Deviation Analysis Through Model Checking

Inaccuracies, or deviations, in the measurements of monitored variables in a control system are facts of life that control software must accommodate—the software is expected to continue functioning correctly in the face of an expected range of deviations in the inputs. Deviation analysis can be used to determine how a software specification will behave in the face of such deviations in data from the environment. The idea is to describe the correct values of an environmental quantity, along with a range of potential deviations, and then determine the effects on the outputs of the system. The analyst can then check whether the behavior of the software is acceptable with respect to these deviations. In this report we wish to propose a new approach to deviation analysis using model checking techniques. This approach allows for more precise analysis than previous techniques, and refocuses deviation analysis from an exploratory analysis to a verification task, allowing us to investigate a different range of questions regarding a system’s response to deviations.