Specifying Event Logics for Active Databases

Active databases are usually centered around the notion of Event-Condition-Action (ECA) rules. An ECA rule’s action is executed upon detection of an event whenever the rule’s condition is true. Events are traditionally described using an event algebra. Virtually every proposed active database management system (ADBMS) brings about a different event algebra. This makes it very difficult to analyze these proposals in a uniform way by spelling out what they may have in common, or how they may differ. Typically, logic might act as a framework for dealing with these issues. This paper treats events as (somewhat constrained) formulas of the situation calculus, a (second order) logic for reasoning about actions in general, and database updates and transactions in particular. We provide a framework for devising the semantics of complex events in this logic. Such semantics, formulated as theories of a special kind, are used for reasoning about the occurrence and consumption modes, which are an important dimension of events.