We introduce unfounded sets and well-founded partial models, and define the well-founded semantics of a program to be its well-founded partial model. If the well-founded partial model is in fact a total model, we call it the well-founded model. We show that the class of programs possessing a total well-founded model properly includes previously studied classes of 'stratified' and 'locally stratified' programs. We also compare our method with other proposals in the literature, including Clark's 'program completion, ' Fitting's and Kunen's 3-valued interpretations of it, and the 'stable models' of Gelfond and Lifschitz."

The emergence of new paradigms for data management raises a variety of exciting challenges. An important goal of database theory is to answer these challenges by providing sound foundations for the development of the field. This volume contains the papers selected for the third International Conference on Database Theory, ICDT'90. The conferences in this series are held biannually in beautiful European cities, Rome in 1986 and Bruges in 1988 with proceedings published as volumes 234 and 326 in the same series. ICDT'90 was organized in Paris by the Institut National de Recherche en Informatique et Automatique. The conference features 2 invited presentations and 31 papers selected from 129 submissions. The papers describe original ideas and new results on the foundations of databases, knowledge bases, object-oriented databases, relational theory, transaction management, data structures and deductive databases. The volume offers a good overview of the state of the art and the current trends in database theory. It should be a valuable source of information for researchers interested in the field.

Students explore the idea that thinking is a form of computation by learning to write simple computer programs for tasks that require thought. This book guides students through an exploration of the idea that thinking might be understood as a form of computation. Students make the connection between thinking and computing by learning to write computer programs for a variety of tasks that require thought, including solving puzzles, understanding natural language, recognizing objects in visual scenes, planning courses of action, and playing strategic games. The material is presented with minimal technicalities and is accessible to undergraduate students with no specialized knowledge or technical background beyond high school mathematics. Students use Prolog (without having to learn algorithms: “Prolog without tears!”), learning to express what they need as a Prolog program and letting Prolog search for answers. After an introduction to the basic concepts, Thinking as Computation offers three chapters on Prolog, covering back-chaining, programs and queries, and how to write the sorts of Prolog programs used in the book. The book follows this with case studies of tasks that appear to require thought, then looks beyond Prolog to consider learning, explaining, and propositional reasoning. Most of the chapters conclude with short bibliographic notes and exercises. The book is based on a popular course at the University of Toronto and can be used in a variety of classroom contexts, by students ranging from first-year liberal arts undergraduates to more technically advanced computer science students.

This book constitutes the refereed proceedings of the 21st International Conference on Logic and Programming, ICLP 2005, held in Barcelona, Spain, in October 2005. The 25 revised full papers and 15 revised poster papers presented together with 4 invited papers and 7 abstracts of a poster session of a doctoral consortium were carefully reviewed and selected from 104 submissions. The papers cover all issues of current research in logic programming. Extra attention is given to novel applications of logic programming and work providing novel integrations of different areas.

Includes tutorials, lectures, and refereed papers on all aspects of logic programming, including theoretical foundations, constraints, concurrency and parallelism, deductive databases, language design and implementation, nonmonotonic reasoning, and logic programming and the Internet. The International Conference on Logic Programming, sponsored by the Association for Logic Programming, includes tutorials, lectures, and refereed papers on all aspects of logic programming, including theoretical foundations, constraints, concurrency and parallelism, deductive databases, language design and implementation, nonmonotonic reasoning, and logic programming and the Internet.

This book gives an account oC the mathematical Coundations oC logic programming. I have attempted to make the book selC-contained by including prooCs of almost all the results needed. The only prerequisites are some Camiliarity with a logic programming language, such as PROLOG, and a certain mathematical maturity. For example, the reader should be Camiliar with induction arguments and be comCortable manipulating logical expressions. Also the last chapter assumes some acquaintance with the elementary aspects of metric spaces, especially properties oC continuous mappings and compact spaces. Chapter 1 presents the declarative aspects of logic programming. This chapter contains the basic material Crom first order logic and fixpoint theory which will be required. The main concepts discussed here are those oC a logic program, model, correct answer substitution and fixpoint. Also the unification algorithm is discussed in some detail. Chapter 2 is concerned with the procedural semantics oC logic programs. The declarative concepts are implemented by means oC a specialized Corm oC resolution, called SLD-resolution. The main results of this chapter concern the soundness and completeness oC SLD-resolution and the independence oC the computation rule. We also discuss the implications of omitting the occur check from PROLOG implementations. Chapter 3 discusses negation. Current PROLOG systems implement a form of negation by means of the negation as failure rule. The main results of this chapter are the soundness and completeness oC the negation as failure rule.