The design of distributed safety critical software using CSP

Generally speaking, traffic control systems using signals are basically complex distributed control systems. These large-scale systems and networks are made up from interacting hierarchically structured subsystems. In order to control such highly complex systems, conventional mechanisms have become inefficient and impractical. The reliance on sophisticated computer control systems to manage such systems and networks is now becoming increasingly essential in order to match with ever growing demands and needs. As the traveling public are the primary clients of these systems, their safety must be ensured. In order to design and develop such safety critical software with high degree of correctness, a systematic and logical method is therefore necessary. This paper presents the use of the formal system Communicating Sequential Processes (CSP) with a complementary CSP interpreter as powerful toolset. CSP provides a model not only for the separate discrete event processes which constitute the system, but also for the interactions among them. The CSP interpreter provides an automatic tool for specifications written in CSP. These tools can be efficaciously applied by control and software engineers to initiate their designs, especially in the early stage of software development where ideas have to be tested out efficiently for their correctness and feasibility