We propose an approach that aims to provide services that are able to adapt at run-time to the quality of services (QoSs) required and expected by the users in the context of an adaptive resource management system. When requiring a service, users may specify additional information which is of two types: QoSs (i.e., the print resolution or the transmission bandwidth) and properties (i.e., the location of the resource that provides the service or the provider of the service). In the adaptivity process, both types of information are mapped on the QoSs and properties of the underlying system?s resources, which are explicitly represented through architectural reflection. As a consequence, resources try to adapt their QoSs to those required by the current service.