Toward autonomic Web services trust and selection

Emerging Web services standards enable the development of large-scale applications in open environments. In particular, they enable services to be dynamically selected and bound. However, current techniques fail to address the critical problem of selecting the right service instances. The right service instances should be determined based on user preferences and business policies in a manner that considers their trustworthiness.; We propose a multiagent approach that naturally provides a solution to the selection problem. This approach is based on an architecture and programming model in which agents represent applications and services. The agents support considerations of semantics and quality of service (QoS). They interact and share information, in essence creating an ecosystem of collaborative service providers and consumers. Consequently, our approach enables applications to be dynamically configured at runtime in a manner that continually adapts to the preferences of the participants. Our agents are designed using decision theory and make use of Semantic Web knowledge representation techniques for shared conceptualizations (ontologies).; Our primary contribution is a model of trust, based on QoS, and constructed from the perspective of individual agents. We evaluate the system and the trust model empirically, via simulation experiments. The results show that our solution: (1) Captures simple quality preferences of service consumers and allows their agents to make automated service implementation selections. (2) Exhibits self-adjusting trust (in the sense of autonomic computing). That is, using the trust model, service consumers' agents are able to continually select the correct service implementations as the QoS exposed by the service implementations varies. (3) Captures complex preferences of service consumers. The improved model accounts for multiple QoS preferences, multiple quality tradeoffs, as well as semantic and statistical relationships between qualities.