This monograph concentrates on the implementation of concurrent logic programming languages on loosely-coupled parallel computer architectures. Two different abstract models are also considered: a graph reduction based model and a more imperative approach. The design of a specialized instruction set is presented that is general enough to be used for the whole family of concurrent logic programming languages. In particular the language Parlog is concentrated upon because it is the most efficiently implementable of all the non-flat logic programming languages. Other issues arising from the implementation of a programming language are discussed, in particular the design of a load balancing scheme which deals with the large number of short-lived processes inherent in a correct language implementation. Detailed descriptions of all the data structures and synchronisation algorithms are also presented. Resource exhaustion is also discussed and handled within the implementations. Detailed performance results for both models of computation are given. From the material it should be possible for the reader to create an implementation.
PARLOG is a logic programming language designed for efficient implementation on parallel machines. It supports a declarative style of programming, combined with an execution mechanism that can exploit the parallel architectures which are already available. This book is a comprehensive study of the design, application, and implementation of PARLOG.
Parallel processing for AI problems is of great current interest because of its potential for alleviating the computational demands of AI procedures. The articles in this book consider parallel processing for problems in several areas of artificial intelligence: image processing, knowledge representation in semantic networks, production rules, mechanization of logic, constraint satisfaction, parsing of natural language, data filtering and data mining. The publication is divided into six sections. The first addresses parallel computing for processing and understanding images. The second discusses parallel processing for semantic networks, which are widely used means for representing knowledge - methods which enable efficient and flexible processing of semantic networks are expected to have high utility for building large-scale knowledge-based systems. The third section explores the automatic parallel execution of production systems, which are used extensively in building rule-based expert systems - systems containing large numbers of rules are slow to execute and can significantly benefit from automatic parallel execution. The exploitation of parallelism for the mechanization of logic is dealt with in the fourth section. While sequential control aspects pose problems for the parallelization of production systems, logic has a purely declarative interpretation which does not demand a particular evaluation strategy. In this area, therefore, very large search spaces provide significant potential for parallelism. In particular, this is true for automated theorem proving. The fifth section considers the problem of constraint satisfaction, which is a useful abstraction of a number of important problems in AI and other fields of computer science. It also discusses the technique of consistent labeling as a preprocessing step in the constraint satisfaction problem. Section VI consists of two articles, each on a different, important topic. The first discusses parallel formulation for the Tree Adjoining Grammar (TAG), which is a powerful formalism for describing natural languages. The second examines the suitability of a parallel programming paradigm called Linda, for solving problems in artificial intelligence. Each of the areas discussed in the book holds many open problems, but it is believed that parallel processing will form a key ingredient in achieving at least partial solutions. It is hoped that the contributions, sourced from experts around the world, will inspire readers to take on these challenging areas of inquiry.
The theme of this book is the potential of new advanced database systems. The volume presents the proceedings of the 10th British National Conference on Databases, held in Aberdeen, Scotland, in July 1992. The volume contains two invited papers, one on the promise of distributed computing andthe challenges of legacy systems by M.L. Brodie, and the other on object-oriented requirements capture and analysis and the Orca project by D.J.L. Gradwell. The following four parts each contain three submitted papers selected from a total of 36 submissions. The parts are entitled: - Object-oriented databases - Parallel implementationsand industrial systems - Non-relational data models - Logic programming and databases
P-Prolog is put forward as an alternative proposal to the difficulties faced in the main research areas of parallel logic programmings, which have been studied. P-Prolog provides the advantages of guarded Horn clauses while retaining don't know non-determinism where required. This monograph presents also an or-tree model and an implementation scheme for it, to combine and- and or- parallelism with reasonable efficiency. The model and implementation scheme discussed can be applied to P-Prolog and other parallel logic languages.
This volume contains papers presented at the second international workshop on extensions of logic programming, which was held at the Swedish Institute of Computer Science, Stockhom, January 27-29, 1991. The 12 papers describe and discuss several approaches to extensions of logic programming languages such as PROLOG, as well as connections between logic programming and functional programming, theoretical foundations of extensions, applications, and programming methodologies. The first workshop in this series was held in T}bingen in 1989 and its proceedings areavailable as LNCS 475. The third workshop will be held in Bologna in 1992.
