Programming in Logic developed in 1970, France and declarative language.

Prolog is a combination of the following key ideas:
– if- then rules with variables
– Relational databases (w/ terms for data structuring)
– Backward Chaining to try to prove goals
– Unification to match goals to rule conclusions.
– Backtracking to try all possibilities

PROLOG works with facts, relations and rules.

A fact is a unit of information which is assumed to be true.

A relation combines two or more facts.

A rule is a conditional assertion of a fact.