Clause Form

Any boolean formula can be put into conjunctive normal form (CNF). From there, it’s easy to get “clause form.” Automatic inference using resolution requires statements be in clause form.

If not Y then X and not Z.

Y or (X & not Z)

(Y or X & (Y or not Z)

(X V Y) & (Y V ~Z)

clauses: (X V Y), (Y V ~Z)

X, Y, and ~Z are called literals. (A literal is a variable or a negated variable.)

Each clause is a disjunction of literals.

A formula in CNF is a conjunction of clauses.

For our example with the butler, we get the following clause:

~ P V ~ Q V R

Previous slide

Next slide

Back to first slide

View graphic version