A Publish/Subscribe Based Information Dissemination Model for QoS of Web Services

Quality of service (QoS) information for Web services is essential to QoS-aware service management. Currently, most work assumes that the overall QoS of a composite service can be computed by the pre-existing QoS information of component services. However, the issue of how to obtain these QoS information has largely been overlooked. Current research on this problem usually involves query-based or monitoring-based methods. However, in a dynamic service oriented computing (SOC) environment, these solutions suffer from some or all of the limitations, such as cost, timeliness guarantee and scalability. In this paper, a P2P based publish/subscribe model is proposed to disseminate new revised QoS information of Web services, which not only maintains the scalability of the underlying Chord network, but also improves reliability and timelines guarantee especially for QoS information obtainment. The authors suggest specialized rendezvous points(RPs) and a replica mechanism to reduce the risk of subscriptions loss and consequently improve reliability. A reverse RP ring is designed to quicken subscription delivery and QoS information publication. In addition, an optimization mechanism for composite services is built into the proposed model, which helps to reduce notification traffic. Simulation results show that the model is featured by low cost, high efficiency and scalability, which is suitable to large-volume QoS information distribution.