Abstract
Service composition is the process of automatically constructing a workflow from individual services so as to satisfy user requirements. When composing service workflows, it is important that both functional and non-functional requirements need to be considered. The so-called QoS-aware service composition is typically formulated analogous to the classical MMMKP optmization problem, and does not account for service and QoS dependencies which are often indispensable in real life. In this paper, we consider QoS-aware service composition in the presence of service-dependent QoS and propose a novel method that dynamically refines the composed workflow in light of QoS dependencies and user-provided topological and QoS constraints. Through evaluations, we demonstrate that our approach is capable of offering significant improvements in performance on real life scenarios with complex service and QoS dependencies.