The Metrô Rio case study

This paper reports on the Simulink/Stateflow based development of the on-board equipment of the Metrô Rio Automatic Train Protection system. Particular focus is given to the strategies followed to address formal weaknesses and certification issues of the adopted tool-suite. On the development side, constraints on the Simulink/Stateflow semantics have been introduced and design practices have been adopted to gradually achieve a formal model of the system. On the verification side, a two-phase approach based on model-based testing and abstract interpretation has been followed to enforce functional correctness and runtime error freedom. Formal verification has been experimented as a side activity of the project.Quantitative results are presented to assess the overall strategy: the effort required by the design activities is balanced by the effectiveness of the verification tasks enabled by model-based development and automatic code generation.

► Introduction of formal modeling and code generation reduces bugs.
► Introduction of model-based testing and abstract interpretation reduces verification cost.
► Formal verification can be performed with a cost that is lower than the one required by testing.