Efficient evaluation of a class of ordered logic programs

Abstract

Ordered Logic ( OL ) enhances logic programming by the capability of modeling complex knowledge, by permitting a natural representation of several forms of non-monotonic reasoning. Both well-founded and stable model semantics for OL programs can be found in the literature [7,20,22]. This paper focuses on the problem of the efficient evaluation of the well-founded semantics of OL programs. First, a class of OL programs, called quasi-stratified programs, is presented. Then, an algorithm for the efficient bottom-up evaluation of the well-founded model of quasi-stratified programs is provided. Quasi-stratified programs evaluation has been implemented in KIWIS, an advanced environment for large database systems, whose query language is based on OL.