BDDs, Horn Clauses and Resolution

In this research we present the utilization of BDDs in representing propositional logic programs and implementing the refutation by resolution deduction method. A logic program is a collection of axioms from which a goal clause can be proven. Axioms are written in a standard form known as Horn clauses. In logic programming, we try to find a collection of axioms and inference steps that imply the goal. The standard and usual method for this kind of inference is ‘refutation by resolution’. Binary Decision Diagrams, shortly called BDDs, are data structures proposed for representing switching functions. BDDs have been found more practical and more efficient in time and space than other switching function representation methods. One may consider a Horn clause as a switching function and represent it as a BDD. In the same way, all the clauses of a propositional logic program and the goal clause can be represented by means of a multi-rooted BDD. Because of the characteristics of BDDs we can make the inference in some other methods in addition to the standard method. In this paper, this kind of representation as well as proving the goal in formal linear resolution and Non-linear resolution are investigated.