An Algorithm for Logically Deducing Horn Clauses and Processing Logic Queries

This paper shows that many production rules in a rule based system and some functional dependencies in a relational database can be transformed into Horn clauses. This paper also develops an algorithm for constructing a more general deduction graph that is extended from the algorithm in Ref. 12, originally designed for finding a subset of functional dependencies, which logically deduces a functional dependency not in the subset. Since a relational database is a special case of a logic program5, many existing techniques in the area of relational databases can be extended and then used in logic programming and particularly in the Horn clause logic queries without relying on the resolution-refutation theorem-proving method in artifical intelligence. By using this new graphical method, there are several advantages as compared with the standard PROLOG implementation.