Post-Hoc Formal Verification of Automotive Software with Informal Requirements: An Experience Report

In this paper, we report on our experience with formally specifying and verifying an industrial software module, provided to us by a company from the heavy-vehicle industry. We start with a set of 32 informally stated requirements, also provided by the company. We discuss at length the formalization process of informally stated requirements for the purposes of their subsequent formal verification. Depending on the nature of each requirement, one of three languages was used: ACSL contracts, LTL or MITL. We use the Frama-C deductive verification framework to verify the source code of the module against the formalized requirements, with the outcome that 21 requirements are successfully verified while 6 are not. The remaining 5 requirements could not be verified for the module itself, as they specify behavior outside it. We illustrate what steps we took to convert LTL and MITL formulas into ACSL contracts to enable their verification in Frama-C. Finally, we discuss conclusions we drew from our work, notably that formal-verification-driven development of modules and verified breakdown of system requirements could likely remedy some problems we encountered.