SIMPLE J. Rosenberg
Internet-Draft dynamicsoft
Expires: April 26, 2004 October 27, 2003
An Extensible Markup Language (XML) Configuration Access Protocol
(XCAP) Usage for Resource Lists
draft-ietf-simple-xcap-list-usage-01
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Copyright Notice
Copyright (C) The Internet Society (2003). All Rights Reserved.
Abstract
This document describes a usage of the Extensible Markup Language
(XML) Configuration Access Protocol (XCAP) for manipulating lists of
resources. These lists can be used as presence lists (also known as
buddy lists or rosters), but this specification does not restrict
their usage to that.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . 4
3. Application Unique ID . . . . . . . . . . . . . . . . . . . 5
4. Structure of a Resource List . . . . . . . . . . . . . . . . 6
5. Resource Interdependencies . . . . . . . . . . . . . . . . . 8
6. Additional Constraints . . . . . . . . . . . . . . . . . . . 9
7. Naming Conventions . . . . . . . . . . . . . . . . . . . . . 10
8. Authorization Policies . . . . . . . . . . . . . . . . . . . 11
9. XML Schema . . . . . . . . . . . . . . . . . . . . . . . . . 12
10. Example Document . . . . . . . . . . . . . . . . . . . . . . 14
11. Security Considerations . . . . . . . . . . . . . . . . . . 15
12. IANA Considerations . . . . . . . . . . . . . . . . . . . . 16
12.1 XCAP Application Usage ID . . . . . . . . . . . . . . . . . 16
12.2 application/resource-lists+xml MIME Type . . . . . . . . . . 16
12.3 URN Sub-Namespace Registration for
urn:ietf:params:xml:ns:resource-lists . . . . . . . . . . . 17
Normative References . . . . . . . . . . . . . . . . . . . . 18
Informative References . . . . . . . . . . . . . . . . . . . 19
Author's Address . . . . . . . . . . . . . . . . . . . . . . 19
Intellectual Property and Copyright Statements . . . . . . . 20
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1. Introduction
In many communications applications, it is neccesary for the network
to have access to a list of resources that represent a group that the
user would like to apply an action to. One such example is a presence
list [13]. These lists are used by Session Initiation Protocol (SIP)
for Instant Messaging and Presence (SIMPLE) [9]Resource List Servers
(RLS) [11] for processing list subscriptions. Another example might
be list of recipients for an instant message, or a list of users to
invite to a conference bridge.
Generally, these lists will need to be manipulated by the end users
of the system, and used by servers in the network. To support such
manipulations, the XML Configuration Access Protocol (XCAP) [7] has
been defined. XCAP requires application usages to standardize several
pieces of information, including an application unique ID (AUID), an
XML schema, and various other pieces of information. This
specification fulfills those requirements.
The XML schema defined here has several other usages outside of XCAP:
1. A PC client application will need to know the users in the
presence list, so that it can generate a subscription to each
one. This information represents user provisioned data for the
application. Typically, this information is stored on local disk
in a proprietary file format. By defining a standard format, the
same list can be used by a multiplicity of different client
applications, providing portability across them.
2. It is common for users to share presence lists. As an example,
user A may have three people in their list that they wish to tell
user B about. User A would like to send an email to user B with
an attachment describing these three people. Should user B open
the attachment, the three people can be added to their own
presence list. Doing this requires a standardized format for
exchanging lists over email, instant messaging, and other
communications protocols.
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2. Terminology
In this document, the key words "MUST", "MUST NOT", "REQUIRED",
"SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY",
and "OPTIONAL" are to be interpreted as described in RFC 2119 [1] and
indicate requirement levels for compliant implementations.
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3. Application Unique ID
XCAP requires application usages to define a unique application usage
ID (AUID) in either the IETF tree or a vendor tree. This
specification defines the "resource-lists" AUID within the IETF tree,
via the IANA registration in Section 12.
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4. Structure of a Resource List
A resource list is an XML [2] document that MUST be well-formed and
SHOULD be valid. Resource list documents MUST be based on XML 1.0 and
MUST be encoded using UTF-8. This specification makes use of XML
namespaces for identifying resource list documents and document
fragments. The namespace URI for elements defined by this
specification is a URN [3], using the namespace identifier 'ietf'
defined by [5] and extended by [6]. This URN is:
urn:ietf:params:xml:ns:resource-lists
A resource list document begins with the root element tag
``resource-lists''. It consists of any number of ``list''
sub-elements, each of which is a resource list. Other elements from
different namespaces MAY be present for the purposes of
extensibility; elements or attributes from unknown namespaces MUST be
ignored. There are three attributes associated with this element. The
first, "name", MUST be present:
name: This attribute is a descriptive name for the list. It MUST
be unique amongst all other list elements within the same parent
element.
Each list element will also have boolean attributes which indicate a
specific action that may be made against that list. This
specification defines a single attribute - subscribeable - which
indicates that the list may be subscribed to using the SIP event list
specification [11]. Extensions to this application usage MAY define
additional boolean elements, each within a different namespace, for
the purposes of indicating other actions that may be peformed. When
an attribute is absent, it implies that the operation is not
supported.
The third other attribute, "uri" MAY be present. It provides a URI
that can be used to access the list, for example, using the SIP event
notification extension for lists [11]. As a result, the URI MUST be
either a SIP URI or a pres URI [12].
Each list element is composed of a sequence of entry elements, list
elements, external elements. The ability of a list element to contain
other list elements means that a resource list can be hierarchically
structured. An entry element describes a single presentity that is
part of the list. An external element contains a reference to a list
stored on another server. A list element can also contain elements
from other namespaces, for the purposes of extensibility.
The entry element describes a single resource. The entry element has
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two attributes:
name: This mandatory attribute is a unique identifier amongst all
other entry elements of the same parent.
uri: This optional attribute is a URI that is used to access the
resource. It MUST be either a SIP or pres URI.
The entry element contains a sequence of other elements. Only one
such element is defined at this time, which is the display-name. This
element provides a UTF-8 encoded string, meant for consumption by the
user, that describes the resource. Unlike the "name" attribute of the
entry element, the display-name has no uniqueness requirements. Other
elements from other namespaces MAY be included. This is meant to
support the inclusion of other information about the entry, such as a
phone number or postal address.
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5. Resource Interdependencies
An XCAP server supporting this application usage need only worry
about a single data interdependency - the "uri" attribute of the list
element.
If the "uri" attribute is absent in a document written to an XCAP
server, but the "subscribeable" flag is true, the XCAP server MUST
allocate a URI for this list. This allocated URI MUST be globally
unique, and MUST route to an RLS which will handle list subscriptions
for the list defined by the document. The server MUST set the uri
attribute of the document with this URI.
A server MUST NOT delete the "uri" attribute, however, should a
client change the subscribeable flag to false after the server has
allocated a URI.
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6. Additional Constraints
There are no constraints on the document beyond those described in
the schema.
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7. Naming Conventions
There are no naming conventions that need to be defined for this
application usage. A subscription to a resource list will be to a
specific URI. That URI will be one of the "uri" attributes defined in
a list within one of the documents managed by an XCAP server.
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8. Authorization Policies
This application usage does not modify the default XCAP authorization
policy, which is that only a user can read, write or modify their own
documents. A server can allow priveleged users to modify documents
that they don't own, but the establishment and indication of such
policies is outside the scope of this document. It is anticipated
that a future application usage will define which users are allowed
to modify a list resource.
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9. XML Schema
The following is the XML schema definition of the resource list:
<?xml version="1.0" encoding="UTF-8"?>
<xs:schema targetNamespace="urn:ietf:params:xml:ns:resource-lists"
xmlns:xs="http://www.w3.org/2001/XMLSchema"
xmlns="urn:ietf:params:xml:ns:resource-lists"
elementFormDefault="qualified" attributeFormDefault="unqualified">
<xs:element name="resource-lists">
<xs:complexType>
<xs:sequence>
<xs:element name="list" type="listType" minOccurs="0"
maxOccurs="unbounded"/>
</xs:sequence>
</xs:complexType>
</xs:element>
<xs:complexType name="listType">
<xs:sequence maxOccurs="unbounded">
<xs:choice>
<xs:element name="list" minOccurs="0" maxOccurs="unbounded">
<xs:complexType>
<xs:complexContent>
<xs:extension base="listType"/>
</xs:complexContent>
</xs:complexType>
</xs:element>
<xs:element name="external" type="xs:anyURI" minOccurs="0"
maxOccurs="unbounded"/>
<xs:element name="entry" type="entryType" minOccurs="0"
maxOccurs="unbounded"/>
<xs:any namespace="##other" processContents="lax"
minOccurs="0" maxOccurs="unbounded"/>
</xs:choice>
</xs:sequence>
<xs:attribute name="name" type="xs:string" use="required"/>
<xs:attribute name="uri" type="xs:anyURI" use="optional"/>
<xs:attribute name="subscribeable" type="xs:boolean" use="optional"/>
<xs:anyAttribute namespace="##other"/>
</xs:complexType>
<xs:complexType name="entryType">
<xs:sequence>
<xs:element name="display-name" type="display-nameType"/>
<xs:any namespace="##other" processContents="lax"
minOccurs="0" maxOccurs="unbounded"/>
</xs:sequence>
<xs:attribute name="name" type="xs:string" use="required"/>
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<xs:attribute name="uri" type="xs:anyURI" use="optional"/>
</xs:complexType>
<xs:simpleType name="display-nameType">
<xs:restriction base="xs:string"/>
</xs:simpleType>
</xs:schema>
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10. Example Document
The following is an example of a document compliant to the schema:
<?xml version="1.0" encoding="UTF-8"?>
<resource-lists xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
<list name="friends" uri="sip:friends@example.com" subscribeable="true">
<entry name="Bill" uri="sip:bill@example.com">
<display-name>Bill Doe</display-name>
</entry>
<list name="close-friends" uri="sip:close-friends@example.com"
subscribeable="true">
<entry name="Joe" uri="sip:joe@example.com">
<display-name>Joe Smith</display-name>
</entry>
<entry name="Nancy" uri="sip:nancy@example.com">
<display-name>Nancy Gross</display-name>
</entry>
<external>http://www.example.org/xcap/resource-lists/users/a/foo
</external>
</list>
</list>
</resource-lists>
TODO: formally validate against schema.
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11. Security Considerations
The configuration information defined by this application usage is
particularly sensitive. It represents the principle set of people
with whom a user would like to communicate. As a result, clients
SHOULD use TLS when contacting servers in order to fetch this
information. Note that this does not represent a change in
requirement strength from XCAP.
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12. IANA Considerations
There are several IANA considerations associated with this
specification.
12.1 XCAP Application Usage ID
This section registers a new XCAP Application Usage ID (AUID)
according to the IANA procedures defined in [7].
Name of the AUID: resource-lists
Description: A resource list application is any application that
needs access to a list of resources, identified by a URI, to which
operations, such as subscriptions, can be applied.
12.2 application/resource-lists+xml MIME Type
MIME media type name: application
MIME subtype name: resource-lists+xml
Mandatory parameters: none
Optional parameters: Same as charset parameter application/xml as
specified in RFC 3023 [4].
Encoding considerations: Same as encoding considerations of
application/xml as specified in RFC 3023 [4].
Security considerations: See Section 10 of RFC 3023 [4] and
Section 11 of this specification.
Interoperability considerations: none.
Published specification: This document.
Applications which use this media type: This document type has
been used to support subscriptions to lists of users [11] for
SIP-based presence [9].
Additional Information:
Magic Number: None
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File Extension: .rl or .xml
Macintosh file type code: "TEXT"
Personal and email address for further information: Jonathan
Rosenberg, jdrosen@jdrosen.net
Intended usage: COMMON
Author/Change controller: The IETF.
12.3 URN Sub-Namespace Registration for
urn:ietf:params:xml:ns:resource-lists
This section registers a new XML namespace, as per the guidelines in
[6]
URI: The URI for this namespace is
urn:ietf:params:xml:ns:resource-lists.
Registrant Contact: IETF, SIMPLE working group, (simple@ietf.org),
Jonathan Rosenberg (jdrosen@jdrosen.net).
XML:
BEGIN
<?xml version="1.0"?>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML Basic 1.0//EN"
"http://www.w3.org/TR/xhtml-basic/xhtml-basic10.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<meta http-equiv="content-type"
content="text/html;charset=iso-8859-1"/>
<title>Resource Lists Namespace</title>
</head>
<body>
<h1>Namespace for Resource Lists</h1>
<h2>application/resource-lists+xml</h2>
<p>See <a href="[[[URL of published RFC]]]">RFCXXXX</a>.</p>
</body>
</html>
END
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Normative References
[1] Bradner, S., "Key words for use in RFCs to Indicate Requirement
Levels", BCP 14, RFC 2119, March 1997.
[2] Bray, T., Paoli, J., Sperberg-McQueen, C. and E. Maler,
"Extensible Markup Language (XML) 1.0 (Second Edition)", W3C REC
REC-xml-20001006, October 2000.
[3] Moats, R., "URN Syntax", RFC 2141, May 1997.
[4] Murata, M., St. Laurent, S. and D. Kohn, "XML Media Types", RFC
3023, January 2001.
[5] Moats, R., "A URN Namespace for IETF Documents", RFC 2648,
August 1999.
[6] Mealling, M., "The IETF XML Registry",
draft-mealling-iana-xmlns-registry-05 (work in progress), June
2003.
[7] Rosenberg, J., "The Extensible Markup Language (XML)
Configuration Access Protocol (XCAP)",
draft-ietf-simple-xcap-00 (work in progress), June 2003.
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Informative References
[8] Day, M., Rosenberg, J. and H. Sugano, "A Model for Presence and
Instant Messaging", RFC 2778, February 2000.
[9] Rosenberg, J., "A Presence Event Package for the Session
Initiation Protocol (SIP)", draft-ietf-simple-presence-10 (work
in progress), January 2003.
[10] Roach, A., "Session Initiation Protocol (SIP)-Specific Event
Notification", RFC 3265, June 2002.
[11] Roach, A., Rosenberg, J. and B. Campbell, "A Session Initiation
Protocol (SIP) Event Notification Extension for Resource
Lists", draft-ietf-simple-event-list-04 (work in progress),
June 2003.
[12] Peterson, J., "Common Profile for Presence (CPP)",
draft-ietf-impp-pres-04 (work in progress), October 2003.
[13] Rosenberg, J. and M. Isomaki, "Requirements for Manipulation of
Data Elements in Session Initiation Protocol (SIP) for Instant
Messaging and Presence Leveraging Extensions (SIMPLE) Systems",
draft-ietf-simple-data-req-03 (work in progress), June 2003.
Author's Address
Jonathan Rosenberg
dynamicsoft
600 Lanidex Plaza
Parsippany, NJ 07052
US
Phone: +1 973 952-5000
EMail: jdrosen@dynamicsoft.com
URI: http://www.jdrosen.net
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