Introduction

One of the main trends in recent developments in computer systems and programming languages is the inclusion of concurrency (or parallelism) and nondeterminism. Consequently, much recent research is devoted to the theory of these two modes of computation. A major direction within this theory is concerned with the semantics of programming languages expressing concurrency and nondeterminism and with verification of concurrent and nondeterministic programs. Among the new problems that the study of concurrency and nondeterminism encountered is that of fairness. This issue has revealed itself in many different contexts, as many facets of some very basic phenomenon. Some research directions, such as denotational semantics, had to solve some difficult mathematical problems (e.g. the power domain [PL 76, S 78, LE 76]); others, such as partial correctness proofs, needed some new insights (e.g. the discovery of noninterference [OG 76], [LA 77] and of cooperation [AFR 80], [LG 81] embodying relations among proofs). No research topic, however, raised controversy as much as the issue of fairness: Is it a “legitimate” (whatever that may mean) feature to be included in a programming language? Is it a “legitimate” area of study within computer science (as opposed to pure mathematics)?