Session Initiation Protocol (SIP) Extension for Partial Notification of Presence Information

By default, presence delivered using the Presence Event Package for the Session Initiation Protocol (SIP) is represented in the Presence Information Data Format (PIDF). A PIDF document contains a set of elements, each representing a different aspect of the presence being reported. When any subset of the elements change, even just a single element, a new document containing the full set of elements is delivered. This memo defines an extension allowing delivery of only the presence data that has actually changed.