Modeling and Reasoning with Decision-Theoretic Goals

Goal models have found important applications in Requirements Engineering as models that relate stakeholder requirements with system or human tasks needed to fulfill them. Often, such task specifications constitute rather idealized plans for requirements fulfillment, where task execution always succeeds. In reality, however, there is always uncertainty as to whether a specification can/will actually be executed as planned. In this paper, we introduce the concept of decision-theoretic goals in order to represent and reason about both uncertainty and preferential utility in goal models. Thus, goal models are extended to express probabilistic effects of actions and also capture the utility of each effect with respect to stakeholder priorities. Further, using a state-of-the-art reasoning tool, analysts can find optimal courses of actions/plans for fulfilling stakeholder goals while investigating the risks of those plans. The technique is applied in a real-world meeting scheduling problem, as well as the London Ambulance Service case study.