1. Markus Isomäki Eva Leppänen
XCAP Usage for Publishing Presence Information draft-isomaki-simple-xcap-publish-usage-00
Markus Isomäki
Eva Leppänen

2. 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 address
Note ”I’m on holiday without any connectivity for the next 3 weeks”

3. 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

4. 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

5. 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 |

6. 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

7. 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