On universality of concurrent expressions with synchronization primitives

Abstract

AbstractConcurrent expressions are a class of extended regular expressions with a shuffle operator (‖) and its closure (). The class of concurrent expressions with synchronization primitives, called synchronized concurrent expressions, is introduced as an extended model of Shaw's flow expressions. This paper discusses some formal properties of synchronized concurrent expressions from a formal language theoretic point of view. It is shown that synchronized concurrent expressions with three signal/wait operations are universal in the sense that they can simulate any semaphore controlled concurrent expressions and they can describe the class of recursively enumerable sets. Some results on semaphore controlled regular expressions are also included to give a taste of more positive results