddavs._tcp    SRV 0 1 443 addressbook.example.com.

12. Internationalization Considerations

 CardDAV allows internationalized strings to be stored and retrieved
 for the description of address book collections (see Section 6.2.1).
 The CARDDAV:addressbook-query REPORT (Section 8.6) includes a text
 searching option controlled by the CARDDAV:text-match element and
 details of character handling are covered in the description of that
 element (see Section 10.5.4).

13. 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,
 if HTTP Basic authentication [RFC2617] is available, the server MUST
 allow TLS to be used at the same time, and it SHOULD prevent use of
 Basic authentication when TLS is not in use.  Clients SHOULD use TLS
 whenever possible.
 With the ACL extension [RFC3744] present, WebDAV allows control over
 who can access (read or write) any resource on the WebDAV server.  In
 addition, WebDAV ACL provides for an "inheritance" mechanism, whereby
 resources may inherit access privileges from other resources.  Often,
 the "other" resource is a parent collection of the resource itself.
 Servers are able to support address books that are "private"

Daboo Standards Track [Page 45] RFC 6352 CardDAV August 2011

 (accessible only to the "owner"), "shared" (accessible to the owner
 and other specified authenticated users), and "public" (accessible to
 any authenticated or unauthenticated users).  When provisioning
 address books of a particular type, servers MUST ensure that the
 correct privileges are applied on creation.  In particular, private
 and shared address books MUST NOT be accessible by unauthenticated
 users (to prevent data from being automatically searched or indexed
 by web "crawlers").
 Clients SHOULD warn users in an appropriate fashion when they copy or
 move address data from a private address book to a shared address
 book or public address book.  Clients SHOULD provide a clear
 indication as to which address books are private, shared, or public.
 Clients SHOULD provide an appropriate warning when changing access
 privileges for a private or shared address book with data so as to
 allow unauthenticated users access.
 This specification currently relies on standard HTTP authentication
 mechanisms for identifying users.  These comprise Basic and Digest
 authentication [RFC2617] as well as TLS [RFC2818] using client-side
 certificates.

14. IANA Consideration

 This document uses a URN to describe a new XML namespace conforming
 to the registry mechanism described in [RFC3688].

14.1. Namespace Registration

 Registration request for the carddav namespace:
 URI: urn:ietf:params:xml:ns:carddav
 Registrant Contact: The IESG <iesg@ietf.org>
 XML: None - not applicable for namespace registrations.

15. Acknowledgments

 Thanks go to Lisa Dusseault and Bernard Desruisseaux for their work
 on CalDAV, on which CardDAV is heavily based.  The following
 individuals contributed their ideas and support for writing this
 specification: Mike Douglass, Stefan Eissing, Helge Hess, Arnaud
 Quillaud, Julian Reschke, Elias Sinderson, Greg Stein, Wilfredo
 Sanchez, and Simon Vaillancourt.

Daboo Standards Track [Page 46] RFC 6352 CardDAV August 2011

16. References

16.1. Normative References

 [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
            Requirement Levels", BCP 14, RFC 2119, March 1997.
 [RFC2426]  Dawson, F. and T. Howes, "vCard MIME Directory Profile",
            RFC 2426, September 1998.
 [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.
 [RFC2617]  Franks, J., Hallam-Baker, P., Hostetler, J., Lawrence, S.,
            Leach, P., Luotonen, A., and L. Stewart, "HTTP
            Authentication: Basic and Digest Access Authentication",
            RFC 2617, June 1999.
 [RFC2782]  Gulbrandsen, A., Vixie, P., and L. Esibov, "A DNS RR for
            specifying the location of services (DNS SRV)", RFC 2782,
            February 2000.
 [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.
 [RFC3744]  Clemm, G., Reschke, J., Sedlar, E., and J. Whitehead, "Web
            Distributed Authoring and Versioning (WebDAV)
            Access Control Protocol", RFC 3744, May 2004.
 [RFC4790]  Newman, C., Duerst, M., and A. Gulbrandsen, "Internet
            Application Protocol Collation Registry", RFC 4790,
            March 2007.
 [RFC4918]  Dusseault, L., "HTTP Extensions for Web Distributed
            Authoring and Versioning (WebDAV)", RFC 4918, June 2007.
 [RFC5051]  Crispin, M., "i;unicode-casemap - Simple Unicode Collation
            Algorithm", RFC 5051, October 2007.

Daboo Standards Track [Page 47] RFC 6352 CardDAV August 2011

 [RFC5246]  Dierks, T. and E. Rescorla, "The Transport Layer Security
            (TLS) Protocol Version 1.2", RFC 5246, August 2008.
 [RFC5280]  Cooper, D., Santesson, S., Farrell, S., Boeyen, S.,
            Housley, R., and W. Polk, "Internet X.509 Public Key
            Infrastructure Certificate and Certificate Revocation List
            (CRL) Profile", RFC 5280, May 2008.
 [RFC5397]  Sanchez, W. and C. Daboo, "WebDAV Current Principal
            Extension", RFC 5397, December 2008.
 [RFC5689]  Daboo, C., "Extended MKCOL for Web Distributed Authoring
            and Versioning (WebDAV)", RFC 5689, September 2009.
 [RFC6350]  Perreault, S., "vCard Format Specification", RFC 6350,
            August 2011.
 [W3C.REC-xml-20081126]
            Bray, T., Paoli, J., Sperberg-McQueen, C., Maler, E., and
            F. Yergeau, "Extensible Markup Language (XML) 1.0 (Fifth
            Edition)", World Wide Web Consortium Recommendation REC-
            xml-20081126, November 2008,
            <http://www.w3.org/TR/2008/REC-xml-20081126>.

16.2. Informative References

 [IMSP]     Myers, J., "IMSP - Internet Message Support Protocol",
            Work in Progress, June 1995.
 [RFC2244]  Newman, C. and J. Myers, "ACAP -- Application
            Configuration Access Protocol", RFC 2244, November 1997.
 [RFC4510]  Zeilenga, K., "Lightweight Directory Access Protocol
            (LDAP): Technical Specification Road Map", RFC 4510,
            June 2006.

Author's Address

 Cyrus Daboo
 Apple, Inc.
 1 Infinite Loop
 Cupertino, CA  95014
 USA
 EMail: cyrus@daboo.name
 URI:   http://www.apple.com/

Daboo Standards Track [Page 48]

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