Architecting in the Automotive Domain: Descriptive vs Prescriptive Architecture

To investigate the new requirements and challenges of architecting often safety critical software in the automotive domain, we have performed two case studies on Volvo Car Group and Volvo Group Truck Technology. Our findings suggest that automotive software architects produce two different architectures (or views) of the same system. The first one is a high-level descriptive architecture, mainly documenting system design decisions and describing principles and guidelines that should govern the overall system. The second architecture is the working architecture, defining the actual blueprint for the implementation teams and being used in their daily work. The working architecture is characterized by high complexity and considerably lower readability than the high-level architecture. Unfortunately, the team responsible for the high-level architecture tends to get isolated from the rest of the development organization, with few communications except regarding the working architecture. This creates tensions within the organizations, sub-optimal design of the communication matrix and limited usage of the high-level architecture in the development teams. To adapt to the current pace of software development and rapidly growing software systems new ways of working are required, both on technical and on an organizational level.