The Web Service Selection Based On Dynamic Updating And Comprehensive Evaluation Of QoS

With the fast growing of Web Services from technical concept to practical application, there are many web services with the same or similar function on the network. How to select the best service from many services that meet the functional requirements becomes the key issue in Web Services application. Thus, QoS(Quality of Service) is included in Web Services, and the research of Web Service Selection based on QoS is launched, that is the problem of determining and selecting the best service to meet the requirements of the service requester according to QoS information. Then how to select the best service according to QoS information becomes an urgent issue.Through the in-depth annlysis on the practical significance of QoS information, the characteristics and nature of QoS attributes, and the QoS requirements of service requester, this paper creates a web service selection model based on dynamic updating of QoS and comprehensive evaluation of QoS. The dynamic updating ensure the correctness and objectivity of QoS information, and make QoS information have reference value and guide significance in Web Service Selection. The comprehensive evaluation ensures to select the best service which meets the needs of service requester.Actual quality of web service is changing, so the real-time updating of QoS information must be ensured. After updating, QoS information should reflect the changes of actual quality of service and be consistent with most actual quality of service. On this basis, this paper proposes a dynamic updating strategy of QoS based on real-time computation and periodic revise. This strategy fully considers the individual characteristics and global characteristics of the feedback data from server and client, uses data to make current QoS information some degree of amendment, and at the same time of making QoS information after updating reflect the latest changes in the quality of service, makes QoS information be consistent with most actual quality of service. So this strategy ensures the correctness and objectivity of QoS ifnromation, and provides premise guarantee for QoS-based Web Service Selection.This paper also proposes a comprehensive evaluation strategy of QoS based on QoS expectations and QoS attribute weights. This strategy fully considers the QoS requirements of service requester, including the QoS expectations and QoS attribute weights, guarantees the selected best web service not only meet the QoS expectations of service requester, but alse meet the QoS attribute weights of service requester, and so ensure the best web service selected by QoS-based Web Service Selection meet the QoS requirements of service requester.According to the dynamic updating strategy and comprehensive evaluation strategy, the dynamic updating algorithm and the comprehensive evaluation algorithm are given and verified by experiments in this paper. The experiments show that the dynamic updating strategy of QoS and comprehensive evaluation strategy of QoS proposed in this paper are reasonable and effective, and can support QoS-based Web Service Selection.