Summary: Handout for G53KRR lecture on resolution .
1. Reducing a first order sentence to clausal normal form.
1. eliminate and using
( ) (¬ )
( ) (( ) ( ))
2. move ¬ inward so that it appears only in front of an atom, using
¬¬
¬( ) (¬ ¬)
¬( ) (¬ ¬)
¬x x¬
¬x x¬
3. ensure that each quantifier has a distinct variable by renaming:
x y(x/y)
x y(x/y)
where y does not occur in x and x and (x/y) means with all
occurrences of x replaced by y.
4. eliminate existentials using Skolemisation:
if x is not in the scope of any universal quantifiers, then we replace
x with (a) where a is a new constant called a Skolem constant.
(It should be different for every existential quantifier).

Source: Alechina, Natasha - School of Computer Science, University of Nottingham

Collections: Computer Technologies and Information Sciences