Information flow based event distribution middleware

Event distribution middleware supports the integration of distributed applications by accepting events from information producers and disseminating applicable events to interested consumers. We present a flexible new model, the Information Flow Graph (IFG), for specifying the flow of information in such a system. We illustrate the use of the IFG for: content-based publish/subscribe; stateless event transformations that consolidate events from diverse sources; and stateful event interpretation functions for deriving trends, summaries, and alarms from published events and for defining equivalent event sequences. We introduce two techniques for efficient implementation of such systems: a flow graph rewriting optimization which allows stateless IFGs to be converted to a form which can exploit efficient multicast technology developed for content-based publish/subscribe system; and an algorithm for converting a sequence of events to the shortest equivalent sequence of events with respect to an event interpretation function.