Generalized production rules as a basis for integrating active and deductive databases

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