PROCESSING PRODUCTION RULES IN DEVICE, AN ACTIVE KNOWLEDGE-BASE SYSTEM

Production rules are useful for several tasks in active database syste ms, such as integrity constraint checking, derived data maintenance, d atabase state monitoring, etc. Furthermore, production rules can expre ss knowledge in a high-level form for problem solving in Knowledge Bas e Systems (KBS). Present active object-oriented database (OODB) system s traditionally provide event-driven rules which are triggered by even ts, i.e. database modifications. This paper describes DEVICE, a high-l evel rule integration scheme in an active OODB system, resulting in an active KBS. The paper emphasises the run-time processing of productio n rules, namely the incremental matching of rule conditions, as well a s rule selection and firing. The matching of production rules requires special algorithms based on the flow of updated data through a discri mination network, like PETE, TREAT, etc. DEVICE offers a smooth integr ation of production rules into an active OODB system that only support s event-driven rules, without introducing new data structures, maintai ning at the same time the properties of discrimination networks. This is achieved using complex events to map the conditions of production r ules and monitor the database to incrementally match those conditions. DEVICE maps each production rule into one event-driven rule that is e asy to maintain and offers centralised rule selection control for corr ect run-time behaviour and conflict resolution. Furthermore, DEVICE pr ovides the infrastructure for the integration of various other rule pa radigms into a single KBS, like deductive rules and integrity constrai nts and leaves room for the optimisation of the matching process throu gh variations of the basic discrimination network.