Methodological Support for FormallySpecifying Safety - Critical

We present the concept of an agenda and apply this concept to the formal speciication of software for safety-critical applications. An agenda describes a list of activities to solving a task in software engineering, and validations of the results of the activities. Agendas used to support the application of formal speciication techniques provide detailed guidance for speciiers, schematic expressions of the used speciication language that only need to be instantiated, and application independent validation criteria. We present an agenda for a frequently used design of safety-critical systems and illustrate its usage by an example. Using agendas to systematically develop formal speciications for safety-critical software contributes to system safety because, rst, the speciications are developed in a standardized way, making them better comprehensible for other persons. Secondly, using a formal language yields speciications with an unambiguous semantics as the starting point of further design and implementation. Thirdly, the recommended validation criteria draw the speciier's attention to common mistakes and thus enhance the quality of the resulting speciication.