Model-based Safety Assessment using OCL and Petri Nets

Safety becomes a primordial assessment in safety-related systems where human lives can be somehow put in risk, needing to comply with safety requirements defined by industry standards such as IEC 61508, ISO 26262 or DO-178C. Safety contracts are useful to specify these requirements (as assumptions and guarantees), thus assuring an expected level of confidence. To verify the safety requirements is measured to represent more than a half of the overall system development costs. In this paper, we propose a model-based verification that addresses safety verification from the early beginning of system development, thus saving costs. Namely, we use UML for system design and Object Constraint Language (OCL) for specifying safety contracts, while its verification is carried out using Petri nets. As case study, we assess the safety of an embedded system that models a fire prevention system in a hospital building.