Chapter 2
Unification and Proof Search

This chapter has two main goals:

1. To discuss unification in Prolog, and to explain how Prolog unification differs from standard unification. Along the way, we’ll introduce =/2 , the built-in predicate for Prolog unification, and unify _with _occurs _check/2 , the built-in predicate for standard unification.
2. To explain the search strategy Prolog uses when it tries to deduce new information from old using modus ponens.