Stochastic Model Checking for Predicting Component Failures and Service Availability
When a component fails in a critical communications service, how urgent is a repair? If we repair within 1 hour, 2 hours, or <inline formula><tex math notation="LaTeX"$n$/tex math><alternatives><inline graphic xlink:href="sevegnani ieq1 2650901.gif"/alternatives>/inline formula> hours, how does this affect the likelihood of service failure? Can a formal model support assessing the impact, prioritisation, and scheduling of repairs in the event of component failures, and forecasting of maintenance costs? These are some of the questions posed to us by a large organisation and here we report on our experience of developing a stochastic framework based on a discrete space model and temporal logic to answer them. We define and explore both standard steady state and transient temporal logic properties concerning the likelihood of service failure within certain time bounds, forecasting maintenance costs, and we introduce a new concept of <italic>envelopes of behaviour</italic> that quantify the effect of the status of lower level components on service availability. The resulting model is highly parameterised and user interaction for experimentation is supported by a lightweight, web based interface.
IEEE Transactions on Dependable and Secure Computing