Research On Web Service Selection Based On QoS And Reputation

As the number of Web services with the similar function is increasing, QoS-based service selection at runtime has become an important research topic. The existing QoS-based services selection approaches always assume that the QoS attributes coming from service providers and reputation coming from consumers are effective and trustworthy, which is actually impossible in reality. So, it looks forward to a reliable, trustworthy service selection method. This thesis proposes a service selection approach considering QoS data and reputation based on the researches we have already had, The main efforts are as followings.(1)A model of Web services selection is proposed on the basis of traditional Web services publish and discovery model. In the novel model, the UDDI registry is enhanced with QoS information, and two new roles, selection agent and reputation manger. The selection agent is accounted as a broker between a service consumer, a UDDI registry and a reputation manager to select the Web services that satisfy calculation of QoS values and service matching, computing and sorting algorithm. The reputation manager collects feedback regarding the QoS of the Web services from the service consumers, calculates reputation scores, and realizes consumer evaluation algorithm. The impartiality and trustworthiness characteristics of QoS information and consumers'feedback are ensured.(2)A service selection which classifies and computes the source of the QoS attributes and reputation is proposed in this thesis. For the QoS attributes whose data come from service providers, the statistics of past runtime data to revise the providers'QoS data are used, thus effectively solving the factors of service quality attributes'unreliability. For reputation whose values come from consumers, the values based on probability statistics theory and time forgetting factor are computed. Reputation measurement is affected evolution trend and fluctuation of QoS. Then, through the use of subjective reputation with QoS attribute values, the optimal service is selected by service matching, computing and sorting algorithms. Last, consumers and rating become credible through consumer evaluation algorithm.(3)In order to prove the feasibility and effectiveness of Web service selection mechanism, we implement a demo program to carry out simulation experiment . The experiment's result shows that the mechanism proposed in this thesis can not only guarantee the availability, but also improve the coverage.