EXACT: An Approach to Coping with Heterogeneous Rule Execution Models

Abstract

The large and heterogeneous range of applications that are being supported through rules requires the availability of flexible rule systems that are easy to tailor to application requirements. Such requirements affect not only how rules are described, but also how rules are handled at execution time. Indeed, a substantial part of the application semantics is realized through the rule execution model. While flexible knowledge models can be accomplished by supporting rules as first-class objects, it has been far from clear how to obtain flexible execution models. This chapter describes the EXACT approach, an active DBMS where the execution model is defined as part of the rule class definition, so that the designer can choose the rule execution strategy that best fits the application at hand.