Concurrency Theory: Calculi an Automata for Modelling Untimed and Timed Concurrent Systems

Intheworldweliveinconcurrencyisthenorm.Forexample,thehumanbody isamassivelyconcurrentsystem,comprisingahugenumberofcells,allsim- taneously evolving and independently engaging in their individual biological processing.Inaddition,inthebiologicalworld,trulysequentialsystemsrarely arise. However, they are more common when manmade artefacts are cons- ered. In particular, computer systems are often developed from a sequential perspective. Why is this? The simple reason is that it is easier for us to think about sequential, rather than concurrent, systems. Thus, we use sequentiality as a device to simplify the design process. However, the need for increasingly powerful, ?exible and usable computer systems mitigates against simplifying sequentiality assumptions. A good - ample of this is the all-powerful position held by the Internet, which is highly concurrent at many di?erent levels of decomposition. Thus, the modern c- puter scientist (and indeed the modern scientist in general) is forced to think aboutconcurrentsystemsandthesubtleandintricatebehaviourthatemerges from the interaction of simultaneously evolving components. Over a period of 25 years, or so, the ?eld of concurrency theory has been involved in the development of a set of mathematical techniques that can help system developers to think about and build concurrent systems. These theories are the subject matter of this book.

Concurrency Theory is a synthesis of one of the major threads of theoretical computer science research focusing on languages and graphical notations for describing collections of simultaneously evolving components that interact through synchronous communication. The main specification notation focused on in this book is LOTOS. An extensive introduction to this particular process calculus is given, highlighting how the approach differs from competitor techniques, such as CCS and CSP.

The book covers linear-time semantics, based on traces; branching-time semantics, using both labeled transition systems and refusals; and true concurrency semantics, using (bundle) event structures. In addition, the book discusses communicating automata approaches (both finite and infinite state); how the theory can be generalised to the timed setting; and, finally, the authors generalise the (finite and infinite state) communicating automata notations to yield timed automata and discrete timed automata.

This book represents a comprehensive pass through the spectrum of concurrency theory research: From untimed to timed syntax and semantics and process calculi to automata. Researchers and practitioners in the field of concurrency theory, as well as MSc and PhD students, will find the comprehensive coverage in this book essential reading.