Query Evaluation in Deductive Databases with Alternating Fixpoint Semantics

First-order formulas allow natural descriptions of queries and rules. Van Gelder's alternating fixpoint semantics extends the well-founded semantics of normal logic programs to general logic programs with arbitrary first-order formulas in rule bodies. However, an implementation of general logic programs through the standard translation into normal logic programs does not preserve the alternating fixpoint semantics. This paper presents a direct method for goal-oriented query evaluation of general logic programs. Every general logic program is first transformed into a normal form where the body of each rule is either an existential conjunction of literals or a universal disjunction of literals. Techniques of memoing and loop checking are incorporated so that termination and polynomial time data complexity are guaranteed for deductive databases (or function-free programs). Results of the soundness and search space completeness are established