Introducing Semi-Formal Specifications into a Distributed Development Process

Abstract

In Europe, the development of safety-critical rail IT is regulated by the Common Safety Method (CSM~352) and CENELEC standards EN 50126 to EN 50129. The CSM requires the railway undertaking to unambigously specify requirements on Equipment. The infrastructure branch of German Railways (DB Netz) has chosen to base the specifications of interlockings and related equipment like field element controllers on SysML Statecharts. Although these specifications will be more consistent and precise than the text-based ones in use before, this approach faces opposition from manufacturers who find it difficult to justify the correctness of their implementation. This paper reports on the approach, its motivation and its practical difficulties, and it endeavours to identify its merits and weaknesses.