Since its conception nearly 20 years ago, logic programming has been developed to the point where it now plays an important role in areas such as database theory, artificial intelligence and software engineering. There are, however, still many outstanding research issues which need to be addressed, and the UK branch of the Association for Logic Programming was set up to provide a forum where the flourishing research community could discuss important issues which were often by- passed at the larger international conferences. This volume contains the invited papers, refereed papers and tutorials presented at the 4th ALPUK Conference, which aimed to broaden the frontiers of logic programming by encouraging interaction between it and other related disciplines. The papers cover a variety of technical areas, including concurrent logic languages and their semantics, applications of logic languages to other (non-classical) logical systems, modules, types and error-handling, and the distributed execution of Prolog programs. The wide scope of the papers refelects the breadth of interest in this important area of computer science. ALPUK 92 provides a comprehensive overview of current progress being made in logic programming research. It will be of interest to all workers in the field, especially researchers, postgraduate students, and research and development workers in industry.

The goal of the AMAST conferences is to foster algebraic methodology as a foundation for software technology, and to show that this can lead to practical mathematical alternatives to the ad-hoc approaches commonly used in software engineering and development. The first two AMAST conferences, held in May 1989 and May 1991 at the University of Iowa, were well received and encouraged the regular organization of further AMAST conferences on a biennial schedule. The third Conference on Algebraic Methodology and Software Technology was held in the campus of the University of Twente, The Netherlands, during the first week of Summer 1993. Nearly a hundred people from all continents attended the conference. The largest interest received by the AMAST conference among the professionals extended to include the administration organizations as well. AMAST'93 was opened by the Rector of the University of Twente, followed by the Local Chairman. Their opening addresses open this proceedings, too. The proceedings contains 8 invited papers and 32 selected communica tions. The selection was very strict, for 121 submissions were received.

The Functional Programming Group at the University of Glasgow was started in 1986 by John Hughes and Mary Sheeran. Since then it has grown in size and strength, becoming one of the largest computing science research groups at Glasgow and earning an international reputation. The first Glasgow Functional Programming Workshop was organised in the summer of 1988. Its purpose was threefold: to provide a snapshot of all the research going on within the group, to share research ideas between Glaswegians and colleagues in the U.K. and abroad, and to introduce research students to the art of writing and presenting papers at a semi-formal (but still local and friendly) conference. The success of the first workshop has led to an annual series: Rothesay (1988), Fraserburgh (1989), Ullapool (1990). Portree (1991), Ayr (1992), and the workshop reported in these proceedings: Ayr (1993). Most participants wrote a paper that appeared in the draft proceedings (distributed at the workshop), and each draft paper was presented by one of the authors. The papers were all refereed by several other participants at the workshop, both internal and external, and the programme committee selected papers for these proceedings. Most papers have been revised twice, based firstly on feedback at the workshop, and secondly using the referee reports.

The Glasgow Functional Programming Group is widely recognised for its research in lazy functional languages. Once again this year, for the fifth time, we retreated to a Scottish seaside town to discuss our latest work, this time spending three days in Ayr. We were joined by a number of colleagues from other universities and from industry, with whom we have been enjoying fruitful collaboration. The workshop serves the dual purpose of ensuring that the whole group remains informed of each other's work, and of providing workshop experience for research students. Most participants presented a short talk about their work, supplemented by papers which appeared in a draft proceedings distributed at the workshop. Since then the papers have been reviewed and the majority are now published here following revision. The workshop also contained a lively discussion session on functional language applications, to which the industrial participants made very helpful contributions. One interesting feature of this volume is the number of papers addressing practical issues of realistic use of functional languages, from benchmarking and profiling, to user interfaces and file handling. It is perhaps indicative that at last lazy functional languages are being used for significantly larger applications than has been typical in the past. This type of paper is likely to feature prominently in relevant conference proceedings for the next few years. Other papers here continue to address more theoretical topics, such as program logic, semantics of non determinism, program analysis, and loop detection.

We hope that all readers will find the papers included in this volume of interest. All were presented at the 14th BCS IRSG Research Colloquium held at Lancaster University on 13th-14th April 1992. The papers display very well the scope and breadth of information retrieval, as indeed did the workshop ilself. They also present a good cross-section of current IR research, and as such provide a useful signpost for trends in information retrieval. Before we finish we must thank the following colleagues: Simon Botley, Paul Rayson and Paul Jones for their help in the organization of the conference. We would also like to extend a special message of thanks to Professor G.N. Leech of the Department of Linguistics at Lancaster and Roger Garside of the Department of Computing at Lancaster for their support during the conference period. Tony McEnery would also like to express his thanks and gratitude to Paul Baker for his help during the production of this book. September 1992 Tony McEnery Chris Paice Contents A Logical Model of Information Retrieval Based on Situation Theory M. La/mas and K. van Rijsbergen ........................................................ .

This is the proceedings of the seventh annual workshop held by the Glasgow Functional Programming Group. The purpose of the workshop is to provide a focus for new research, to foster research contacts with other functional language researchers, and to provide a platform for research students to develop their presentation skills. As in previous years, we spent three days closeted together in a pleasant seaside town, isolated from normal work commitments. We were joined by colleagues from other universities (both UK and abroad) and from industry. Workshop participants presented a short talk about their current research work, and produced a paper which appeared in a draft proceedings. These papers were then reviewed and revised in the light of discussions at the workshop and the referees' comments. A selection of those revised papers (the majority of those presented at the workshop) appears here in the published proceedings. The papers themselves cover a wide span, from theoretical work on algebras and bisimilarity to experience with a real-world medical applica tion. Unsurprisingly, given Glasgow's track record, there is a strong emphasis on compilation techniques and optimisations, and there are also several papers on concurrency and parallelism.

The Sixth International Workshop on Persistent Object Systems was held at Les Mazets des Roches near Tarascon, Provence in southern France from the fifth to the ninth of September 1994. The attractive context and autumn warmth greeted the 53 participants from 12 countries spread over five continents. Persistent object systems continue to grow in importance. Almost all significant uses of computers to support human endeavours depend on long-lived and large-scale systems. As expectations and ambitions rise so the sophistication of the systems we attempt to build also rises. The quality and integrity of the systems and their feasibility for supporting large groups of co-operating people depends on their technical founda tion. Persistent object systems are being developed which provide a more robust and yet simpler foundation for these persistent applications. The workshop followed the tradition of the previous workshops in the series, focusing on the design, implementation and use of persistent object systems in particular and persistent systems in general. There were clear signs that this line of research is maturing, as engineering issues were discussed with the aid of evidence from operational systems. The work presented covered the complete range of database facilities: transactions, concurrency, distribution, integrity and schema modifica tion. There were examples of very large scale use, one involving tens of terabytes of data. Language issues, particularly the provision of reflection, continued to be important.

This book is the proceedings of a workshop held at Heriot-Watt University in Edinburgh in August 1993. The central theme of the workshop was rules in database systems, and the papers presented covered a range of different aspects of database rule systems. These aspects are reflected in the sessions of the workshop, which are the same as the sections in this proceedings: Active Databases Architectures Incorporating Temporal Rules Rules and Transactions Analysis and Debugging of Active Rules Integrating Graphs/Objects with Deduction Integrating Deductive and Active Rules Integrity Constraints Deductive Databases The incorporation of rules into database systems is an important area of research, as it is a major component in the integration of behavioural information with the structural data with which commercial databases have traditionally been associated. This integration of the behavioural aspects of an application with the data to which it applies in database systems leads to more straightforward application development and more efficient processing of data. Many novel applications seem to need database systems in which structural and behavioural information are fully integrated. Rules are only one means of expressing behavioural information, but it is clear that different types of rule can be used to capture directly different properties of an application which are cumbersome to support using conventional database architectures. In recent years there has been a surge of research activity focusing upon active database systems, and this volume opens with a collection of papers devoted specifically to this topic.

The papers in this volume were presented at the First International Workshop on Larch, held at MIT Endicott House near Boston on 13-15 July 1992. Larch is a family of formal specification languages and tools, and this workshop was a forum for those who have designed the Larch languages, built tool support for them, particularly the Larch Prover, and used them to specify and reason about software and hardware systems. The Larch Project started in 1980, led by John Guttag at MIT and James Horning, then at Xerox/Palo Alto Research Center and now at Digital Equipment Corporation/Systems Research Center (DEC/SRC). Major applications have included VLSI circuit synthesis, medical device communications, compiler development and concurrent systems based on Lamport's TLA, as well as several applications to classical theorem proving and algebraic specification. Larch supports a two-tiered approach to specifying software and hardware modules. One tier of a specification is wrillen in the Larch Shared Language (LSL). An LSL specification describes mathematical abstractions such as sets, relations, and algebras; its semantics is defined in terms of first-order theories. The second tier is written in a Larch interface language, one designed for a specific programming language. An interface specification describes the effects of individual modules, e.g. state changes, resource allocation, and exceptions; its semantics is defined in terms of first-order predicates over two states, where state is defined in terms of the programming language's notion of state. Thus, LSL is programming language independent; a Larch interface language is programming language dependent.