Masashi Asuka

An approach to specifying and verifying safety-critical systems with practical formal method SOFL

One of the primacy concerns in developing computer embedded safety-critical systems is how to develop quality software. Software must fulfill 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-Object-based-Formal Language). Requirements specification focuses on the functionality of the software, but with the consideration of safety constraints and its interaction with the surrounding operational environment. The verification of specifications can be carried out using three techniques: data flow reachability checking, specification, testing, and rigorous proofs, respectively. We apply this approach to a realistic railway crossing controller for a case study and analyzes its result.

Discharging proof obligations from atelier b using multiple automated provers

We present a method to discharge proof obligations from Atelier B using multiple SMT solvers. It is based on a faithful modeling of Bs set theory into polymorphic first-order logic. We report on two case studies demonstrating a significant improvement in the ratio of obligations that are automatically discharged.

Applying SOFL to specify a railway crossing controller for industry

This paper describes an application of the formal engineering method SOFL (Structured-Object-based-Formal Language) to specifying a realistic railway crossing controller for potential use in industry. As the railway crossing controller is a safety critical and real-time system, this application demonstrates the capability of SOFL for developing safety-critical and real-time systems and provides a foundation for implementing such a software controller in practice. It also shows that appropriate integration of structured methods with graphical notation, formal notation, and natural language offers a good readability and traceability as well as an effective mechanism for reducing complexity of systems.

A combined approach of microscopic and macroscopic simulation for rail traffic

The paper presents a combined approach of rail traffic simulation using suitable models, both microscopic and macroscopic. In rail traffic, train motions do not depend directly on preceding train motions, as in road traffic, but only on the speed limit in the current block section. Using the history of the speed limit in each block section, simulation of the movement of individual trains between stations can be performed independently. Based on this fact, we have formed a new microscopic model and proposed a combined approach, applying the macroscopic model to normal train runs and the microscopic model to othes. Our combined approach makes it possible to obtain quick responses by macroscopic simulation and detailed results by microscopic simulation.