QoS aspect languages and their runtime integration

Abstract. Distributed object middleware, such as CORBA, hides systemand network-speci c characteristics of objects behind functional interface speci cations. This simpli es development and maintenance of distributed objects, contributing to their growing acceptance. Critical applications have Quality of Service (QoS) requirements, however, such as real-time performance, dependability, or security, that are hidden bymiddleware. Because of this, application developers often bypass distributed object systems, thus gaining little or no advantage from the middleware. We have developed Quality Objects (QuO), a framework for developing distributed applications with QoS requirements. QuO provides a set of aspect languages, called Quality Description Languages (QDL), for specifying possible QoS states, the system resources and mechanisms for measuring and controlling QoS, and behavior for adapting to changing levels of available QoSatruntime. This paper describes QuO's aspect languages, their usage, and how they interact with the QuO runtime system to form the QuO framework.