Research On QoS-Aware Service Composition In Service-Oriented Environment

As more and more computation, storage and information resources are being added into the service-oriented environment, it is important to address the issue of QoS-aware service composition. In the process of service composition, a composite service is composed of a group of component services. The quality of the composite service depends on the aggregation of the quality of the component services. Since the process of service composition consists of three stages, i.e. service discovery, service selection and service delivery, it's imperative and challenging to provide QoS guarantee for the component services at different stages of service composition in order to guarantee the quality of the composite service.First of all, at the stage of service discovery, traditional centralized service discovery faces the problem of performance bottleneck and single-point failure when it comes to massive QoS-aware service discovery. Structured P2P technology provides scalability to service discovery but cannot guarantee the data availability. Chord4S provides a distributed QoS-aware service discovery. In Chord4S, service providers can publish QoS descriptions. Service consumers can incorporate QoS constraints in service discovery. In order to enhance the data availability and guarantee the routing performance, Chord4S improves the data distribution method and routing protocol of Chord. Experimental results demonstrate that Chord4S provides an effective and efficient solution to distributed service discovery.Second of all, at the stage of service selection, if the selected service providers are incapable of delivering component services, the quality of the composite service will be violated. ServiceTrust help predict service providers'capability of service delivery by evaluating their reputation based on their historic service delivery performance. ServiceTrust can also resist the attacks of malicious reputation manipulation and QoS abuse. Experimental results demonstrate that ServiceTrust improve the success rate of service delivery and can well protect service consumers from the abovementioned attacks.Another issue that needs to be addressed at the stage of service selection is that service providers'capability and willingness to provide QoS is dynamic. Service consumers need to negotiate with service providers in order to guarantee their requirements for the quality of the composite services can be met. CASS (Combinatorial Auction for Service Selection) enables flexible and efficient combinatotiral-auction-based negotiation between service consumers and providers over multidimensional quality of the component services. Experimental results show that CASS can help the service consumers and providers determine the quality of the component services, which guarantees the quality of the composite services.Third of all, at the stage of service delivery, faulty component services must be adapted aiming at guaranteeing the quality of the composite service. A workflow-pattern-based adaptation method is proposed to confine the adaptation scope and help select worthwhile adaptation solution. Experimental results demonstrate that the proposed method can improve the success rate of quality guarantee for the composite service.Finally, a QoS guarantee framework based on autonomous agent is proposed to facilitate partially or completely automated service discovery, service reputation evaluation, QoS negotiation and service adaptation through interactions among autonomous agents.