The Resolution Principle is a rule of inference for Relational Logic analogous to the Propositional Resolution Principle for Propositional Logic. Using the Resolution Principle alone (without axiom schemata or other rules of inference), it is possible to build a reasoning program that is sound and complete for all of Relational Logic. The search space using the Resolution Principle is smaller than the search space for generating Herbrand proofs.
In our tour of resolution, we look first at unification, which allows us to unify expressions by substituting terms for variables. We then move on to a definition of clausal form extended to handle variables. The Resolution Principle follows. We then look at some applications. Finally, we examine strategies for making the procedure more efficient.