Specifying safety-critical embedded systems with statecharts and Z

In this paper we introduce a formal approach for the specification of safety-critical embedded systems. The specification formalisms Z and statecharts are integrated under a suitable structural model. The combined approach uses the advantages of the formalisms while avoiding their disadvantages. The different formalisms yield different, compatible views on the system: the functional view describing data and data-transformation, the reactive view, describing the system's reaction upon external stimuli, and the structural view, describing the components of the system and their interaction. The combination is discussed presenting parts of a case study: a traffic light control system. The case study is oriented at original planning documents. Besides its safety- and real-time-aspects, the case study is particularly interesting because structuring and reuse is of considerable importance in this example.