Prolog

Prolog is the most well-known and widely used logic programming language. Non-deterministic programming via backtracking is built in a sophisticated parser formalism known as Definite Clause Grammars (DCG) dcg. Constraint programming is frequently supported in modern variations. It is used for automated reasoning, deductive databases, planning and scheduling activities, natural language processing, web/business rule engines and is frequently used in schools to promote the declarative paradigm.