1. A system for processing triggering rules in 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 subscribers 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; and 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.