SIMPLE WG M. Isomaki Internet-Draft E. Leppanen Expires: April 22, 2005 Nokia October 22, 2004 An Extensible Markup Language (XML) Configuration Access Protocol (XCAP) Usage for Manipulating Presence Document Contents draft-ietf-simple-xcap-pidf-manipulation-usage-02 Status of this Memo This document is an Internet-Draft and is subject to all provisions of section 3 of RFC 3667. By submitting this Internet-Draft, each author represents that any applicable patent or other IPR claims of which he or she is aware have been or will be disclosed, and any of which he or she become aware will be disclosed, in accordance with RFC 3668. 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 April 22, 2005. Copyright Notice Copyright (C) The Internet Society (2004). 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 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 on Isomaki & Leppanen Expires April 22, 2005 [Page 1] Internet-Draft XCAP Usage for Manipulating Presence Document October 2004 which it builds the overall presence state for the presentity. Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3 2. Conventions . . . . . . . . . . . . . . . . . . . . . . . . 4 3. Relationship with Presence State Published Using SIP PUBLISH . . . . . . . . . . . . . . . . . . . . . . . . . . 4 4. Application Usage ID . . . . . . . . . . . . . . . . . . . . 6 5. Structure of Manipulated Presence Information . . . . . . . 6 6. Additional Constraints . . . . . . . . . . . . . . . . . . . 6 7. Resource Interdependencies . . . . . . . . . . . . . . . . . 6 8. Naming Conventions . . . . . . . . . . . . . . . . . . . . . 6 9. Authorization Policies . . . . . . . . . . . . . . . . . . . 6 10. Example Document . . . . . . . . . . . . . . . . . . . . . . 6 11. Security Considerations . . . . . . . . . . . . . . . . . . 8 12. IANA Considerations . . . . . . . . . . . . . . . . . . . . 8 12.1 XCAP Application Usage ID . . . . . . . . . . . . . . . 8 13. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 9 14. References . . . . . . . . . . . . . . . . . . . . . . . . . 9 14.1 Normative References . . . . . . . . . . . . . . . . . . . 9 14.2 Informative References . . . . . . . . . . . . . . . . . . 9 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . 10 Intellectual Property and Copyright Statements . . . . . . . 11 Isomaki & Leppanen Expires April 22, 2005 [Page 2] Internet-Draft XCAP Usage for Manipulating Presence Document October 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, in order to learn their presence information [7]. The presence data model has been specified in [10]. The data model makes a clean separation between person, service and device related information. A SIP based mechanism, SIP PUBLISH method, has been defined for publishing presence state [4]. Using SIP PUBLISH a Presence User Agent (PUA) can publish its view of the presence state, independently of and without the need to learn about the states set by other PUAs. However, SIP PUBLISH has a limited scope and does not address all the requirements for setting presence state. The main issue is that SIP PUBLISH creates a soft state which expires after the negotiated lifetime unless it is refreshed. This makes it unsuitable for cases where the state should prevail without active devices capable of refreshing the state. There are three main use cases where setting of permanent presence state that is independent of activeness of any particular device is useful. The first case concerns setting person related state. The presentity would often like to set its presence state even for periods when it has no active devices capable of publishing available. Good examples are traveling, vacations and so on. The second case is about setting state for services that are open for communication even if the presentity does not have a device running that service on-line. Examples of this kind of services include e-mail, MMS and SMS. In these services the presentity is provisioned with a server that makes the service persistently available, at least in certain form, and it would be good to be able to advertise this to the watchers. Since it is not realistic to assume that all e-mail, MMS or SMS servers can publish presence state on their own (and even if this were possible, such state would almost never change), this has to be done by some other device - and since the availability of the service is not dependent on that device, it would be unpractical to require that device to be constantly active just to publish such availability. The third case concerns setting the default state of person, any service or any device in the absence of any device capable of actively publishing such state. For instance the presentity might want to advertise that his or her voice service is right now closed, just to let the watchers to know that such service might be open at some point. Again, this type of default state is independent of any particular device, and can be considered to be rather persistent. Even though SIP PUBLISH remains to be the main way of publishing Isomaki & Leppanen Expires April 22, 2005 [Page 3] Internet-Draft XCAP Usage for Manipulating Presence Document October 2004 presence state in SIMPLE based presence systems and is espcially well suited for publishing dynamic state (which presence mainly is), it needs to be complemented by the mechanism described in this document to address the use cases presented above. 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. XCAP requires application usages to standardize several pieces of information, including a unique application usage ID (AUID), and an XML schema for the manipulated data. These are specified starting from 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 Session Initiation Protocol (SIP) Extension for Event State Publication [4]. 3. Relationship with Presence State Published Using SIP PUBLISH The framework for publishing presence state is described in Figure 1. 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. Isomaki & Leppanen Expires April 22, 2005 [Page 4] Internet-Draft XCAP Usage for Manipulating Presence Document October 2004 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 a 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. +---------------+ +------------+ | 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 protocol interface between XCAP server and the event state compositor is not specified here. Isomaki & Leppanen Expires April 22, 2005 [Page 5] Internet-Draft XCAP Usage for Manipulating Presence Document October 2004 4. Application Usage 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 12. 5. Structure of Manipulated Presence Information The XML Schema of the presence information (PIDF) is defined in CPIM Presence Information Data Format [3]. The PIDF also defines a mechanism for extending presence information. See [8], [9], [11] and [12] for currently defined PIDF extensions and their XML Schemas. The namespace URI for PIDF is 'urn:ietf:params:xml:ns:pidf'. 6. Additional Constraints There are no constraints on the document beyond those described in the XML schemas (PIDF and its extensions) and in the description of CPIM PIDF [3]. 7. Resource Interdependencies There are no resource interdependencies beyond the possible interdependencies defined in CPIM PIDF [3] and XCAP [2] that need to be defined for this application usage. 8. Naming Conventions There are no naming conventions beyond the possible conventions defined in CPIM PIDF [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 do not own, but the establishment and indication of such policies is outside the scope of this document. 10. Example Document The section provides an example of presence document provided by an XCAP Client to an XCAP Server. The presence document illustrates the situation where a (human) presentity has left for vacation, and before that has set his presence information such that he is only Isomaki & Leppanen Expires April 22, 2005 [Page 6] Internet-Draft XCAP Usage for Manipulating Presence Document October 2004 available via 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 RPID: Rich Presence Extensions to the Presence Information Data Format (PIDF) [8] and CIPID: Contact Information in Presence Information Data Format [9]. First, the presence document is created. PUT http://xcap.example.com/services/pidf-manipulation/users/someone/pidf.xml HTTP/1.1 Content type:appliation/pidf+xml closed auth-1 sip:user@example.com I'm available only by e-mail. 2004-02-06T16:49:29Z open auth-1 mailto:someone@example.com I'm reading mail a couple of times a week auth-A http://www.example.com/~someone Vacation Isomaki & Leppanen Expires April 22, 2005 [Page 7] Internet-Draft XCAP Usage for Manipulating Presence Document October 2004 HTTP/1.1 201 Created Etag: "xyz" Next, the note concerning the e-mail is changed. PUT http://xcap.example.com/services/pidf-manipulation/users/someone/pidf.xml /~~/presence/tuple%5b@id=%228eg92n%22%5d/note HTTP/1.1 If-Match: "xyz" Content type:appliation/xcap-el+xml I'm reading mails on Tuesdays and Fridays HTTP/1.1 200 OK Etag:"xyzz" 11. Security Considerations A 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. The XCAP base specification mandates that all XCAP servers MUST implement HTTP Digest authentication specified in RFC 2617 [5]. Furthermore, XCAP servers MUST implement HTTP over TLS [6]. 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 presence document manipulation operations, and that only authorized clients are allowed to perform them. 12. IANA Considerations There is an IANA consideration associated with this specification. 12.1 XCAP Application Usage ID This section registers a new XCAP Application Usage ID (AUID) Isomaki & Leppanen Expires April 22, 2005 [Page 8] Internet-Draft XCAP Usage for Manipulating Presence Document October 2004 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 PIDF based presence documents. 13. Acknowledgements The authors would like to thank Jonathan Rosenberg, Hisham Khartabil, Aki Niemi, Mikko Lonnfors, Oliver Biot, Alex Audu, Krisztian Kiss, Jose Costa-Requena, George Foti and Paul Kyzivat for their comments. 14. References 14.1 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-ietf-simple-xcap-03 (work in progress), July 2004. [3] Sugano, H., "CPIM presence information data format", draft-ietf-impp-cpim-pidf-08, May 2003. [4] Niemi, A., "An Event State Publication Extension for Session Initiation Protocol (SIP)", draft-ietf-sip-publish-04.txt, May 2004. [5] Franks, J., "HTTP Authentication: Basic and Digest Access Authentication", RFC 2617, June 1999. [6] Rescorla, E., "HTTP Over TLS", RFC 2818, May 2000. 14.2 Informative References [7] Rosenberg, J., "A Presence Event Package for the Session Initiation Protocol (SIP)", RFC 3856, August 2004. [8] Schulzrinne, H., "RPID: Rich Presence Extensions to the Presence Information Data Format (PIDF)", draft-ietf-simple-rpid-03.txt (work in progress), March 2004. [9] Schulzrinne, H., "CIPID: Contact Information in Presence Information Data Format", draft-ietf-simple-cipid-03.txt (work in progress), July 2004. Isomaki & Leppanen Expires April 22, 2005 [Page 9] Internet-Draft XCAP Usage for Manipulating Presence Document October 2004 [10] Rosenberg, J., "A Data Model for Presence", draft-ietf-simple-presence-data-model-00 (work in progress), September 2004. [11] Lonnfors, M., "User Agent Capability Extension to Presence Information Data Format (PIDF)", draft-ietf-simple-prescaps-ext-01 (work in progress), May 2004. [12] Schulzrinne, H., "Timed Presence Extensions to the Presence Information Data Format (PIDF) to Indicate Presence Information for Past and Future Time Intervals", draft-ietf-simple-future-02 (work in progress), July 2004. Authors' Addresses Markus Isomaki Nokia P.O.BOX 100 00045 NOKIA GROUP Finland Phone: EMail: markus.isomaki@nokia.com Eva Leppanen Nokia P.O BOX 785 33101 Tampere Finland Phone: EMail: eva-maria.leppanen@nokia.com Isomaki & Leppanen Expires April 22, 2005 [Page 10] Internet-Draft XCAP Usage for Manipulating Presence Document October 2004 Intellectual Property Statement The IETF takes no position regarding the validity or scope of any Intellectual Property Rights 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; nor does it represent that it has made any independent effort to identify any such rights. Information on the procedures with respect to rights in RFC documents can be found in BCP 78 and BCP 79. 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