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. In this paper 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: (1) content-based publish/subscribe; (2) stateless event transformations that consolidate events from diverse sources; and (3) 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: (1) 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 systems; and (2) an algorithm for converting a sequence of events to the shortest equivalent sequence of events with respect to an event interpretation function.