Combining Statecharts and Z for the Design of Safety-Critical Control Systems

In this report, we describe an approach that integrates a mathematical speci cation language with more traditional software design techniques to yield a practicable methodology for the speci cation of safety-critical control systems. To manage complexity and to foster separation of concerns, the system design model is divided into three views: the architectural view, speci ed with object and class diagrams; the reactive view, speci ed with statecharts; and the functional view, speci ed with Z. A systematic relationship between the reactive and the functional view entails proof obligations to guarantee semantic compatibility. We illustrate this approach with a case study on controlling a heavy hydraulic press.