15-815 Automated Theorem Proving
Lecture 11: Unification with Parameters
In this lecture we first prove the correctness of unification
as a sequence of transformations on unification formulas
with free variables.
We then consider the problems posed by the universal quantifier in
unification formulas. In order to preserve soundness we need to (1)
either record which parameters a unification variable is allowed to
depend on, or (2) replace universally quantified variables by so-called
Skolem constants. Both solutions have their difficulties.