Formal Semantics for Composite Temporal Events in Active Database Rules

A major thrust of current research in active databases focuses on allowing complex patterns of temporal events to serve as preconditions for rule triggering. Currently, there is no common formalism for specifying the semantics of composite event languages. Different systems have used an assortment of different techniques, including Finite State Automata, Petri Nets and Event Graphs. In this paper, we propose a unifying approach, based on a syntax-directed translation of composite event expressions into Datalog1S rules, whose formal semantics defines the meaning of the original expressions. We demonstrate our method by providing a formal specification of the Event Pattern Language (EPL) developed at UCLA. This method overcomes problems and limitations affecting previous approaches and is applicable to other languages such as ODE, SNOOP and SAMOS—thus, allowing a more direct comparison across different systems.

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