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Graphs and colorings for answer set programming

Published online by Cambridge University Press:  27 January 2006

KATHRIN KONCZAK
Affiliation:
Institut für Informatik, Universität Potsdam, Postfach 90 03 27, D-14439 Potsdam, Germany (e-mail: konczak@cs.uni-potsdam.de, linke@cs.uni-potsdam.de, torsten@cs.uni-potsdam.de)
THOMAS LINKE
Affiliation:
Institut für Informatik, Universität Potsdam, Postfach 90 03 27, D-14439 Potsdam, Germany (e-mail: konczak@cs.uni-potsdam.de, linke@cs.uni-potsdam.de, torsten@cs.uni-potsdam.de)
TORSTEN SCHAUB
Affiliation:
Institut für Informatik, Universität Potsdam, Postfach 90 03 27, D-14439 Potsdam, Germany (e-mail: konczak@cs.uni-potsdam.de, linke@cs.uni-potsdam.de, torsten@cs.uni-potsdam.de)

Abstract

We investigate the usage of rule dependency graphs and their colorings for characterizing and computing answer sets of logic programs. This approach provides us with insights into the interplay between rules when inducing answer sets. We start with different characterizations of answer sets in terms of totally colored dependency graphs that differ in graph-theoretical aspects. We then develop a series of operational characterizations of answer sets in terms of operators on partial colorings. In analogy to the notion of a derivation in proof theory, our operational characterizations are expressed as (non-deterministically formed) sequences of colorings, turning an uncolored graph into a totally colored one. In this way, we obtain an operational framework in which different combinations of operators result in different formal properties. Among others, we identify the basic strategy employed by the noMoRe system and justify its algorithmic approach. Furthermore, we distinguish operations corresponding to Fitting's operator as well as to well-founded semantics.

Type
Regular Papers
Copyright
2006 Cambridge University Press

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