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.

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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

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.

   6.1.1.  Example: Using OPTIONS for the Discovery of

     6.3.2.1.  Additional Preconditions for PUT, COPY, and

     6.3.2.2.  Non-Standard vCard Properties and Parameters . . . 17

   8.6.3.  Example: Partial Retrieval of vCards Matching

   8.6.4.  Example: Partial Retrieval of vCards Matching a

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

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.

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.

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.

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.

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.

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.

Address Book Resources

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

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.

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.

Additional Precondition for GET

This specification creates additional preconditions for the GET method.

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.

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.

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

Address Book Feature

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.

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.

Address Book Properties

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.

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)>

Example:

   <C:addressbook-description xml:lang="fr-CA"
      xmlns:C="urn:ietf:params:xml:ns:carddav"
   >Adresses de Oliver Daboo</C:addressbook-description>

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

  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">

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>

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.

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)>

Example:

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

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.

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.

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.

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>

>> 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>

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.

>> 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:[email protected] 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.

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.

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.

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"

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".

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.

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.

Additional Principal Properties

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

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>

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.

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>

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.

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

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).

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.

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.

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.

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*)>

     <!ELEMENT supported-collation (#PCDATA)>

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>

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.

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.

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

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.

  (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.

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.

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.

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).

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>

>> 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:[email protected] FN:Cyrus Daboo EMAIL:[email protected] END:VCARD </C:address-data>

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

</D:multistatus>

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

<?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:[email protected] FN:David Boo EMAIL:[email protected]

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:[email protected] FN:Oliver Daboo EMAIL:[email protected] END:VCARD </C:address-data>

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

</D:multistatus>

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">

 <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>

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

</D:multistatus>

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.

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.

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>

>> 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:[email protected] FN:Cyrus Daboo EMAIL:[email protected] 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>

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.

>> 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>

Client Guidelines

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.

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.

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).

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.

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:

<?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.

Definition:

   <!ELEMENT supported-collation (#PCDATA)>

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

  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 <, >, & 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)>

   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">

   attributes can be used on each variant of the
   CALDAV:address-data XML element.

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".

Definition:

   <!ELEMENT prop EMPTY>

   <!ATTLIST prop name CDATA #REQUIRED
              novalue (yes | no) "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">

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.

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">

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.

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>

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.

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)>

   <!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.

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)>

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+)>

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"

(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 <[email protected]>

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.

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.

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: [email protected] URI: http://www.apple.com/