[Serusers] presence server 2 presence server

Hi, I am student and new to the Presence Model und Protocols. I have in my student project the following scenario: company A wants to develop a presence service PA. The presence service PA should get the data from the presence server PB of an other Company B over the Internet. The Presence information of PA should be made available in the Company A for different applications. my question: can PA poll or subscribe all changed/updated Presence Information from PB regularly. Or it should request the Presence Information of each Presentity individually? which Presence server can implement the presence service PA. What should I do if PB uses another Protokoll? Thank you and Best Regards Koder -- Psssst! Schon vom neuen GMX MultiMessenger gehört? Der kanns mit allen: http://www.gmx.net/de/go/multimessenger