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Handout for G53KRR lecture on resolution . 1. Reducing a first order sentence to clausal normal form.
 

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