Decomposing scheme plans to manage verification complexity

Several formal methods have been proposed for the specification and safety verification of railway applications. In order to be successful they need industrial strength tools to support the animation, proof, model checking and simulation of such systems. The complexity of railway systems means that capability of the analysis tools have consistently been improving. In our approach we propose that the complexity of analysis of railway interlocking systems can also be managed through incremental addition of system detail and decomposition of system specifications themselves. We propose a domain specific language (DSL) which describes the core aspects of a railway interlocking system and demonstrate how we can identify suitable decompositions in terms of the DSL. The DSL informs our system engineering approach which uses a graphical editor to input railway scheme plans, supports the automatic generation of CSP || B specifications of the plans and uses the ProB tool for their animation and model checking.