Fortis: A Tool for Analysis and Repair of Robust Software Systems

This paper presents Fortis, a tool for automated, formal analysis and repair of robust discrete systems. Given a system model, an environment model, and a safety property, the tool can be used to automatically compute robustness as the amount of deviations in the environment under which the system can continue to guarantee the property. In addition, Fortis enables automated repair of a given system to improve its robustness against a set of intolerable deviations through a process called robustification. With these techniques, Fortis enables a new process for developing robust-by-design systems. The paper presents the overall design of Fortis as well as the key details behind the robustness analysis and robustification techniques. The applicability and performance of Fortis are illustrated through experimental results over a set of case study systems, including a radiation therapy system, an electronic voting machine, network protocols, and a transportation fare system.