A behavioral notion of robustness for software systems

Software systems are designed and implemented with assumptions about the environment. However, once the system is deployed, the actual environment may deviate from its expected behavior, possibly undermining desired properties of the system. To enable systematic design of systems that are robust against potential environmental deviations, we propose a rigorous notion of robustness for software systems. In particular, the robustness of a system is defined as the largest set of deviating environmental behaviors under which the system is capable of guaranteeing a desired property. We describe a new set of design analysis problems based on our notion of robustness, and a technique for automatically computing robustness of a system given its behavior description. We demonstrate potential applications of our robustness notion on two case studies involving network protocols and safety-critical interfaces.