Survey of Modelling Formalisms for MISRA-C:1998 Software Architecture Modelling

Abstract: The complexity of electrical and electronic automotivesystems have increased steadily over the previous decades, with modern vehicles containing as many as 50-70 Elec-tronic Control Units, and several CAN-communication net-works. In order to address the increasing complexity of these safety-critical embedded systems, safety standards such as ISO 26262 are making their way to the market, posing strong restrictions on the development process of automotive systems in order to ensure safety. With cur-rent automotive actors possessing large existing source codebases for their ECUs, primarily written in the C program-ming language, the demands posed on software architec-tural models by ISO 26262 are proving to be a challenge tomeet given the difficulties of modelling low-level languages such as C. This thesis aims to survey currently existingmodelling formalisms with regards to their ability to modelautomotive embedded C source code in a way that facili-tates ISO 26262 compliance. A delimitation is made to theuse of the MISRA-C:1998 subset of the C programminglanguage, a safer subset commonly used in automotive in-dustry. A short ontology is proposed, coupled with a metric for evaluating the completeness of a modelling formalism. Requirements are posed on suitable modelling formalisms,and AADL, Lustre, SysML and Promela are identified as promising candidates for modelling embedded C code. Se-mantic constructions present in the C language are iden-tified, and a mapping between these constructions and se-mantic constructions present in the selected modelling for-malisms is made and analyzed using the completeness eval-uation framework that was proposed. Architectural De-scription Languages (ADL), such as AADL, are identifiedas being the most promising with regards to modelling em-bedded C code. Control Flow Graphs are identified as a promising augmentation to ADLs in order to deal with theirlack of control flow semantics.