Systematic Refinement of CPS Requirements using SysML, Template Language and Contracts

Abstract

In these day we encounter the transition from traditional closed and restricted-purpose embedded systems towards networked Cyber-Physical Systems. This applies to many industries, but in particular to the automotive industry, where assistance and automated driving functions are shaped out of complex combinations of functions and electronic control units, and even the car as a whole becomes part of a larger network of many vehicles plus infrastructure. And still, verifiable assertions must be available in the end to satisfy the safety case. The specification skills in industry often turn out to be insufficient. Even today, the mandatory V-model is hard to apply in practice and expressing appropriate requirements and refinements along with the evolution of the architecture is a hard thing to do. When development becomes agile and centered around component reuse, things become even more complex. We report about our experience with the application of contract-based development and explain keystones of our approach. We present a new template language called SSPL that allows the specification of requirements and assertions on every system architecture level and show how contract-based requirements refinement can go hand in hand with architecture refinement in SysML. We further present our Eclipse-based tool SAVONA that enables practical application of the approach.