Dependability verification for contextual/runtime goal modelling

A static and stable operation environment is not a reality for many systems nowadays. Context variations impose many threats to systems safety, including the activation of context specific failures. Goal-oriented requirements engineering (GORE) brings forward the ‘why’ of system requirements, i.e., the intentionality behind system goals and the means to meet then. A runtime goal model adds a behaviour specification layer to a conventional design goal model, and a contextual goal model specifies the context effects over system goals, means and qualitative metrics. In order to formally verify the dependability of a CRGM, we propose a new goal-oriented dependability analysis based on the probabilistic model checking technique. In particular, we define rules for the transformation of a CRGM into a DTMC model that can be verified for the reliability of the fulfilment of one or more system goals. Also, to mitigate the analysis overhead and increase the usability of our proposal, we have successfully implemented and integrated a CRGM to DTMC code generator to the graphical tool that supports the goal modelling and analysis phases of the TROPOS development methodology. The resulting contextual dependability verification reflects the system requirements in a CRGM, which may represent: a system-to-be, whose verification would take place at design-time; or a running system, whose behaviour can be verified at runtime as part of a self-adaptation analysis targeting dependability.