Q: How do I handle authorization information?
A: Authorization is handled via XCAP, which is stored in 'xcap_xml' table for each user. If there is no XCAP file for presentity, the subscription will be allowed.
Q: Where can I find an XCAP server that works together with OpenSER presence agent?
A: An XCAP server that works out of the box with OpenSER presence agent is OpenXCAP server from AG Projects.
Q: If I use stand alone presence server I have to forward publish and subscribe requests to the presence server. If I use client-client presence model and the main sip server is same, How do you handle this?
A: Somehow you should be able sort the users with different presence implementation, either you know user's devices (because you admin them or whatsoever) or you can check if the destination has a record in 'presentity' table. The roadmap has the item to be able to convert client-to-client NOTIFY in server-to-client NOTIFY, so the presence server can handle both cases transparently.