A Formal Modeling and Verification Approach for Real-Time System

The next few years will see distributed real-time computer systems playing an important role in control systems of high-dependability applications, such as rail transportation. In these applications a failure in the temporal domain can be as critical as a failure in the value domain. In rail transportation, train control system has become more complex and the methods to ensure its correctness of have been considered outmoded. The safety of train control system is becoming increasingly important as computers pervade them on which human life depends and the failure to meet time deadline can have serious or even fatal consequences. This paper proposes a formal modeling and verification approach for real-time system. In the proposed method the real-time system is modeled by Timed Automata Network (TAN) and verified by model checking which explores the state space to determine whether the system satisfies a given specification. The case study of ATP (Automatic Train Protection) shows how the method can assist in designing more efficient and reliable real-time systems. Firstly, Automatic Train Protection (ATP) system and Timed Automata Network (TAN) model is proposed; secondly, the state transitions and multi-tasks ATP onboard model will be modeled with TAN model, and then the time sequences of each task are expressed in UML Sequence Diagrams. Finally, the timing characteristics will be verified to meet the requirement by UPPAAL model checker. A major conclusion of the survey is that formal methods, while still immature in some respects, can be used successfully to model and verify real-time systems.