Rules for Backward Chaining

Backward chaining assumes rules of the form: A ∧ B → C Such a rule is called a Horn clause; a Horn clause has at most one positive literal when written in Conjunctive Normal Form as a disjunction (or) of literals: A ∧ B → C (A ∧ B) → C ¬ (A ∧ B) ∨ C ¬ A ∨ ¬ B ∨ C