The computer programming language Prolog is quickly gaining popularity throughout the world. Since Its beginnings around 1970. Prolog has been chosen by many programmers for applications of symbolic computation. including: D relational databases D mathematical logic D abstract problem solving D understanding natural language D architectural design D symbolic equation solving D biochemical structure analysis D many areas of artificial Intelligence Until now. there has been no textbook with the aim of teaching Prolog as a practical programming language. It Is perhaps a tribute to Prolog that so many people have been motivated to learn It by referring to the necessarily concise reference manuals. a few published papers. and by the orally transmitted 'folklore' of the modern computing community. However. as Prolog is beginning to be Introduced to large numbers of undergraduate and postgraduate students. many of our colleagues have expressed a great need for a tutorial guide to learning Prolog. We hope this little book will go some way towards meeting this need. Many newcomers to Prolog find that the task of writing a Prolog program Is not like specifying an algorithm in the same way as In a conventional programming language. Instead. the Prolog programmer asks more what formal relationships and objects occur In his problem.

The International Symposium on Practical Aspects of Declarative Languages (PADL) is a forum for researchers and practitioners to present original work emphasizing novel applications and implementation techniques for all forms of declarative concepts, especially those emerging from functional, logic, and c- straint languages. Declarative languages have been studied since the inception of computer science, and continue to be a vibrant subject of investigation today due to their applicability in current application domains such as bioinformatics, network con?guration, the Semantic Web, telecommunications software, etc. The 6th PADL Symposium was held in Dallas, Texas on June 18–19, 2004, and was co-located with the Compulog-Americas Summer School on Compu- tional Logic. From the submitted papers, the program committee selected 15 for presentation at the symposium based upon three written reviews for each paper, which were provided by the members of the program committee and additional referees. Two invited talks were presented at the conference. The ?rst was given by Paul Hudak (Yale University) on “An Algebraic Theory of Polymorphic T- poral Media. ” The second invited talk was given by Andrew Fall (Dowlland Technologies and Simon Fraser University) on “Supporting Decisions in C- plex, Uncertain Domains with Declarative Languages. ” Following the precedent set by the previous PADL symposium, the program committee this year again selected one paper to receive the ‘Most Practical - per’award.

This new edition of The Art of Prolog contains a number of important changes. Most background sections at the end of each chapter have been updated to take account of important recent research results, the references have been greatly expanded, and more advanced exercises have been added which have been used successfully in teaching the course. Part II, The Prolog Language, has been modified to be compatible with the new Prolog standard, and the chapter on program development has been significantly altered: the predicates defined have been moved to more appropriate chapters, the section on efficiency has been moved to the considerably expanded chapter on cuts and negation, and a new section has been added on stepwise enhancement—a systematic way of constructing Prolog programs developed by Leon Sterling. All but one of the chapters in Part III, Advanced Prolog Programming Techniques, have been substantially changed, with some major rearrangements. A new chapter on interpreters describes a rule language and interpreter for expert systems, which better illustrates how Prolog should be used to construct expert systems. The chapter on program transformation is completely new and the chapter on logic grammars adds new material for recognizing simple languages, showing how grammars apply to more computer science examples.

Written for those who wish to learn Prolog as a powerful software development tool, but do not necessarily have any background in logic or AI. Includes a full glossary of the technical terms and self-assessment exercises.