What is Quality Tree

The chapter introduces a quality of Web service model which can be exploited by a Web service broker during the Web service selection phase. The model considers both user and provider standpoints. On the one hand, providers express their capabilities with respect to measurable dimensions (e.g., response time, latency). On the other hand, users can define the requirements with a higher level of abstraction (e.g. performance). Since the quality is subjective by definition, the presented quality model also maps the user preferences, i.e., how much a quality dimension is more important than another one in evaluating the overall quality. The Analytic Hierarchy Approach (AHP) has been adopted as a technique for expressing user preferences. The chapter also describes how the model can be exploited in the Web service selection process. Starting from a set of functionally equivalent Web services, the selection process identifies which are the Web services able to satisfy the user requirements. Moreover, according to a cost-benefit analysis, the list of selected Web services is sorted and, as a consequence, the best Web service is identified.