Publications in Scientific Journals:
T. Eiter, M. Fink, T. Krennwallner, C. Redl, P. Schüller:
"Efficient HEX-Program Evaluation based on Unfounded Sets";
Journal of Artificial Intelligence Research,
HEX-programs extend logic programs under the answer set semantics with external computations through external atoms. As reasoning from ground Horn programs with nonmonotonic external atoms of polynomial complexity is already on the second level of the polynomial hierarchy, minimality checking of answer set candidates needs special attention. To this end, we present an approach based on unfounded sets as a generalization of related techniques for ASP programs. The unfounded set detection is expressed as a propositional SAT problem, for which we provide two different encodings and optimizations to them. We then integrate our approach into a previously developed evaluation framework for HEX-programs, which is enriched by additional learning techniques that aim at avoiding the reconstruction of the same or related unfounded sets. Furthermore, we provide a syntactic criterion that allows one to skip the minimality check in many cases. An experimental evaluation shows that the new approach significantly decreases runtime.
Answer Set Programming, Nonmonotonic Reasoning, External Source Access
"Official" electronic version of the publication (accessed through its Digital Object Identifier - DOI)
Electronic version of the publication:
Project Head Thomas Eiter:
Evaluierung von ASP Programming mit Externen Zugriffen
Created from the Publication Database of the Vienna University of Technology.