Run-Time Adaptation of Non-functional Properties of Composite Web Services Using Aspect-Oriented Programming

Existing web service composition and adaptation mechanisms are limited only to the scope of web service choreography in terms of web service selection/invocation vis-à-vis prespecified Service Level Agreement constraints. Such a scope hardly leaves ground for a participating service in a choreographed flow to re-adjust itself in terms of changed non functional expectations and most often these services are discarded and new services discovered to get inducted into the flow. In this paper, we extend this idea by focusing on run-time adaptation of non-functional features of a composite Web service by modifying the non-functional features of its component Web services. We use aspect-oriented programming (AOP) technology for specifying and relating non-functional properties of the Web services as aspects at both levels of component and composite. This is done via a specification language for representing nonfunctional properties, and a formally specifiable relation function between the aspects of the component Web services and those of the composite Web service. From the end users’ viewpoint, such upfront aspect-oriented modeling of non-functional properties enables on-demand composite Web service adaptation with minimal disruption in quality of service. We demonstrate the applicability and merits of our approach via an implementation of a simple yet reallife example.