Preprocessing of Complex Non-Ground Rules in Answer Set Programming

In this paper we present a novel method for preprocessing complex non-ground rules in answer set programming (ASP). Using a well-known result from the area of conjunctive query evaluation, we apply hypertree decomposition to ASP rules in order to make the structure of rules more explicit to grounders. In particular, the decomposition of rules reduces the number of variables per rule, while on the other hand, additional predicates are required to link the decomposed rules together. As we show in this paper, this technique can reduce the size of the grounding significantly and thus improves the performance of ASP systems in certain cases. Using a prototype implementation and the benchmark suites of the Answer Set Programming Competition 2011, we perform extensive tests of our decomposition approach that clearly show the improvements in grounding time and size.

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