Abstract: With the evolution of the global information infrastructure, service providers will need to provide effective and adaptive resource management mechanisms that can serve more concurrent clients and deal with applications that exhibit Quality of Service (QoS) requirements. Flexible, scalable and customizable middleware can be used as enabling technology for next generation systems that adhere to the QoS requirements of applications that execute in highly dynamic distributed environments. To enable application aware resource management, we are developing a customizable and composable middleware framework called CompOSE|Q based on a reflective metamodel. In this paper, we describe the architecture and runtime environment for CompOSE|Q and briefly assess the performance overhead of the additional flexibility. We also illustrate how flexible communication mechanisms can be supported efficiently in the CompOSE|Q framework.