Dealing with fuzzy QoS properties in service composition

Service oriented applications are composed by orchestrating sets of cooperating services and are further offered as services themselves. Many applications have a dynamic character, needing to chose at runtime which service implementations to compose. When multiple possibilities exist, the choice is made according to the user preferences for certain Quality of Service (QoS) parameters. In this work we propose an approach for QoS-aware selection and composition of services, in the presence of both vague user preferences and vague service descriptions. The central elements of our approach are an extensible QoS ontology and a compositional model for vague QoS properties in workflow service composition.