The Ode active database: trigger semantics and implementation

Ode is an active database system and environment based on the object paradigm. Triggers are the basic ingredient of active databases. Ode triggers are event-action pairs. An event can be a composite event (i.e. an event composed from other events). Composite events are detected by translating the event specifications into finite state machines. In this paper, we describe the integration and implementation of composite event-based triggers into the Ode object database. We focus on implementation details such as the basic trigger events supported, the efficient posting of these events, the handling of transaction-related events and the integration of triggers into a real database. We also describe the run-time facilities used to support trigger processing and describe some experiences we gained while implementing triggers. We illustrate Ode trigger facilities with a credit card example.