Smodels ^A — A System for Computing Answer Sets of Logic Programs with Aggregates

Abstract

In [2], we presented a system called $\mathbb{ASP}$-$\mathbb{CLP}$ for computing answer sets of logic programs with aggregates. The implementation of $\mathbb{ASP}$-$\mathbb{CLP}$ relies on the use of an external constraint solver (ECLiPSe) to deal with aggregate literals and requires some modifications to the answer set solver used in the experiment (Smodels). In general, the system is capable of computing answer sets of arbitrary programs with aggregates, i.e., there is no syntactical restrictions imposed on the inputs to the system. This makes $\mathbb{ASP}$-$\mathbb{CLP}$ different from dlv ^A (built BEN/5/23/04) [1], which deals with stratified programs only. $\mathbb{ASP}$-$\mathbb{CLP}$, however, is based on a semantics that does not guarantee minimality of answer sets. Furthermore, our experiments with $\mathbb{ASP}$-$\mathbb{CLP}$ indicate that the cost of communication between the constraint solver and the answer set solver proves to be significant in large instances.