Quality-of-Service-Aware Service Selection: A Novel Approach Considering Potential Service Failures and Nondeterministic Service Values

In service-oriented systems, a variety of loosely coupled services are composed to support the execution of processes. One important research problem in this context concerns the selection of such services taking into account the values for the corresponding quality-of-service (QoS) attributes. Existing QoS-aware ex ante service selection approaches build on preferences and requirements for the QoS attributes and evaluate the available services by means of a utility value. For many reasons, such as software bugs, high server workload, or network failures, an ex ante optimal service may be temporarily unavailable or may fail during its execution, requiring replanning. Moreover, several QoS attribute values may be stochastic rather than deterministic. Thus, both the ex post realized QoS values and the corresponding utility may significantly differ from those that are ex ante computed. This could result in a substantial loss of resources. In this paper we present a novel approach for QoS-aware service selection considering both the effects of potential service failures and nondeterministic QoS values ex ante. The approach is founded on an expected utility calculus. We find that considering the effects of potential service failures and nondeterministic QoS values leads to substantially better decisions in QoS-aware service selection.