QoS-Aware Middleware for Web Services Composition - A Qualitative Approach

One of the benefits of web services is their ability to participate in a web services composition process. Therefore, an end-to-end QoS infrastructure should be established. Work conducted in this domain is mainly focused on functional QoS requirements such as service response time, delay, cost, etc. In this paper, we target QoS from the prespective of data freshness and accuracy. Therefore, we propose the usage of the WS-Notification specification as a base medium capable of sensing and routing any information change at the level of web services using a publish-subscribe mechanism. We then propose an algorithm that is capable of identifying the point of information change within the context of multiple web services composition scenario. This is then followed with an appropriate re-computation of a subset of the pre-established, global service execution plan. Our contributions are three fold: first we highlight the importance of qualifyable QoS aspect related to the issue of web services composition and monitoring, second we describe an algorithm capable of capturing and reflecting the state of web services involved in the integration process, and finally we illustrate the usage of WS-Notification to aid in building such systems.