Concepts An occurrence of a quantifier Vc or d.c is vacuous if its variable has no free occurrence n its scope i i occurs positively/negatively in a iff EiiC is a positive/negative wf part of A Logic in Computer Science-p. 3/9Concepts • An occurrence of a quantifier ∀x or ∃x is vacuous if its variable x has no free occurrence in its scope. • ∃∀ixi occurs positively /negatively in A iff ∃∀ixiC is a positive /negative wf part of A. Logic in Computer Science – p.3/9