Generalized query answering in disjunctive databases using minimal model generation

Abstract

Minimal models underly one of the major semantics for disjunctive theories and a substantial research e ort was directed at minimal model reasoning. In this paper we investigate the process of generalized query answering under the minimal model semantics for the class of Disjunctive Deductive Databases. We cover several classes of queries that are of practical importance for database maintenance. Answers that are true in al l and those that are true in some minimal models of the theory are considered and their monotonicity properties are discussed. Our approach is based on having the generalized query induce an order on the models returned by a sound and complete minimal model generating procedure. This makes it possible to introduce re nements to the query answering process such as allowing the speci cation of conditions under which a query becomes derivable from the database and checking for answer minimality.