The fourth edition of this best-selling guide to Prolog & Artificial Intelligence has been updated to include key developments in the field while retaining its lucid approach to these topics. New & extended topics include Constraint Logic Programming abductive reasoning & partial order planning. Divided into two parts the first part of the book introduces the programming language Prolog while the second part teaches Artificial Intelligence using Prolog as a tool for the implementation of AI techniques. This textbook is meant to teach Prolog as a practical programming tool & so it concentrates on the art of using the basic mechanisms of Prolog to solve interesting problems. The fourth edition has been fully revised & extended to provide an even greater range of applications making it a self-contained guide to Prolog AI or AI Programming for students & professional programmers.