Sub-composite service enabled QoS-aware service composition

QoS-aware service composition is to compose a composite service by selecting atomic services from service providers to maximize QoS while satisfying all the QoS constraints imposed by user requests. Many proposed schemes for service composition are atomic task oriented (ATO). Due to the possible large number of tasks contained in a composite service and the wide range of candidate services capable of accomplishing each task, the problem size of service composition can be very large for atomic task oriented schemes at runtime. This paper proposes a sub-composite service enabled (SCSE) scheme to downgrade the problem size of service composition at runtime, along with the re-use of existing execution plans for sub-composite services, to reduce the time for service composition. Experiments show that the proposed scheme outperforms atomic task oriented schemes when the problem size of service composition is large.