OLAF: The GOAD Active Database event/rule tracer

In this paper we discuss OLAF, a tracing tool that we have developed which enables the active database designer to watch the flow of events and rules through our Active Database system (GOAD). We shall show how we use active rules to halt the execution of active components that we wish to trace, and demonstrate how our emphasis on generality of design enables us to trace each type of active component (i.e. primitive events, composite events, rules etc.) without making any additional changes to the tracer. We shall discuss the OLAF tracer itself, showing the facilities it provides and how it is integrated with the rest of the GOAD toolset.