Design, Measurement and Verification of Scania’s Platform Software Architecture for Safety Related Embedded Systems

Abstract: The platform software architecture for the safety related embedded systems developed by Scania has become increasingly more complex. High complexity raises both the risk of failures and the time consumed by software developers to understand and debug the source code. This leads to increased software maintenance costs, which according to [24] can be between 60% and 75% of the total cost of software development. The purpose of this Master’s thesis is to investigate how a part of Scania’s current software architectural design can be further developed in order to decrease the complexity and the maintenance costs, without compromising with the essential functionality and performance. Another goal is to provide a solution that complies with the software safety requirements from ISO 26262, which Scania is planning to be able to fulfill in the future. To be able to compare our proposal for the software architecture with Scania’s current solution, a measurement tool has been developed. This tool measures the software quality metrics coupling and cohesion, which together with other software metrics gives an estimation of the architecture’s complexity. The verification of the software architecture with regards to ISO 26262 has been done using contract theory. The thesis work has resulted in alternative solutions for the software architectural design of the pressure sensor driver and the real-time database in one of Scania’s electronic control units. These solutions comply better with ISO 26262 and have lower complexity than Scania’s current solution in terms of coupling, cohesion and size of software components. This has been achieved by restructuring the software architecture and avoiding reuse of common software functions. The main conclusion of the thesis is that there is great potential for Scania to reduce the complexity of the platform software architecture and comply with ISO 26262.