Composite Event Specification in Active Databases: Model and Implementation

Active database systems require facilities to specify triggers that are fired when composite events, specified in terms of other (primitive) events, occur. We propose a language for specifying composite events as event expressions, formed using event operators to compose multiple events. An event expression maps an event history to another event history that contains only the events at which the event expression is satisfied and the trigger should fire. We present several examples illustrating how quite complex event specifications are possible using event expressions.