This book will attempt to give a first synthesis of recent works con- cerning reactive system design. The term "e;reactive system"e; has been introduced in order to at'oid the ambiguities often associated with by the term "e;real-time system,"e; which, although best known and more sugges- tive, has been given so many different meanings that it is almost in- evitably misunderstood. Industrial process control systems, transporta- tion control and supervision systems, signal-processing systems, are ex- amples of the systems we have in mind. Although these systems are more and more computerized, it is sur- prising to notice that the problem of time in computer science has been studied only recently by "e;pure"e; computer scientists. Until the early 1980s, time problems were regarded as the concern of performance evalu- ation, or of some (unjustly scorned) "e;industrial computer engineering,"e; or, at best, of operating systems. A second surprising fact, in contrast, is the growth of research con- cerning timed systems during the last decade. The handling of time has suddenly become a fundamental goal for most models of concurrency. In particular, Robin Alilner 's pioneering works about synchronous process algebras gave rise to a school of thought adopting the following abstract point of view: As soon as one admits that a system can instantaneously react to events, i. e.

This book will attempt to give a first synthesis of recent works con- cerning reactive system design. The term "e;reactive system"e; has been introduced in order to at'oid the ambiguities often associated with by the term "e;real-time system,"e; which, although best known and more sugges- tive, has been given so many different meanings that it is almost in- evitably misunderstood. Industrial process control systems, transporta- tion control and supervision systems, signal-processing systems, are ex- amples of the systems we have in mind. Although these systems are more and more computerized, it is sur- prising to notice that the problem of time in computer science has been studied only recently by "e;pure"e; computer scientists. Until the early 1980s, time problems were regarded as the concern of performance evalu- ation, or of some (unjustly scorned) "e;industrial computer engineering,"e; or, at best, of operating systems. A second surprising fact, in contrast, is the growth of research con- cerning timed systems during the last decade. The handling of time has suddenly become a fundamental goal for most models of concurrency. In particular, Robin Alilner 's pioneering works about synchronous process algebras gave rise to a school of thought adopting the following abstract point of view: As soon as one admits that a system can instantaneously react to events, i. e.