The main idea behind the series of volumes Advances in Petri Nets is to present to the general computer science community recent results which are the most representative and significant for the development of the area. Thepapers for the volumes are drawn mainly from the annual International Conferences on Applications and Theory of Petri Nets. Selected papers from the latest conference are independently refereed, and revised and extended as necessary. Some further papers submitted directly to the editor are included. Advances in Petri Nets 1991 covers the 11th International Conference on Applications and Theory of Petri Nets held in Paris, France in June 1991. The volume contains the Bibliography of Petri Nets 1990 prepared by H. Pl}nnecke and W. Reisig, with over 4000 entries.

The main idea behind the series of volumes Advances in Petri Nets is to present to the general computer science community recent results which are the most representative and significant for the development of the area. The papers for the volumes are drawn mainly from the annual International Conferences on Applications and Theory of Petri Nets. Selected papers from the latest conference are independently refereed, and revised and extended as necessary. Some further papers submitted directly to the editor are included. Advances in Petri Nets 1990 covers the Tenth International Conference on Applications and Theory of Petri Nets held in Bonn, Germany, in June 1989. Additional highlights of this volume include a tutorial on refinements of Petri nets by W. Brauer, R. Gold, and W. Vogler, and a tutorial on analysis and synthesis of free choice systems by J. Esparza and M. Silva, both prepared in the framework of the ESPRIT Basic Research Actions Project DEMON.

High-level Petri nets are now widely used in both theoretical analysis and practical modelling of concurrent systems. The main reason for the success of this class of net models is that they make it possible to obtain much more succinct and manageable de scriptions than can be obtained by means of low-level Petri nets-while, on the other hand, they still offer a wide range of analysis methods and tools. The step from low-level nets to high-level nets can be compared to the step from assembly languages to modem programming languages with an elaborated type concept. In low-level nets there is only one kind of token and this means that the state of a place is described by an integer (and in many cases even by a boolean value). In high-level nets each token can carry complex information which, e. g. , may describe the entire state of a process or a data base. Today most practical applications of Petri nets use one of the different kinds of high-level nets. A considerable body of knowledge exists about high-level Petri nets this includes theoretical foundations, analysis methods and many applications. Unfortunately, the papers on high-level Petri nets have been scattered throughout various journals and collections. As a result, much of this knowledge is not readily available to people who may be interested in using high-level nets.

This work relates different approaches for the modelling of parallel processes. On the one hand there are the so-called "process algebras" or "abstract programming languages" with Milner's Calculus of Communicating Systems (CCS) and the theoretical version of Hoare's Communicating Sequential Processes (CSP) as main representatives. On the other hand there are machine models, i.e. the classical finite state automata (transition systems), for which, however, more discriminating notions of equivalence than equality of languages are used; and secondly, there are differently powerful types of Petri nets, namely safe and general (place/transition) nets respectively, and predicate/transition nets. Within a uniform framework the syntax and the operational semantics of CCS and TCSP are explained. We consider both, Milner's well-known interleaving semantics, which is based on infinite transition systems, as well as the new distributed semantics introduced by Degano et al., which is based on infinite safe nets. The main part of this work contains three syntax-driven constructions of transition systems, safe nets, and predicate/transition nets respectively. Each of them is accompanied by a proof of consistency. Due to intrinsic limits, which are also investigated here, neither for transition systems and finite nets, nor for general nets does a finite consistent representation of all CCS and TCSP programs exist. However sublanguages which allow finite representations are discerned. On the other hand the construction of predicate/transition nets is possible for all CCS programs in which every choice and every recursive body starts sequentially.

This volume contains a selection of papers presented at the Seventh Logic Programming Conference that took place in Tokyo, April 11-14, 1988. It is the successor to the previous conference proceedings published as Lecture Notes in Computer Science Volumes 221, 264 and 315. The book covers various aspects of logic programming such as foundations, programming languages/systems, concurrent programming, knowledge bases, applications of computer-aided reasoning and natural language processing. The papers on foundations present theoretical results on "narrowing", a proof strategy for proving properties of Prolog programs based on inductionless induction and several issues in nonmonotonic reasoning. Of special interest to mathematicians is the paper on computer-aided reasoning, which describes a system for assisting human reasoning. Natural language application papers treat the lexical analysis of Japanese sentences, a system that generates a summary of a given sentence and a new knowledge representation formalism suited for representing dynamic behavior by extending the frame system.

Using formal methods for the specification and verification of hardware and software systems is becoming increasingly important as systems increase in size and complexity. The aim of the book is to illustrate progress in formal methods based on Petri net formalisms. It presents both practical and theoretical foundations for the use of Petri nets in complex system engineering tasks. In doing so it bridges the gap between Petri nets and the systems modeling and implementation process. It contains a collection of examples arising from different fields, such as flexible manufacturing, telecommunication and workflow management systems.

This volume is a collection of the most important contributions presented at the second MFDBS conference held in Visegrád, Hungary, June 26-30, 1989. The papers selected from more than one hundred submissions, originating from 23 countries in 4 continents, can be roughly divided into the following sections: theoretical fundamentals of relational databases, logical foundations and databases, data modelling, database design, deductive databases, transaction management and security, concurrency control and distributed databases. The volume reflects the current state of knowledge and is a guide to further development in database theory.

This volume contains several invited papers as well as a selection of the other contributions. The conference was the first meeting of the Soviet logicians interested in com- puter science with their Western counterparts. The papers report new results and techniques in applications of deductive systems, deductive program synthesis and analysis, computer experiments in logic related fields, theorem proving and logic programming. It provides access to intensive work on computer logic both in the USSR and in Western countries.

Proceedings -- Parallel Computing.