Using SCR to Specify Requirements of the Bart Advanced Automated Train Control System

Since its introduction in 1978, the SCR (Software Cost Reduction) tabular notation has been used to represent the requirements of numerous safety-critical systems, including avionics systems, space systems, and control systems for nuclear plants. Our group has formulated a state-machine semantics for the SCR notation and a set of software tools for analyzing requirements specifications in the SCR tabular notation. To demonstrate the benefits of the SCR method for developing safety-critical systems, this chapter describes the application of SCR to a complex portion of the Advanced Automated Train Control (AATC) system under development for the Bay Area Rapid Transit (BART) system. Examples from an SCR specification of the required behavior of the AATC system are provided. The positive impact of applying our approach to the construction of the AATC system is summarized, and some important issues raised during the case study are discussed.