SIMPLE WG M. Isomaki Internet-Draft Nokia Research Center Expires: November 1, 2004 E. Leppanen Nokia May 3, 2004 An Extensible Markup Language (XML) Configuration Access Protocol (XCAP) Usage for Manipulating Presence Document Contents draft-ietf-simple-xcap-pidf-manipulation-usage-00 Status of this Memo This document is an Internet-Draft and is in full conformance with all provisions of Section 10 of RFC2026. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF), its areas, and its working groups. Note that other groups may also distribute working documents as Internet-Drafts. Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as "work in progress." The list of current Internet-Drafts can be accessed at http:// www.ietf.org/ietf/1id-abstracts.txt. The list of Internet-Draft Shadow Directories can be accessed at http://www.ietf.org/shadow.html. This Internet-Draft will expire on November 1, 2004. Copyright Notice Copyright (C) The Internet Society (2004). All Rights Reserved. Abstract This document describes a usage of the Extensible Markup Language (XML) Configuration Access Protocol (XCAP) for manipulating the contents of Presence Information Data Format (PIDF) based presence document. It is mainly intended to be used in Session Initiation Protocol (SIP) based presence systems, where the Event State Compositor can use the XCAP-manipulated presence document as one of the inputs based on which it builds the overall presence state for the presentity. Isomaki & Leppanen Expires November 1, 2004 [Page 1] Internet-Draft XCAP Usage for Manipulating Presence Document May 2004 Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3 2. Conventions . . . . . . . . . . . . . . . . . . . . . . . . 4 3. Relationship with presence state published using SIP PUBLISH . . . . . . . . . . . . . . . . . . . . . . . . . . 4 4. Application Unique ID . . . . . . . . . . . . . . . . . . . 5 5. Structure of Published Presence Information . . . . . . . . 5 6. Computed Data . . . . . . . . . . . . . . . . . . . . . . . 6 7. Additional Constraints . . . . . . . . . . . . . . . . . . . 6 8. Naming Conventions . . . . . . . . . . . . . . . . . . . . . 6 9. Authorization Policies . . . . . . . . . . . . . . . . . . . 6 10. XML Schema . . . . . . . . . . . . . . . . . . . . . . . . . 6 11. Example Document . . . . . . . . . . . . . . . . . . . . . . 6 12. Security Considerations . . . . . . . . . . . . . . . . . . 7 13. IANA Considerations . . . . . . . . . . . . . . . . . . . . 8 13.1 XCAP Application Usage ID . . . . . . . . . . . . . . . 8 14. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 8 15. References . . . . . . . . . . . . . . . . . . . . . . . . . 8 15.1 Normative References . . . . . . . . . . . . . . . . . . . 8 15.2 Informative References . . . . . . . . . . . . . . . . . . 8 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . 9 Intellectual Property and Copyright Statements . . . . . . . 10 Isomaki & Leppanen Expires November 1, 2004 [Page 2] Internet-Draft XCAP Usage for Manipulating Presence Document May 2004 1. Introduction The Session Initiation Protocol (SIP) for Instant Messaging and Presence (SIMPLE) specifications allow a user, called a watcher, to subscribe to another user, called a presentity [7], in order to learn their presence information [8]. A SIP based mechanism, SIP PUBLISH method, has been defined for publishing presence state [12]. However, SIP PUBLISH has a limited scope and does not address all the requirements for setting presence state. First, it only allows a single Presence User Agent (PUA) to publish its view of the presence state, independently of and without the possibility to learn about the states set by other PUAs. Since each PUA is typically tied to a single physical device, this means that it is hard to set device independent presence state using SIP PUBLISH. Second, SIP PUBLISH creates a soft state which expires after the negotiated lifetime unless it is refreshed. This makes it unsuitable for setting state that should prevail even without active refreshing. There are several use cases where setting of permanent presence state that can be manipulated independent of any device is needed. For instance presentity's e-mail (mailto: URI) and WWW homepage (http: URI) address are this kind of information. Similarly a user might want to set information, such as note, that should constitute his presence in the absence of any active publications, i.e. serve as a sort of default presence state. SIMPLE based presence systems thus require a mechanism to complement SIP PUBLISH in order to address these use cases. XML Configuration Access Protocol (XCAP) [2] allows a client to read, write and modify application configuration data, stored in XML format on a server. The data has no expiration time, so it must be explicitly inserted and deleted. The protocol allows multiple clients to manipulate the data, provided that they are authorized to do so. XCAP is already used in SIMPLE based presence systems for manipulation of presence lists and presence authorization policies. This makes XCAP an ideal choice for doing device independent presence document manipulation. This document defines an XML Configuration Access Protocol (XCAP) application usage for manipulating the contents of presence document. Presence Information Document Format (PIDF) [3] is used as the presence document format, since event state compositor already has to support it, as it is used in SIP PUBLISH. Section 3 describes in more detail how the presence document manipulated with XCAP is related to soft state publishing done with SIP PUBLISH. Isomaki & Leppanen Expires November 1, 2004 [Page 3] Internet-Draft XCAP Usage for Manipulating Presence Document May 2004 XCAP requires application usages to standardize several pieces of information, including an application unique ID (AUID), and an XML schema for the manipulated data. These are specified starting from the Section 4. 2. Conventions 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. Comprehensive terminology of presence and event state publishing is provided in [12]. 3. Relationship with presence state published using SIP PUBLISH The framework for publishing presence state is introduced in [11]. A central part of the framework is the event state compositor element whose function is to compose presence information received from several sources into a single coherent presence document. The presence state manipulated with XCAP can be seen as one of the information sources for the compositor to be combined with the soft state information published using SIP PUBLISH. This is illustrated in Figure 1. It is expected that in the normal case there can be several PUAs publishing their separate views with SIP PUBLISH, but only single XCAP manipulated presence document. As shown in the figure, there can be multiple XCAP clients (for instance in different physical devices) manipulating the same document on the XCAP server, but this still creates only one input to the event state compositor. As individual inputs the presence states set by XCAP and SIP PUBLISH are completely separated and it is not possible to directly manipulate the state set by one mechanism with the other. How the compositor treats XCAP based inputs with respect to SIP PUBLISH based inputs is a matter of compositor policy, which is beyond the scope of this specification. Since the SIP PUBLISH specification already mandates the compositor to be able to construct the overall presence state from multiple inputs which may contain non-orthogonal (or in some ways even conflicting) information, this XCAP usage does not impose any new requirements on the compositor functionality. One reasonable compositor policy is that the XCAP manipulated presence document is used as the default presence state in absence of any soft state set by SIP PUBLISH, and the soft state augments or overrides the default state. Isomaki & Leppanen Expires November 1, 2004 [Page 4] Internet-Draft XCAP Usage for Manipulating Presence Document May 2004 +---------------+ +------------+ | Event State | | Presence |--> SIP SUBSCRIBE | Compositor +---------+ Agent |<-- SIP NOTIFY | | | (PA) | +-------+-------+ +------------+ ^ ^ ^ | | | | | | +---------------+ +--------+ | +-------| XCAP server | | | +-------+-------+ | | ^ ^ | SIP Publish | | XCAP | | | | | +--+--+ +--+--+ +-------+ +-------+ | PUA | | PUA | | XCAP | | XCAP | | | | | | client| | client| +-----+ +-----+ +-------+ +-------+ Figure 1: Framework for Presence Publishing and Event State Composition The exact protocol interface between XCAP server and the event state compositor is not specified here. The obvious requirement is that such interface exists, and that the presentity indeed has an XCAP server supporting the usage defined in this specification provisioned for him. 4. 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 'pidf-manipulation' AUID within the IETF tree, via the IANA registration in the Section 13. 5. Structure of Published Presence Information The XML [6] format of the presence information (PIDF) is defined in [3] and its extensions. The PIDF defines the presence information to consist of the root element 'presence' including 'tuples' which contain a mandatory status element, a communication mean specific presence attribute and other markups. Additionally, the presence information can contain other presentity level information outside tuples. The namespace URI for PIDF is defined in [3]. Isomaki & Leppanen Expires November 1, 2004 [Page 5] Internet-Draft XCAP Usage for Manipulating Presence Document May 2004 6. Computed Data There are no computed data on the document beyond those described in the schema. 7. Additional Constraints There are no constraints on the document beyond those described in the XML schemas and [3]. 8. Naming Conventions There are no naming conventions beyond the possible conventions defined in [3] that need to be defined for this application usage. 9. Authorization Policies This application usage does not modify the default XCAP authorization policy, which allows only a user (owner) to read, write or modify their own documents. A server can allow privileged users to modify documents that they don't own, but the establishment and indication of such policies is outside the scope of this document. 10. XML Schema The XML schema definition for the presence information can be found from [3] and its extensions. 11. Example Document The following example document illustrates the situation where the (human) presentity has left for vacation, and before that has set his presence state such that he is only available via cellular phone and e-mail. In the absence of any published soft state information, this would be the sole input to the compositor forming the presence document. The example document contain PIDF extensions specified in [9] and [10]. Isomaki & Leppanen Expires November 1, 2004 [Page 6] Internet-Draft XCAP Usage for Manipulating Presence Document May 2004 open Vacation auth-A presentity http://www.example.com/~someone 2004-02-06T16:49:29Z I'm available only by e-mail and GSM phone. open auth-1 service cellphone tel:+358506767 open auth-1 service I'm reading mail a couple of times a week mailto:someone@example.com 12. Security Considerations Presence document may contain information that is highly sensitive. Its delivery to watchers needs to happen strictly according to the relevant authorization policies. It is also important that only authorized clients are able to manipulate the presence information. XCAP base specification mandates that all XCAP servers MUST implement HTTP digest [4]. Furthermore, XCAP servers MUST implement HTTP over TLS [5]. It is recommended that administrators of XCAP servers use an HTTPS URI as the XCAP root services URI, so that the digest client authentication occurs over TLS. By using these means, XCAP client and server can ensure the confidentiality and integrity of the XCAP Isomaki & Leppanen Expires November 1, 2004 [Page 7] Internet-Draft XCAP Usage for Manipulating Presence Document May 2004 presence document manipulation operations, and that only authorized clients are allowed to perform them. 13. IANA Considerations There are an IANA consideration associated with this specification. 13.1 XCAP Application Usage ID This section registers a new XCAP Application Usage ID (AUID) according to the IANA procedures defined in [2]. Name of the AUID: pidf-manipulation Description: Pidf-manipulation application usage defines how XCAP is used to manipulate the contents of presence documents in Session Initiation Protocol (SIP) based presence systems. 14. Acknowledgements The authors would like to thank Jonathan Rosenberg, Aki Niemi, Krisztian Kiss, Jose Costa-Requena and George Foti for their comments. 15. References 15.1 Normative References [1] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997. [2] Rosenberg, J., "The Extensible Markup Language (XML) Configuration Access Protocol (XCAP)", draft-rosenberg-simple-xcap-02 (work in progress), February 2004. [3] Sugano, H., "CPIM presence information data format", draft-ietf-impp-cpim-pidf-08 (work in progress), May 2003. [4] Franks, J., "HTTP Authentication: Basic and Digest Access Authentication", RFC 2617, June 1999. [5] Rescorla, E., "HTTP Over TLS", RFC 2818, May 2000. 15.2 Informative References [6] Bray, T., "Extensible Markup Language (XML) 1.0 (Second edition)", W3C REC REC-xml-20001006, October 2000. Isomaki & Leppanen Expires November 1, 2004 [Page 8] Internet-Draft XCAP Usage for Manipulating Presence Document May 2004 [7] Day, M., "A model for presence and instant messaging", RFC 2778, February 2000. [8] Rosenberg, J., "Session Initiation Protocol (SIP) Extensions for Presence", draft-ietf-simple-presence-10.txt (work in progress), January 2003. [9] Schulzrinne, H., "RPID: Rich Presence: Extension to the Presence Information Data Format", draft-ietf-simple-rpid-03.txt (work in progress), March 2004. [10] Schulzrinne, H., "CIPID: Contact Information in Presence Information Data Format", draft-ietf-simple-cipid-01.txt (work in progress), March 2004. [11] Campbell, B., "SIMPLE Presence Publication Requirements", draft-ietf-simple-publish-reqs-00 (work in progress), February 2003. [12] Niemi, A., "An Event State Publication Extension for Session Initiation Protocol (SIP)", draft-ietf-sip-publish-03.txt (work in progress), February 2004. Authors' Addresses Markus Isomaki Nokia Research Center Itamerenkatu 11-13 00180 Helsinki Finland Phone: EMail: markus.isomaki@nokia.com Eva Leppanen Nokia P.O BOX 785 Tampere Finland Phone: EMail: eva-maria.leppanen@nokia.com Isomaki & Leppanen Expires November 1, 2004 [Page 9] Internet-Draft XCAP Usage for Manipulating Presence Document May 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. 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