Proof procedure and answer extraction in Petri net model of logic programs

A proof procedure and answer extraction in a high-level Petri net model of logic programs is discussed. The logic programs are restricted to the Horn clause subset of first-order predicate logic and finite problems. The logic program is modeled by a high-level Petri net and the execution of the logic program or the answer extraction process in predicate calculus corresponds to a firing sequence which fires the goal transition in the net. For the class of the programs described above, the goal transition is potentially firable if an only if there exists a nonnegative T-invariant which includes the goal transition in its support. This is the main result proved. Three examples are given to illustrate in detail the above results