Towards safety monitoring of ETCS level 2 with parametrized extended live sequence charts

ETCS is an European signalling, control and automatic train protection system. Even with the most advanced quality assurance techniques, correctness of ETCS is hard to be ensured within the development phases. In this paper, we use runtime verification to provide on-going protection during the operational phase. To define a suitable monitoring specification language, we propose a graphic formalism of parametrized extended live sequence charts (PeLSCs). The language of PeLSCs allows us to intuitively express parametric safety properties of ETCS. We generate monitors by translating PeLSCs into hybrid logic, and validate our monitors by simulation and error injection. We show that the complexity of the word problem of PeLSCs is linear in the sizes of traces, thus our formalism is well-suited for online monitoring of ETCS.