Conflicts in Generalised Modular Logic Programming

Modularity has been studied extensively in conventional logic programming and incorporating modularity into Answer Set Programming has also become popular in the last few years. A major approach is Oikarinnen and JanhunenÕs Gaifman-Shapiro-style architecture of program modules, which provides the composition of program modules. Recently one shortcoming to their approach, imposed in order to ensure the compatibility of their module system with the stable model semantics and that forcing output signatures of composing modules to be disjoint, has been lifted [14]. However, lifting such requirements implies that conflicts will occur in composed modules mostly because their design is errorprone and also due to the lack of automated conflict detection and resolution. We describe an improved modularity definition for logic programs, identify its basic conflict types and characterize these conflicts both in terms of Strong and Uniform Equivalence of logic programs and in terms of a novel Brave Equivalence. The conflicts are studied according to several dimensions, and a hierarchy of conflict types is proved to exist. These theoretical characterizations allow for the automatic identification of such conflicts, among other reasoning tasks.