Web services provide a fundamental technology for developing service-oriented systems by leveraging platform-independent interface descriptions (WSDL) and a flexible message encoding (SOAP). Beside the functional description, Quality of Service (QoS) issues are currently not part of the Web service standards stack, although they provide valuable metadata of a Web service such as performance, dependability, security or cost and payment. This additional information can be used to greatly enhance service discovery, selection and composition. As a result of the latest research that is dedicated to this area, this chapter deals with the various ways of describing, bootstrapping and evaluating QoS attributes. A strong focus is laid on client-side QoS assessment and the arising problems. Furthermore, a method to analyze Web service interactions by using our evaluation tool and extract important QoS information without any knowledge about the service implementation will be presented and thoroughly explained. Usually, taking performance measures for a specific Web service requires access to the service implementation or at least the server machine where it is hosted. This chapter will address a way to bootstrap the most important performance and dependability values form the client’s perspective and therefore overcoming these restrictions.
Web Service Discovery with Quality of Service (QoS) Parameters using Bayesian Belief Network
