SIMPLE J. Rosenberg
Internet-Draft dynamicsoft
Expires: August 15, 2004 February 15, 2004
An Extensible Markup Language (XML) Format for Representing Resource
Lists
draft-ietf-simple-xcap-list-usage-02
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Copyright Notice
Copyright (C) The Internet Society (2004). All Rights Reserved.
Abstract
In multimedia communications, presence and instant messaging systems,
there is a need to represent lists of Uniform Resource Identifiers
(URIs). These lists, which typically reside on a server, can be
subscribed to, in order to learn the presence status of a group of
users. A Session Initiation Protocol (SIP) INVITE message can be sent
to them, causing the creation of a conference call. This
specification defines an Extensible Markup Language (XML) document
format for representing resource lists. Such a document can be
manipulated by clients using the XML Configuration Access Protocol
(XCAP), although other techniques are permitted.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 4
3. Structure of a Resource List . . . . . . . . . . . . . . . . . 5
4. XML Schema . . . . . . . . . . . . . . . . . . . . . . . . . . 7
5. Example Document . . . . . . . . . . . . . . . . . . . . . . . 9
6. Usage with XCAP . . . . . . . . . . . . . . . . . . . . . . . 10
6.1 Application Unique ID . . . . . . . . . . . . . . . . . . . . 10
6.2 MIME Type . . . . . . . . . . . . . . . . . . . . . . . . . . 10
6.3 XML Schema . . . . . . . . . . . . . . . . . . . . . . . . . . 10
6.4 Additional Constraints . . . . . . . . . . . . . . . . . . . . 10
6.5 Data Semantics . . . . . . . . . . . . . . . . . . . . . . . . 10
6.6 Naming Conventions . . . . . . . . . . . . . . . . . . . . . . 10
6.7 Resource Interdependencies . . . . . . . . . . . . . . . . . . 10
6.8 Authorization Policies . . . . . . . . . . . . . . . . . . . . 11
7. Security Considerations . . . . . . . . . . . . . . . . . . . 12
8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 13
8.1 XCAP Application Usage ID . . . . . . . . . . . . . . . . . . 13
8.2 application/resource-lists+xml MIME Type . . . . . . . . . . . 13
8.3 URN Sub-Namespace Registration for
urn:ietf:params:xml:ns:resource-lists . . . . . . . . . . . . 14
8.4 Resource List Schema Registration . . . . . . . . . . . . . . 15
Normative References . . . . . . . . . . . . . . . . . . . . . 16
Informative References . . . . . . . . . . . . . . . . . . . . 17
Author's Address . . . . . . . . . . . . . . . . . . . . . . . 17
Intellectual Property and Copyright Statements . . . . . . . . 18
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1. Introduction
In multimedia communications, presence and instant messaging systems,
operations are frequently performed on lists of Uniform Resource
Identifiers (URIs). 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. A presence list can also be used
by a user agent that chooses to subscribe to each user in its
presence list, rather than using a list subscription. In such a case,
the client would read the list from local storage, and generate
subscriptions to each member.
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.
There are other applications of resource lists besides presence
lists. Another example is a list of recipients for an instant
message, or a list of users to invite to a conference bridge.
This specification describes a common format for representing such a
list, and for describing the set of actions which may be performed
against the list. Lists can be hierarchical, and can contain
sub-lists referenced by a URI.
Resource list documents can be manipulated by clients using several
means. One such mechanism is the XML Configuration Access Protocol
(XCAP) [7]. This specification defines the details necessary for
using XCAP to manage presence authorization documents.
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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. 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 RFC 3688 [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 an optional "mandatory-ns" element
(defined in XCAP [7]), followed by 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 the "list" element. The first is
"name". This attribute is a descriptive name for the list. It MUST be
unique amongst all other list elements within the same parent
element. It serves as a useful, but optional handle to identify a
list.
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]. This application usage does not provide any
information on which users would be authorized to subscribe to the
list, however.
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 zero or more
elements, each of which may be an "entry" element, a "list" element,
an "entry-ref" element, or an "external" element. 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 URI that is part of the list. An "entry-ref" element allows an
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entry to be included by reference, rather than by value. The content
of "entry-ref" is a URI that points to an "entry" element in this
document or another. This URI MUST be an HTTP URI identifying an XCAP
resource. An "external" element contains a reference to a list stored
on another server. The content of this element MUST also be an HTTP
URI identifying an XCAP resource. 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 two attributes:
name: This optional attribute is a unique identifier amongst all
other "entry" elements of the same parent.
uri: This mandatory 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 "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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4. XML Schema
The following is the XML schema definition of the resource list:
See RFCXXXX.
END Rosenberg Expires August 15, 2004 [Page 14] Internet-Draft XML Resource Lists February 2004 8.4 Resource List Schema Registration This section registers an XML schema per the procedures in [6]. URI: please assign. Registrant Contact: IETF, SIMPLE working group, (simple@ietf.org), Jonathan Rosenberg (jdrosen@jdrosen.net). The XML for this schema can be found as the sole content of Section 4. Rosenberg Expires August 15, 2004 [Page 15] Internet-Draft XML Resource Lists February 2004 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 FirstEdition 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", BCP 81, RFC 3688, January 2004. [7] Rosenberg, J., "The Extensible Markup Language (XML) Configuration Access Protocol (XCAP)", draft-ietf-simple-xcap-01 (work in progress), October 2003. Rosenberg Expires August 15, 2004 [Page 16] Internet-Draft XML Resource Lists February 2004 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 07054 US Phone: +1 973 952-5000 EMail: jdrosen@dynamicsoft.com URI: http://www.jdrosen.net Rosenberg Expires August 15, 2004 [Page 17] Internet-Draft XML Resource Lists February 2004 Intellectual Property Statement The IETF takes no position regarding the validity or scope of any intellectual property or other rights that might be claimed to pertain to the implementation or use of the technology described in this document or the extent to which any license under such rights might or might not be available; neither does it represent that it has made any effort to identify any such rights. Information on the IETF's procedures with respect to rights in standards-track and standards-related documentation can be found in BCP-11. 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