Cooperating Sequential Processes

Abstract

The problems raised by the parallel execution of processes are examined, and the foundations of a theory of cooperating sequential processes are given. The applications are those in which the activity of a computer must include the proper reaction to a possibly great variety of messages thathcan be sent to it at unpredictable moments, logical problems which arise, for example, when speed ratios are unknown, communication possibilities restricted, etc, are dealt with. It is proposed that in each processof any complexity the variables occurring in it admit analogous hierarchical orderings, and that when these hierachies are clearly recognizable in the program text the gain in clarity of the program and in efficiency of the implementation will be considerable.