Coordinating production across a supply chain, designing a new VLSI chip, allocating classrooms or scheduling maintenance crews at an airport are just a few examples of complex (combinatorial) problems that can be modeled as a set of decision variables whose values are subject to a set of constraints. The decision variables may be the time when production of a particular lot will start or the plane that a maintenance crew will be working on at a given time. Constraints may range from the number of students you can 't in a given classroom to the time it takes to transfer a lot from one plant to another.Despiteadvancesincomputingpower, manyformsoftheseandother combinatorial problems have continued to defy conventional programming approaches. Constraint Logic Programming (CLP) ?rst emerged in the mid-eighties as a programming technique with the potential of signi?cantly reducing the time it takes to develop practical solutions to many of these problems, by combining the expressiveness of languages such as Prolog with the compu- tional power of constrained search. While the roots of CLP can be traced to Monash University in Australia, it is without any doubt in Europe that this new software technology has gained the most prominence, bene?ting, among other things, from sustained funding from both industry and public R&D programs over the past dozen years. These investments have already paid o?, resulting in a number of popular commercial solutions as well as the creation of several successful European startups.

From the viewpoint of an "industrial" this book is most welcome, as one of the most significant demonstrations of the maturity of Prolog. Logic programming is a fascinating area in computer science, which held for years - and still does - the promise of freeing ourselves from programming based on the "Von Neumann" machine. In addition computer programming has long been for solid theoretical foundations. While conventional engineering, dealing mainly with "analogical complexity," developed over some hundred years a complete body of mathematical tools, no such toolset was available for "digital complexity." The only mathematical discipline which deals with digital complexity is logic and Prolog is certainly the operational tool which comes closest to the logical programming ideal. So, why does Prolog, despite nearly twenty years of development, still appear to many today to be more of a research or academic tool, rather than an industrial programming language? A few reasons may explain this: First, I think Prolog suffers from having been largely assimilated into - and thus followed the fate of - Artificial Intelligence. Much hype in the late 1980 created overexpectations and failed to deliver, and the counterreaction threw both AI and Prolog into relative obscurity. In a way, maybe this is a new chance for the Prolog community: the ability to carry out real work and progress without the disturbance of limelights and the unrealistic claims of various gurus. Second, programming in Prolog is a new experience for computer professionals.

Attribute grammars were introduced over twenty years ago, but they are still not as widely used as could have been hoped initially. This is particularly so in industry, despite their qualities as a specification tool. The aim of this International Workshop on Attribute Grammars and their Applications (WAGA), the first to be entirely devoted to this topic, was to show that they are still the subject of active research and now lead to important, useful and practical applications in various areas. The workshop covered all aspects of attribute grammars, with an emphasis on practical results. This volume includes the text of the three invited talks and 21 submitted papers presented at the workshop. This selection provides a wide view of the diverse research being done in the area. Topics include: - Fundamentals: efficient exhaustive and incremental at- tribute evaluation methods, parallel evaluation, space optimization, relationships with functional, logic and object-oriented programming, and systems. - Applications: compiler construction, natural language processing, and interactive program manipulation.

This volume consists of the papers accepted for presentation at the second international workshop on Programming Language Implementation and Logic Programming (PLILP '90) held in LinkAping, Sweden, August 20-22, 1990. The aim of the workshop was to identify concepts and techniques used both in implementation of programming languages, regardless of the underlying programming paradigm, and in logic programming. The intention was to bring together researchers working in these fields. The volume includes 26 selected papers falling into two categories. Papers in the first category present certain ideas from the point of view of a particular class of programming languages, or even a particular language. The ideas presented seem to be applicable in other classes of languages. Papers in the second category directly address the problem of integration of various programming paradigms. The proceedings of the predecessor workshop PLILP '88, held in OrlA(c)ans, France, May 16-18, 1988, are available as Lecture Notes in Computer Science, Vol. 348.

The aim of the workshop was to discuss whether research on implementation of programming languages and research on logic programming can mutually benefit from each others results. The intention was to bring together researchers from both fields, especially those working in the area of their intersection. Problems such as formal specification of compilers and syntax-based editors, program analysis and program optimization have been traditionally studied by implementors of algorithmic languages and have resulted in a number of well-established notions, formalisms and techniques. At the same time, an increasing number of people use logic programming as a way of specifying compilers or other programming environment tools, taking advantage of the relatively high level of logic programming and the growing efficiency of Prolog implementations. On the other hand, research on logic programming raises the questions of analysis of logic programs and their optimization. These are motivated primarily by compiler construction for logic programs, by studies on the methodology of logic programming and by the attempts to amalgamate logic programming and functional programming. The purpose of the workshop is to review the techniques developed in one (or both) of the fields which could also be of some help in the other one and to facilitate the transfer of expertise. It seems important to compare notions used in both fields: showing similarities between them may prevent rediscovering results already known, while studying differences may contribute to the transfer of technology.

Attribute Grammars have turned into one of the most fundamental formalisms of modern Computer Science. Since 1968 when Knuth introduced the basic concepts, they have been the subject of a very large amount of literature, proving the importance of the area and the broad range of its applications. The aim of the book is to put at the disposal of researchers and students, but also of engineers interested in applications, the most important definitions and results known to date in this youthful domain. This seemed best achieved by a survey including three parts: 1) A state-of-the-art review of the main results and of the most promising research directions: this part aims at being both an aid for the reader in understanding the bibliography, by presenting the results using a unified vocabulary together with numerous pointers to the literature, and also an incitement to go into further results and research areas. 2) A presentation of most of the systems dealing with Attribute Grammars: the main interest in this part lays in the presentation of the implementation choices and of the applications. This part is the "practical" side of the book, emphasizing the point of view of "design" which can outline the differences between a theoretical idea and the way it can be implemented. 3) A bibliography including about 600 titles on the domain, together with a thematic index enabling readers to find their way easily in accordance with their own points of interest.