Formal Specification & Verification Process by using Z for Safety Improvement of Railway Signaling System

초록

Railway signaling systems is the safety critical system that controls the route and speed of the train. If this system malfunctions during operation, it could result in catastrophic materialistic and human damages. In Korea, the railway signaling systems recently switched to a computer based system from the pre-existing hardwired based system, which caused the system to adopt a more complicated structure. As a result, the issues regarding the reliability and safety of the system are constantly appearing on the social agenda. In order to resolve these issues, the international standard such as IEC and IEEE are recommending the standardization of the system during its development process as well as the standard proposal which will enable the documents to be created in a correct method especially at beginning step using formal method. So we study the procedure to establish requirements specification and verification suitable for Korean conditions based on international standard, and demonstrate the results of formal method application by using Z(Zed) language for mockup railway signaling system. We use Z language as formal specification and verification and here we propose specific process able to be utilized in practical railway industrial sites.