Research On Service Composition For Multimedia Service Overlay Network

With the rapid development of Web service, more and more service providers provide multimedia applications in form of Web service. However, the function of services above is single and limited. How to make use of services composition technology to provide users with available multimedia services becomes a practical and significance subject. In order to stady the problem of service composition for multimedia applications, depending on the characteristic that Web services can form an overlay network on application layer, this thesis proposes a framework of service composition based on multimedia service overlay network. Then according to the framework, the service discovery, service routing and failure recovery of service path are investigated in detail. Providing users with intelligent integration service by service composition could satisfy users'dynamic requirements of function and non-function. The main contributions of the thesis are as follows:(1) A framework of service composition is proposed based on multimedia service overlay network for requirements of Internet-scale distributed multimedia application. This thesis proposes MSON, a framework of services combination based on multimedia service overlay network of multimedia service, in order to improve multimedia application's quality of service (Qos), flexibility and scalability. Depending on service composition model and composite multimedia service model, MSON adopts a hierarchical structure to simplify the complex service composition, by isolating its basic function unit and establishing hierarchical model-MSON. Then MSON can provide a consistent framework for the distributed multimedia application, and can improve the flexibility and of scalability multimedia application.(2) A distributed method of semantic service discovery is proposed for the service discovery in MSON. Since the traditional method of service discovery, cannot deal with the distributed search and semantic match, the thesis proposes a special distributed method of semantic service discovery for MSON. The method advertises semantic services on the registration nodes, and improves search efficiency by Bloom filter. The method makes use of pre-computation to avoid the reasoning operations which consume lots of time and then improve efficiency of service match. Considering the management of trust and reputation, the thesis proposes a QoS-based service selection and ranking algorithm. According to users'feedback, service providers'data and creditable agents' reports, the algorithm calculates the anticipated QoS value, which is depended on selecting and ranking services.(3) QoS service routing algorithm is proposed for finding service path in MSON. MSON completes the composition of services by mapping requirements of multimedia application to routing of overlay network. Hence, based on the plane overlay topology and hierarchical overlay topology, the thesis studies the algorithm of service routing and proposes two routing algorithm, including KTA-LBSPSA which the QoS-satisfied the plane service routing algorithm and HQSRA which is QoS-awared hierarchical service routing algorithm. KTA-LBSPSA firstly searches the service paths which satisfy QoS in least-delay service tree, and secondly selects the service path for which the fairness value is maximized as the ultimate service path from those candidate paths. Then we can get a load balancing service path which also meets QoS constraints. HQSRA divides the process of finding service path into two steps (inter-cluster service path finding and intra-cluster service path finding). HQSRA can be used to find the QoS-aware service path in the large-scale hierarchical overlay network.(4) A minimum-interference service composition and recovery algorithm is proposed for the reliability of the service path. Since the node and link may fail on the service path in MSON, the thesis propose a general analytic framework to model the interference and its intensity to the end users. Based on this framework and according to the three routing selection principles (i.e. choose the local path recovery, reliable service paths and adjust service path passively), the Minimum Interference Service Composition and Recovery Algorithm (MISCR) is designed. The simulation results show that MISCR reduces the interference to end users from service interruption in comparison with the traditional algorithms, and achieves higher robustness and stability.