Research And Implementation Of QoS - Aware Web Service Group Evaluation

A Web service is a kind of software application identified by a URI,which can be advertised, located, and accessed through a group of encoded messages. Since Web services often collaborate each other to build a more complicate application, they should to be described in terms of functional capabilities and Quality of Service (QoS) properties. As the spectacular development of Web services, there are more and more services with similar or overlapped functions. To facilitate and speed up Web Services improvement, the similar web services can be grouped into communities. Thus users can select an ideal web service from the community. Many efforts aim at selecting a qualified web service by considering the QoS(Quality of Service). Some approach to rely on the utility function to select the optimal service, which requires users to express their preferences as weights that can be involved in calculating. But,for those who have specific preferences, it is difficult to make accurate weighting evaluations of QoS property. Besides, if some users’preferences are obscure, it may be difficult to obtain preference information and weights about QoS properties. For this reason,there is an urgent need to improve a selection method of Web services to those who have no clear preferences.The traditional method of QoS-aware Web services selection need accurate weights given by the users to empress their preferences of QoS property. A QoS-aware service evaluation method of the Web service is proposed to solve the problem of service selection of the users whose preferences are indeterminate. At first, This method need to obtain the history service evaluation information of each user who has selected a service. Then gathering the historical selection results to obtain the group evaluation of Web services in the community by social choice function of decision-making theory. We use Condorcet and Borda function to do group evaluation and comparison. And theoretical analysis and experimental verification presented to estimate the suitability and effectiveness of Web services group evaluation method. Theoretical analysis proved wether the proposed approach has the clarity, fairness, anonymity, monotonicity and consistency that an effective group evaluation methods should be had. The results showed that the Condorcet and the Borda function suitable for Web services group evaluation. Finally, a Web services group evaluation system has implemented according to the method proposed in this paper. The system realized the evaluation and order function for similar services in a community, and to validate the evaluation data obtained. Testing modules include fairness and consistency, monotonicity properties of the service sorting and system performance testing. It shows the effectiveness of Web services group evaluation method and the efficiency of the system.