This paper presents a formal approach to analyze system reconfigurability, based on a Generic Component Model (GCM), which describes the system from the services provided by its components, and their organization into Operating Modes, in order to achieve specific objectives. Following a bottom-up approach, services provided by elementary components are used as resources for services at a higher level. Several versions exist when the same service can be rendered by using distinct sets of resources. Reconfiguration results from the existence of multiple versions, since a faulty resource does not imply loosing the services that use it. A level regulation example shows the effectiveness of the proposed model and tools.