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XCAP Usage for Publishing Presence Information draft-isomaki-simple-xcap-publish-usage-00. Markus Isomäki Eva Leppänen. Motivation. SIP PUBLISH allows a particular PUA to publish its view of the presentity, separate from other views published by other PUAs
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XCAP Usage for Publishing Presence Informationdraft-isomaki-simple-xcap-publish-usage-00 Markus Isomäki Eva Leppänen
Motivation • SIP PUBLISH allows a particular PUA to publish its view of the presentity, separate from other views published by other PUAs • It is not possible for other PUAs to fetch this information • The data published using SIP PUBLISH is always associated with an expiration time • Infinite expiration time has issues with state cleanup etc. • There is a need to be able to publish PUA/device independent data about the presentity • Parts of this data change very infrequently • It must be possible to fetch and update this data from any device • Examples of this kind of data • Presentity’s homepage • Presentity’s e-mail address • Note ”I’m on holiday without any connectivity for the next 3 weeks”
Why XCAP? • Using XCAP seems like an obvious solution • XCAP allows manipulation of XML-based data on a server • Multi-client support • Partial updates • Presence data is XML-based • SIMPLE Presence applications already use XCAP to manipulate lists and presence authorization policies • This was also consensus on SIMPLE WG mailing list publishing discussion and during SIMPLE WG session at IETF #57
What the Draft Specifies • Actually, there is very little to specify • AUID ”presence-publish” • PIDF XML schema and its extensions (RPID, CIPID, Prescaps, …) • No computed data or additional constraints • Basic XCAP/HTTP PUT, GET, DELETE operations take care of the rest
Co-Existence with SIP PUAs +---------------+ +------------+ | Event State | | Presence |<-- SIP SUBSCRIBE | Compositor +---------+ Agent |--> SIP NOTIFY | | | (PA) | +-------+-------+ +------------+ | | | +---------------+ +--------------^-------------| XCAP server | | | +-------+-------+ | | ^ | SIP Publish | | XCAP Publish | | | +--+--+ +--+--+ +--------+--------------+ | PUA | | PUA | | XCAP presence-publish | | | | | | clients | +-----+ +-----+ +-----------------------+
Open Issues • How to publish content which is ”external” to PIDF? • Images, logos etc. • Proposal: • Upload external content via HTTP • Insert the HTTP URI to PIDF document • Allow the Presence Agent to include this content into NOTIFY as a separate MIME part, replacing the HTTP URI with the corresponding CID URI • PA can as well leave the HTTP URI unmodified, if the URI is accessible by the watchers
Next Steps • Adopt this as WG draft • Submit a new version shortly • Improve the motivation section • Make recommendations when to use SIP PUBLISH and when XCAP • Improve the language in general