VDM specification of an interlocking system and a simulator for its validation

摘要

It has been long time since microcomputer systems were introduced into railway signalling areas. Software in the systems is becoming more and more complex in order to cope with higher system safety requirements and more sophisticated functions. Formal methods for railway safety-critical software are expected to help us construct reliable and correct systems. Although formally specifying a system has many advantages. it is also true that formal methods are difficult for unfamiliar and non-professional people. This is totally against our aim. We have, therefore, developed a simulator system, which illustrates user's interlocking specification, written in a formal specification language, on a computer graphical screen. Using this system, software designers and users can communicate easily and rigorously. Considering portability and making independent each function of the simulator, we made the modules of the simulator communicate through the inter-processes communication facility of UNIX. We could run each module in a different workstation scattering around the world through Internet.