Expressiveness issues and decision problems for active database event queries
J Bailey, S Mikulás
Lecture Notes in Computer Science (including subseries Lecture Notes in Artificial Intelligence and Lecture Notes in Bioinformatics) | Published : 2001
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 specified using an event algebra to form complex events. An important role of an event algebra is to define the semantics of when events become invalid (event consumption). In this paper, we examine a simple event algebra and provide a logical framework for specification 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.