Palopoli and Torlone : Generalized Production Rules for Active and Deductive

| We address the problem of providing a homogeneous framework for integrating, in a database environment, active rules, which allow the speciication of actions to be executed whenever certain events take place, and deductive rules, which allow the speciication of deductions in a logic programming style. Actually, it is widely recognized that both kinds of rules enhance the capabilities of database systems as they provide very natural mechanisms for the management of various important activities (e.g., knowledge representation , complex data manipulation, integrity constraint enforcement, view maintenance). In spite of their strong relationship however, little work has been done on the uniica-tion of these powerful paradigms. In this paper, we present a rule-based language with an event-driven semantics that allows the programmers to express both active and deduc-tive computations. The language is based on a new notion of production rule whose eeect is both a change of state and an answer to a query. By using several examples, we show that this simple language schema allows us to uniformly de-ne diierent computations on data, including complex data manipulations, deductive evaluations and active rule processing. We deene the semantics of the language and then describe the architecture of a preliminary implementation of the language. Finally, we report about application and experience of use of the language.