Appraising fairness in languages for distributed programming

The relations among various languages and models for distributed computation and various possible definitions of fairness are considered. Natural semantic criteria are presented which an acceptable notion of fairness should satisfy. These are then used to demonstrate differences among the basic models, the added power of the fairness notion, and the sensitivity of the fairness notion to irrelevant semantic interleavings of independent operations. These results are used to show that from the considerable variety of commonly used possibilities, only strong process fairness is appropriate for CSP if these criteria are adopted. We also show that under these criteria, none of the commonly used notions of fairness are fully aceptable for a model with an n-way synchronization mechanism. The notion of fairness most often mentioned for Ada is shown to be fully acceptable. For a model with nonblocking send operations, some variants of common fairness definitions are appraised, and two are shown to satisfy the suggested criteria.