The Representation and Deductive Retrieval of Complex Objects

The Relational Data Model and Relational Calculus are extended with Unification and non-recursive Horn Clauses from Logic. The benefits gained include better versatility and a richer functionality for expressing complex Jack, deductive queries and rule-based inJerences. Applications include semantic data models for Databases, frames for Knowledge-based systems, and Complex Objects for CAD. An Extended Relational Algebra (ERA) is introduced that has the same expressive power as the new Calculus. The algorithm given for translating Jrom Calculus to ERA supplies a sound basis for the compilation of these Horn clauses, and their implementation using query optimization and other techniques currently used in database systems.