An Alternative Characterization of Disjunctive Logic Programs

Abstract

\indent We present an alternative characterization of disjunctive logic programs. We first review Inheritance near-Horn Prolog (InH-Prolog), an intuitive and computationally effective procedure that extends Prolog using case-analysis. We then describe a fixpoint characterization of disjunctive logic programs that is similarly based on case-analysis. This fixpoint characterization closely corresponds to the InH-Prolog procedure, and so gives needed insight into the difficult problem of recognizing the minimal disjunctive answers obtainable from the procedure. Due to its case-analysis nature, this characterization maintains a natural and close relationship to the standard characterization of Horn program. It also gives added insight into the role of definite answers for disjunctive programs and enables one to neatly focus attention on the interesting class of definite (single atom) consequences.