QoS-aware middleware for ubiquitous and heterogeneous environments

Middleware systems have emerged in recent years to support applications in heterogeneous and ubiquitous computing environments. Specifically, future m iddle,ware platforms are expected to provide quality of service support, wh ich is required by a new generation of QoS-sensitive applications such as m edia streaming and e-commerce. This article presents four key aspects of a QoS-aware middleware system: QoS specification to allow description of appl ication behavior and QoS parameters; QoS translation and compilation to tra nslate specified application behavior into candidate application configurat ions for different resource conditions; QoS setup to appropriately select a nd instantiate a particular configuration; and finally, QoS adaptation to a dapt to runtime resource fluctuations. We also provide a comparison of exis ting QoS-aware middleware systems in these four aspects.