TriGS - A Trigger System for GemStone

Active object-oriented concepts are especially useful in the area of nonstandard applications in order to express an event-driven and constraint-driven system environment [Chak90, Daya88b, Ahme92]. Several attempts have been made to integrate active concepts into object-oriented databases [Beer91, Daya88a, Diaz91, Gatz91, Geha91, Kim92, Mede91]. Current approaches to active objectoriented database systems, however, do not consider the various active concepts together with some of the basic object-oriented concepts: They do not exploit all the advantages of object-oriented features to make the whole system more expressive and open for changing requirements. Our system called TriGS (=Trigger system for GemStone) tries to make explicit use of object-oriented concepts like objects, messages, inheritance, overriding, and overloading in order to integrate active mechanisms into an existing object-oriented database system. TriGS is implemented on top of the object-oriented database system GemStoneTM [Butt91, Serv91] as part of the EC ESPRIT project ”Design, Development and Implementation of a Knowledge-Based Leitstand (KBL No. 5161)”1 aiming at the development of next-generation production scheduling and control systems.