Abstract. We present a method to discharge proof obligations from Atelier B using multiple SMT solvers. It is based on a faithful modeling of B's set theory into polymorphic rst-order logic. We report on two case studies demonstrating a signicant improvement in the ratio of obligations that are automatically discharged.
One of the primary concerns in developing computer embedded safety-critical systems is how to develop quality software. Software must fulll its functional requirements and must not contribute to the violation of safety properties of the entire system. To this end, capturing error free and satisfactory functional requirements is crucial before proceeding to the subsequent development phases. We describe an approach to specifying and verifying software for safety-critical systems with the practical formal method SOFL (Structured-Objectbased-Formal Language). Requirements specication focuses on the functionality of the software, but with the consideration of safety constraints and its interaction with the surrounding operational environment. The verication of specications can be carried out using three techniques: data ow reachability checking, specication testing, a n d rigorous proofs, respectively. W e apply this approach to a realistic railway crossing controller for a case study and analyzes its result.
To improve the situation for crowded commuters in Japan, it is important to plan a train schedule that considers passenger behavior, such as their choice of trains and the transfer stations used to reach their destinations. However, it is difficult to directly measure such detailed behavior using the present infrastructures, with which we can only get OD (Origin-Destination) data from the automatic ticket gates. The obtained OD data only consists of the number of passengers for each origin-destination and the time each passenger passes through the gates. In this article, to contribute to the planning phase of a new train schedule, the authors propose a method for estimating railway passenger flow using OD data. This paper firstly points out that the problems of estimating passenger flow can be boiled down to a shortest path problem of graph theory by assuming a certain passenger behavior model. By representing train operations in a graph structure, we can assume that a passenger will use the minimum cost path to his/her destination. This paper secondly proposes a method for conducting fast searches of the graph structure. The method uses the fact that railways operate on a time schedule. This method can estimate passenger flow fast enough so as to apply it to a practical train schedule planning support system. Lastly, the authors show the results of applying the passenger flow estimation system to a railway in an urban area in Japan.
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