Simplifying the Formal Verification of Safety Requirements in Zone Controllers Through Problem Frames and Constraint-Based Projection

• Published in: IEEE transactions on intelligent transportation systems Vol. 19; no. 11; pp. 3517 - 3528
• Main Authors: Yuan, Zhengheng, Chen, Xiaohong, Liu, Jing, Yu, Yijun, Sun, Haiying, Zhou, Tingliang, Jin, Zhi
• Format: Journal Article
• Language: English
• Published: New York IEEE 01.11.2018; The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
• Subjects: Complexity; Complexity theory; constraints; Control systems; Decomposition; Feasibility studies; formal verification; Intelligent transportation systems; Mathematical analysis; Problem frames; Problem frames approach; Projection; Safety; Software; Tracking; zone controller
• ISSN: 1524-9050; 1558-0016
• DOI: 10.1109/TITS.2018.2869633

Formal methods have been applied widely to verifying the safety requirements of communication-based train control (CBTC) systems, while the problem situations could be much simplified. In industrial practices of CBTC systems, however, huge complexity arises, which renders those methods nearly impossible to apply. In this paper, we aim to reduce the state space of formal verification problems in zone controller, a sub-system of a typical CBTC. We achieve the simplification goal by reducing the total number of device variables. To do this, two projection methods are proposed based on problem frames and constraints, respectively. The problem frame-based method decomposes the system according to sub-properties through functional decomposition, while the constraint-based projection method removes redundant variables. Our industrial case study demonstrates the feasibility through an evaluation, confirming that these two methods are effective in reducing the state spaces of complex verification problems in this application domain.