In: IEICE Trans. on Fundamentals of Electronics, Communications, and Computer Science, Vol. E74-A, No. 10, pages 1579-1587. 1994.
Abstract: Nonmonotonic reasoning is a logical inference system which attempts to approximate human common sense reasoning and is characterized as unfeasible: having reasonably drawn a conclusion from some premises we may be forced to retract that conclusion upon learning new facts. This paper introduces a Petri net model for nonmonotonic reasoning with nonmonotonic rules generated by annotated logic programs and the unless operator. In the Petri net model, a fixpoint of a nonmonotonic theory can be represented as a maximal and consistent support of a firing sequence. We propose a structural method for finding extensions (coherent consequences) for a given set of nonmonotonic logic rules. It is based on the T-invariant technique for testing fireability of a goal transition in the Petri net model of Horn clause logic programs.
Keywords: Petri nets, T-invariants, annotated logic programs, nonmonotonic reasoning.