Everything in: Prolog (Programming Logic) Programming Language Overview
Prolog (Programming Logic) was created at the University of Marseille in the eary seventies by Alain Colmerauer, Robert Roussel and collegues. It is a declarative language mainly used for working with non-numerical objects. Prolog can be used alone or in complement with other traditional languages. Prolog is frequently used in Artificial Intelligence programming where manipulaton of symbols is a usual task. In Prolog implications are specified as logical predicates called Horn clauses, and it finds solutions by unification, which means binding a variable to a value.
Sources: An Introduction to Prolog by Loiseleur Michel and Vigier Nicolas, http://etud.epita.fr:8000/~vigier_n/Prolog/
Object-Oriented Language: Prolog, http://www.cetus-links.org/oo_prolog.html