BQM: a system integrating logic, objects, and non-monotonic reasoning

The BQM system extends deductive database technology with knowledge structuring capabilities to provide an advanced environment for the development of data and knowledge-based applications. The system relies on a knowledge representation language that combines the declarativeness of logic programming with the notions of object, inheritance with exceptions and message passing. Exceptions are supported by allowing rules with negated heads. The use of exceptions inside the inheritance mechanism makes the language inherently nonmonotonic. The paper describes BQM focusing on both the language and the implementation techniques. An informal overview of the language is first given. Then, a number of techniques for efficient query evaluation are presented. These techniques significantly extend "traditional" deductive database query evaluation strategies to deal with nonmonotonic reasoning. A description of the architecture of the current prototype of the BQM system is also given.