Formal Integrity Analysis of Digital ATC Track Database

1. Introduction Railway signalling is a safety critical system. Special hardware for safety has been used in signalling systems. Recently computer has been widely introduced and software is much more responsible for safety. As far as hardware aspect of safety computer is concerned, there has been a lot of progress. Special devices for safety have been developed and used widely. But the safety technology of software is not matured yet. To increase safety of software, formal methods is expected to be a good solution. Specifications are written in formal specification languages. This enables the specification to be examined by computer. It is even possible that the specification is examined by automatic proofs. In this article, we have designed the specification of digital ATC (Automatic Train Control system) track database with a formal specification language, and analyzed with the mechanical proof. Finally our specification has proved its integrity. We report on the procedure and mention the possibility of the using formal methods and proofs.