Timing issues are of growing importance for the conceptualization and design of computer-based systems. Timing may simply be essential for the correct behaviour of a system, e.g. of a controller. Even if timing is not essential for the correct behaviour of a system, there may be good reasons to introduce it in such a way that suitable timing becomes relevant for the correct behaviour of a complex system. This book is unique in presenting four algebraic theories about processes, each dealing with timing from a different point of view, in a coherent and systematic way. The timing of actions is either relative or absolute and the underlying time scale is either discrete or continuous.

Timing issues are of growing importance for the conceptualization and design of computer-based systems. Timing may simply be essential for the correct behaviour of a system, e.g. of a controller. Even if timing is not essential for the correct behaviour of a system, there may be good reasons to introduce it in such a way that suitable timing becomes relevant for the correct behaviour of a complex system. This book is unique in presenting four algebraic theories about processes, each dealing with timing from a different point of view, in a coherent and systematic way. The timing of actions is either relative or absolute and the underlying time scale is either discrete or continuous. All presented theories are extensions of the algebra of communicating processes. The book is essential reading for researchers and advanced students interested in timing issues in the context of the design and analysis of concurrent and communicating processes.

SoSL was the first International Workshop on Semantics of Specification Languages, held from 25-27 October 1993 in Utrecht, the Netherlands. The workshop was organized by the Department of Philosophy of Utrecht University with financial support from the Nationale Faciliteit Informatica of the Nederlandse Organisatie voor Wetenschappelijk Onderzoek (NWO), and under the auspices of the British Computer Society'S specialist group in Formal Aspects of Computing Science (BCS FACS). The concern of the workshop was the semantics of specification languages, and the issues closely related to this area, such as type checking and the justification of proof rules and proof obligations. Its aim was the exchange of problems and ideas in this field of formal methods, and the identification of common programs of work for further investigation. The program of SoSL consisted of 3 invited lectures presenting the developments of the semantics of 3 major specification languages. Furthermore, there were 16 presentations of submitted papers. This volume provides a direct account of the workshop. It contains 3 papers that match the invited lectures and the 16 selected papers. The editors want to thank all those who have contributed to the workshop; the Program Committee and the referees for selecting the contributed papers, the invited speakers for their interesting talks, the Organizing Committee for all their efforts, and of course the participants. We have the feeling that the workshop was worthwhile and should be repeated.