On the specification of non-functional properties of systems by observation

Domain specific languages play a cornerstone role in Model-Driven Engineering (MDE) for representing models and metamodels. So far, most of the MDE community efforts have focused on the specification of the functional properties of systems. However, the correct and complete specification of some of their non-functional properties is critical in many important distributed application domains, such as embedded systems, multimedia applications or e-commerce services. In this paper we present an approach to specify QoS requirements, based on the observation of the system actions and of the state of its objects. We show how this approach can be used to extend languages which specify behavior in terms of rules, and how QoS characteristics can be easily expressed and reused across models. We show as well how this approach enables the specification of other important properties of systems, such as automatic reconfiguration of the system when some of the QoS properties change.