From Trust to Dependability through Risk Analysis

The importance of critical systems has been widely recognized and several efforts are devoted to integrate dependability requirements in their development process. Such efforts result in a number of models, frameworks, and methodologies that have been proposed to model and assess the dependability of critical systems. Among them, risk analysis considers the likelihood and severity of failures for evaluating the risk affecting the system. This approach then proposes to contain the risk level within acceptable values by adopting adequate countermeasures. In our previous work, we introduced the Tropos Goal-Risk framework, a formal framework for modeling, assessing, and treating risks on the basis of the likelihood and severity of failures. In this paper, we refine the Goal-Risk framework introducing the notion of trust for assessing risks on the basis of the organizational setting of the system. The assessment process is also enhanced to analyze risks along trust relations among actors. To make the discussion more concrete, we illustrate the framework with a case study on partial airspace delegation in Air Traffic Management (ATM) system.