State-of-the-art context- and QoS-aware dynamic middleware platforms use information about the environment, in order to evaluate alternative configurations of an application and select the one that best meets the user?s QoS requirements. The specification of the alternatives is prepared at designtime and associated with the software during deployment. From the information and requirements in the specification, the middleware can synthesis, filter, and compare the alternative application configurations.

This paper presents a platform independent specification, referred to as service plan, which contains information elements for specifying configurations, dependencies on the environment, and QoS characteristics. The service plan is specified at a conceptual level to ensure that it can be implemented in a wide range of middleware platforms. The paper describes how the concept is used during deployment, instantiation, and reconfiguration. From the implementation and validation the expressiveness and usefulness of the service plan concept is assessed.