Computing Prioritized Circumscription via Compilation into Logic Programs

Abstract

Recently, Gelfond and Lifschitz proposed an efficient computational method for prioritized circumscription which compiles circumscriptive theories into logic programs. But there are such difficulties in their method that a given circumscriptive theory cannot always be compiled successfully due to strong assumption about the syntax of a circumscriptive theory. So, we extend their method in order to expand its applicable class while keeping its computational efficiency. Our idea is to transform a given circumscription into a logically equivalent one in which such difficulties disappear. In this paper, we show it can be done by making use of Lifschitz's result that some parallel circumscription can be replaced by an equivalent first-order theory. As a result, some class of prioritized circumscription, which cannot be handled by Gelfond and Lifschitz"s method, can be compiled into logic programs by our method.