T. Eiter, M. Fink, T. Krennwallner, C. Redl, P. Schüller:
"Exploiting Unfounded Sets for HEX-Program Evaluation";
Talk: 13th European Conference on Logics in Artificial Intelligence (JELIA 2012), Toulouse, France; 2012-09-26 - 2012-09-28; in: "13th European Conference on Logics in Artificial Intelligence (JELIA 2012)", L. del Cerro, A. Herzig, J. Mengin (ed.); Springer, LNCS 7519 (2012), ISBN: 978-3-642-33352-1; 160 - 175.

HEX programs extend logic programs with external computations through external atoms, whose answer sets are the minimal models of the Faber-Leone-Pfeifer-reduct. As already reasoning from Horn programs with nonmonotonic external atoms of polynomial complexity is on the second level of the polynomial hierarchy, answer set checking needs special attention; simply computing reducts and searching for smaller models does not scale well. We thus extend an approach based on unfounded sets to HEX and integrate it in a Conflict Driven Clause Learning framework for HEX program evaluation. It reduces the check to a search for unfounded sets, which is more efficiently implemented as a SAT problem. We give a basic encoding for HEX and show optimizations by additional clauses. Experiments show that the new approach significantly decreases runtime.

Answer Set Programming, Nonmonotonic Reasoning, Unfounded Sets, FLP Semantics

http://dx.doi.org/10.1007/978-3-642-33353-8_13

Project Head Thomas Eiter:
Evaluierung von ASP Programming mit Externen Zugriffen

Project Head Thomas Eiter:
Modulare HEX-Programme

Project Head Thomas Eiter:
Schließen in hybriden Wissensbasen

Project Head Michael Fink:
Inconsistency Management for Knowledge-Integration Systems