GALS System Design

Abstract

This chapter focuses on the design of globally asynchronous, locally synchronous (GALS) systems, which were mentioned in Chap. 3. The polychronous semantic model of the Signal language has very interesting properties that favor a comfortable design of these systems. The implementation generated from a Signal model of a distributed system can be trustworthily guaranteed to be correct by construction regarding the expected message exchanges within the system. This chapter presents some basic elements for the correct design of GALS systems. In Signal, over the past decade, there have been significant studies on program distribution, mainly led by Benveniste and Le Guernic. This chapter is devoted to the results obtained from these studies and their applicability. Section 11.1 first indicates some application domains in which safe system distribution is crucial. Then, Sect. 11.2 presents some key notions that are usable to address system distribution issues. Finally, a methodology based on these notions is proposed in Sect. 11.3.