Active database systems require facilities to specify triggers that fire when specified events occur. We propose a language for specifying composite events as eveti expressions, formed using event operators and events (primitive or composite). An event expression maps an event history to anothe-r event history that contains only the events at which the event expression is “satisfied ” and at which the trigger should 6re. We present several examples illustrating how quite complex event specifications are possible using event expressions. In addition to the basic event operators, we also provide facilities that make it easier to specify composite events. “Pipes ” allow users to isolate sub-histories of interest. “Correlation variables ” allow users to ensure that different parts of an event expression are satisfied by the same event,

The concept of a trigger is central to any active database. Upon the occurrence of a trigger event, the trigger is ‘‘fired’’, i.e, the trigger action is executed. We describe a model for specifying basic and composite trigger events in the context of an object-oriented database. We integrate our model with O , the database programming language for the Ode object database being developed at AT

Founding on our experience with active database technology in a relational setting we now advance with the integration of the event driven paradigm into object-oriented databases. We develop an execution model for a language that explicitly allows for both, procedural and eventdriven behaviour. Whereas procedural behaviour via methods describes a close interaction of objects the event-driven behaviour reflects a loose coupling of objects, i.e. objects perform some actions due to events in the system they learn about. This paper presents the architecture and the execution model of the active runtime system ARTS. ARTS supports active database applications with interacting autonomous objects in the sense described above. Autonomous objects communicate via the novel concept of a network of channels that are adaptable to the complexity of the applications. ARTS is the object-oriented core of our active information systems development environment AIDE realised in the A.I.S. (Active...