Formal approach to development of critical computer applications

A formal approach to development of safety-related systems is presented. Three levels of system representation are treated within the common framework of temporal logic. The highest level is conceptual modeling, where the system is perceived from a global perspective. The conceptual model covers the part of the environment that is relevant from the safety point of view. The architectural model provides a different insight to the system: the components of the architecture are described individually, from the local perspective, and their interconnections are given by the structure specification. The lowest level represents the program, which is responsible for the behaviour of the logical (nonphysical) elements of system architecture. The approach is demonstrated by developing a simple railway crossing system