Expressiveness Issues and Decision Problems for Active Database Event Queries
نویسندگان
چکیده
A key facility of active database management systems is their ability to detect and react to the occurrence of events. Such events can be either atomic in nature, or speciied using an event algebra to form complex events. An important role of an event algebra is to deene the semantics of when events become invalid (event consumption). In this paper, we examine a simple event algebra and provide a logical framework for speciication of various consumption policies. We then study the problems of equivalence and implication, identifying a powerful class of complex events for which equivalence is decidable. We then demonstrate how extensions of this class lead to undecidability.
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