Towards a tool-based domain specific approach for railway systems modeling and validation

RSSRail 2019, International Conference on Reliability, Safety, and Security of Railway Systems. Modelling, Analysis, Verification, and Certification , Lille, FRANCE, 04-/06/2019 - 06/06/2019International audienceIn the railway field, graphical representations of domain concepts are omnipresent thanks to their ability to share standardized information with common knowledge about several railway mechanisms: track circuits, signalling rules. This paper proposes a domain specific approach for railway systems modeling and validation by combining the Model-Driven Engineering (MDE) paradigm and a formal method. First, an example of a graphical DSL is defined thanks to MDE tools, and then the formal B method is used to define its underlying operational semantics and to guarantee the correctness of the model's behaviour with respect to its safety properties. Our approach is assisted by the Meeduse tool which animates and visualizes execution scenarios of domain models. Starting from a given model designed in the DSL tool, Meeduse asks ProB to animate B operations and gets the reached state by means of B variables valuations. Then, it translates back these valuations to the initial DSL resulting in automatic modifications of the domain model. Our approach allows a more pragmatic domain-centric animation than current visual animation techniques since the resulting DSL tool allows domain experts, who are not necessarily trained in formal methods, to design and validate by themselves the various domain models

Formal modelling techniques for efficient development of railway control products

We wish to model railway control systems in a formally precise way so that product lines can be adapted to specific customer requirements. Typically a customer is a railway operator with national conventions leading to different variation points based on a common core principle. A formal model of the core product must be precise and manipulatable so that different feature variations can be specified and verified without disrupting important properties that have already been established in the core product. Cyber-physical systems such as railway interlocking, are characterised by the combination of device behaviours resulting in an overall safe system behaviour. Hence there is a strong need for correct sequential operation with safety “interlocks” making up a process. We utilise diagrammatic modelling tools to make the core product more accessible to systems engineers. The RailGround example used to discuss these techniques is an open source model of a railway control system that has been made available by Thales Austria GmbH for research purpose, which demonstrates some fundamental modelling challenges

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N-Heterocyclic carbene (NHC)-mediated polymerizations of N-butyl N-carboxyanhydride (Bu-NCA) to produce cyclic poly(N-butyl glycine)s (c-NHC-PNBGs) have been investigated in various solvents with NHCs having differing steric and electronic properties. Control over the polymer molecular weight (MW) and polymerization rate is strongly dependent on the solvent and the NHC structure. Kinetic studies reveal that the propagating intermediates for the polymerization in low dielectric solvents (e.g., THF or toluene) maintain cyclic architectures with two chain ends in close contact through Coulombic interaction. The NHCs not only initiate the polymerization, but also mediate the chain propagation as intramolecular counterions. Side reactions are significantly suppressed in low dielectric solvents due to the reduced basicity and nucleophilicity of the negatively charged chain ends of the zwitterions, resulting in quasi-living polymerization behavior. By contrast, the two charged chain ends of the zwitterionic species are fully dissociated in high dielectric solvents. The chain propagation proceeds as in conventional anionic polymerizations, wherein side reactions (e.g., transamidation) compete with chain propagation, resulting in significantly diminished control over polymer MW. The cyclic zwitterionic propagating species can be converted into their linear polymeric analogues (l-NHC-PNBGs) by end-capping with electrophiles (e.g., acetyl chloride) or the NHC-free cyclic analogues (c-PNBGs) by treatment with NaN(TMS) 2, as evidenced by MALDI-TOF MS, NMR, and SEC analysis. © 2012 American Chemical Society