Fuzzy Goals for Requirements-Driven Adaptation

Self-adaptation is imposing as a key characteristic of many modern software systems to tackle their complexity and cope with the many environments in which they can operate. Self-adaptation is a requirement per-se, but it also impacts the other (conventional) requirements of the system; all these new and old requirements must be elicited and represented in a coherent and homogenous way. This paper presents FLAGS, an innovative goal model that generalizes the KAOS model, adds adaptive goals to embed adaptation countermeasures, and fosters self-adaptation by considering requirements as live, runtime entities. FLAGS also distinguishes between crisp goals, whose satisfaction is boolean, and fuzzy goals, whose satisfaction is represented through fuzzy constraints. Adaptation countermeasures are triggered by violated goals and the goal model is modified accordingly to maintain a coherent view of the system and enforce adaptation directives on the running system. The main elements of the approach are demonstrated through an example application.