Information systems are large repositories of factual and inferential knowledge intended to be queried and maintained by a wide variety of users with different backgrounds and work tasks. The community of potential information system users is growing rapidly with advances in hardware and software technology that permit computer/communications support for more and more application areas. Unfortunately, it is often felt that progress in user interface technology has not quite matched that of other areas. Technical solutions such as computer graphics, natural language processing, or man-machine-man communications in office systems are not enough by themselves. They should be complemented by system features that ensure cooperative behavior of the interfaces, thus reducing the training and usage effort required for successful interaction. In analogy to a human dialog partner, we call an interface cooperative if it does not just accept user requests passively or answer them literally, but actively attempts to understand the users' intentions and to help them solve their applica tion problems. This leads to the central question addressed by this book: What makes an information systems interface cooperative, and how do we provide capabilities leading to cooperative interfaces? Many answers are possible. A first aspect concerns the formulation and accep tance of user requests. Many researchers assume that such requests should be formulated in natural language.

Alan Robinson This set of essays pays tribute to Bob Kowalski on his 60th birthday, an anniversary which gives his friends and colleagues an excuse to celebrate his career as an original thinker, a charismatic communicator, and a forceful intellectual leader. The logic programming community hereby and herein conveys its respect and thanks to him for his pivotal role in creating and fostering the conceptual paradigm which is its raison d’Œtre. The diversity of interests covered here reflects the variety of Bob’s concerns. Read on. It is an intellectual feast. Before you begin, permit me to send him a brief personal, but public, message: Bob, how right you were, and how wrong I was. I should explain. When Bob arrived in Edinburgh in 1967 resolution was as yet fairly new, having taken several years to become at all widely known. Research groups to investigate various aspects of resolution sprang up at several institutions, the one organized by Bernard Meltzer at Edinburgh University being among the first. For the half-dozen years that Bob was a leading member of Bernard’s group, I was a frequent visitor to it, and I saw a lot of him. We had many discussions about logic, computation, and language.

Logic Programming was effectively defined as a discipline in the early seventies. It is only during the early to mid eighties that books, conferences and journals devoted entirely to Logic Programming began to appear. Consequently, much of the work done during this first crucial decade in Marseilles, Edinburgh, London, Budapest and Stockholm (to name a few) is often overlooked or difficult to trace. There are now two main regular conferences on Logic Programming, and at least five journals: The Journal of Logic Programming, New Generation Computing, Automated Reasoning, The Journal of SJmbolic Computation, and Future Generation Computer Systems. Logic Programming, however, has its roots in Automated Theorem Proving and via the expanding area of expert systems, strongly influences researchers in such varied fields as Civil Engineering, Chemistry, Law, etc. Consequently, many papers related to Logic Programming appear in a wide variety of journals and proceedings of conferences in other disciplines. This is particularly true of Computer Science where a revolution is taking place in hardware design, programming languages, and more recently databases. One cannot overestimate the importance of such a bibliography.