El Miloudi El Koursi

Colored Petri Nets formal transformation to B machines for safety critical software development

Reaching the critical software safety requirements is one of the most important and complex tasks for the safety-related industry. This fact explains, as it was highly recommended by the CENELEC standard, the increasing use of formal means in the development process. However, industrial environments are still reticent facing difficulties in incorporating those formal methods in a larger scale of application, especially because of their mathematical modeling complexity. The present paper proposes a Petri Nets-based approach for safety critical software development using a formal transformation into B abstract machines. This work presents formal definitions for the translation of Colored Petri Nets to B abstract machines. As part of the French research project called “PERFECT”, it aims at enabling a stronger combination of formal design techniques and analysis tools in order to cope with the real complexity of critical software development and to prove in an automated manner that the final software product satisfies all safety requirements. Therefore, the use of the B method will broaden the scope of its applicability by providing a new input modeling alternative. An illustrative application of the transformation practical use is shown in this paper for a railway level-crossing case study.

Human factors in the analysis of the 'tram-car drivers' at intersections

The modern tramway has resurfaced as the cure to today?s urban transport problems such as pollution, road congestion and uneven access to transit. However trams at intersections often experience frequent and extended delays due to vehicles crossing the tram tracks. There is an increased potential for conflict between trams and vehicles at these locations and crashes are common. The question of the effects of human factors on trams crossroads safety has been little dealt with in literature. The general aim of this article is to further knowledge about the influence of tramway and surrounding environment on car?s driver behavior at intersections. Understanding these influences, involve conducting a systematic review of the cognitive tasks related to driving and identifying the hazards that can arise at each task, and what factors can make these more or less likely to arise, considering the environmental design at intersections and behavioral factors. To achieve that, the Hazop approach is conducted for this study. Concerning data collection, the methodology includes site visits to record user behavior and questionnaires to determine the opinion, concerns and knowledge of car drivers in interaction with the tram environment.

An HCPN Pattern for Railway Safety Critical Scenarios Formal Modeling

Analyzing railway critical scenarios usually involves a large team of diverse railway abilities and skills. This paper presents a formal modeling pattern for Hierarchical Colored Petri Nets (HCPN) in modeling railway safety critical scenarios. Indeed, under the French project called “PERFECT”, our long-term objective is to formalize and automate a significant part of railway scenarios modeling. The purpose of this contribution is to bring a first proposition of a standardized modeling way able to deal with the models complexity resulting from the various modeling capabilities for railway scenarios. In fact, HCPN modeling freedom is preventing from accurate information aggregation and a beneficial use of those models in an overall safety analysis. The proposed pattern is based on modular High Level Petri Nets and consists in describing all the railway scenario episodes while incorporating most relevant safety components of the system, such as safety regulation procedures, interlocking and even human involvement, enabling a larger gathering of information and allowing the study of diverse issues in a same global model. This work intends to bring a concrete and reusable HCPN pattern for modeling in order to facilitate studies of accidental scenarios considering automatic mechanisms and human tasks. A concrete application of the pattern was made for the real accidental scenario of “Saint Romain en Gier”.Copyright