An alternative semantic model for logic programming is that of Flat Concurrent Prolog. Compare Prolog as seen in Section 14.3 with Flat Concurrent Prolog (Shapiro 1987).

Use factoring and resolution to produce a refutation for the following clauses: p(X) ∨ p(f(Y)) and ¬ p(W) ∨ ¬ p(f(Z)). Try to produce a refutation without factoring.