Model Based Requirements Analysis and Testing of Automotive Systems with Timed Usage Models

In the automotive industry requirements are often still composed of natural language text, spreadsheets, drawings, and formal models. Models are often used to describe partial aspects from the whole set of requirements. Hence, flaws and vagueness in requirements are common and hard to discover. Upcoming standards like ISO 26262 request the automotive industry to be more strict and formal on the requirements. Formal notation and unambiguitiy is explicitely stated. In the field of system and acceptance testing requirements are the basis for all activities. Although, requirements are often not close to testing. To overcome this we introduced the Timed Usage Model (TUM) as a formal representation of requirements specification. During the creation of the model the requirements are analyzed and brought into an unambiguous and formal representation. Traceability is achieved, as each path in the model must be based upon a requirement. The formulation of the requirements in form of an unambiguous model clarifies the requirements and helps to detect design errors. During the creation of the model omissions and flaws in the requirements are discovered. The model serves as a communication medium when functionality responsibles are involved to clarify these aspects. Timed Usage Models were created for power train functionality and the energy management. Moreover, the model as a formalized representation of the requirements served as the basis for the whole testing process, including test planning, test case generation, and test campaign analysis.