Composite Event Management in TriGS - Concepts and Implementation

Active object-oriented database systems are a commonly accepted solution for capturing the timeand context-dependent knowledge of non-standard applications. Several attempts have been made already to integrate active concepts into object-oriented database systems and to increase the expressive power of event specification languages. However, this has often been done without considering the consequences for the implementation. The present paper tries to fill this gap. The main focus is on describing implementational issues concerning composite event management within the active object-oriented database system TriGS. One emphasize is put on the representation of composite events by means of extended syntax graphs, realizing different kinds of event operators, guards and contexts. In this respect TriGS allows for an unrestricted life-span of events. With this it is possible to detect composite events spanning several transactions and even several applications. Another focus is on the smooth integration of composite event detection and rule scheduling. Finally, a major part of the paper is dedicated to mechanisms realizing both, full and selective inheritance of rules. With this, rules containing message events do not only monitor the behavior of the class they are related to but rather are able to monitor the behavior of the whole class hierarchy.