The notion of partial and evolutionary specification has gained attention both in research and industry in the last years. While many people regard this just as a process issue, we are convinced that it is as well a language problem. Unfortunately, UML is not expressive enough to deal with evolutionary information in the system. In this paper, we propose an extension to a graphic modeling language called ADORA which is developed in our research group. We conservatively extend the semantics of some ADORA constructs so that intentional incompleteness can be expressed in the language and define a calculus for refining such specifications. With the help of these extensions, evolutionary specifications can be written in a controlled and systematic way. As the language and its extensions are formally defined, the consistency of evolutionary refinements can be checked mechanically by a tool.