5. A system for processing triggering rules in Session Initiation Protocol (SIP) event notification filters, the system comprising: an XPath processor configured to collect a set of XPath expressions from at least one trigger of at least one SIP event notification filter of at least one subscriber in a set of subscribers who are subscribed to state information of a resource, and create a merged finite state automaton having a plurality of nodes and transitions that collectively represent the combination of said XPath expressions; a processor for executing a streaming parser configured to parse previously-published state information of said resource and newly-published state information of said resource, and stream parsing events of said parsed information to said XPath processor, wherein said XPath processor is configured to employ said automaton to perform a streaming evaluation of said XPath expressions in parallel to determine which nodes of said parsed information satisfies any of said XPath expressions represented by said automaton, and wherein said XPath processor is configured to derive a value from either of said previously-published state information and said newly-published state information, said value being associated with said any of said XPath expressions; and a trigger condition evaluator configured to evaluate, for any of said filters, all of said values of all of said trigger conditions that determine whether a notification is to be sent, and compose and send said notification if said evaluated trigger conditions are met.
5. A system for processing triggering rules in Session Initiation Protocol (SIP) event notification filters, the system comprising: an XPath processor configured to collect a set of XPath expressions from at least one trigger of at least one SIP event notification filter of at least one subscriber in a set of subscribers who are subscribed to state information of a resource, and create a merged finite state automaton having a plurality of nodes and transitions that collectively represent the combination of said XPath expressions; a processor for executing a streaming parser configured to parse previously-published state information of said resource and newly-published state information of said resource, and stream parsing events of said parsed information to said XPath processor, wherein said XPath processor is configured to employ said automaton to perform a streaming evaluation of said XPath expressions in parallel to determine which nodes of said parsed information satisfies any of said XPath expressions represented by said automaton, and wherein said XPath processor is configured to derive a value from either of said previously-published state information and said newly-published state information, said value being associated with said any of said XPath expressions; and a trigger condition evaluator configured to evaluate, for any of said filters, all of said values of all of said trigger conditions that determine whether a notification is to be sent, and compose and send said notification if said evaluated trigger conditions are met. 6. A system according to claim 5 wherein any of said XPath processor, said streaming parser, and said trigger condition evaluator are executable by a computer.