High-level Petri net model of logic program with negation

Abstract

The formalism of nonmonotonic reasoning has been integrated into logic programming to define semantics for logic program with negation. Because a Petri net provides a uniform model for both the logic of knowledge and the control of inference, the class of high-level Petri nets called predicate/transition nets (PrT-nets) has been employed to study production rule based expert systems and Horn clause logic programs. We show that a PrT-net can implement the nonmonotonicity associated with a logic program with negation as well as the monotonicity of Horn clause logic program. In particular, we define a semantics for a normal logic program and implement it with PrT-net. We demonstrate that in the presence of inconsistency in a normal logic program, the semantics still works well by deducing meaningful answers. The variations and potential applications of the PrT-net are also addressed. >