This paper proposes a principled methodology for the realization of distribution transparencies. The proposed methodology is placed within the general context of Model-Driven Architecture (MDA) development. Specifically, it consists of a UML-based representation for the specification of platform independent models of a system. Moreover, it comprises an automated aspect-oriented method for the refinement of platform independent models into platform specific ones (i.e., models describing the realization of the system's distribution transparency requirements, based on a standard middleware platform like CORBA, J2EE, COM+, etc.). Finally, the proposed methodology includes an aspect-oriented method for the generation of platform specific code from platform specific models. Key words: Aspect-Oriented Modeling, Aspect-Oriented Programming, Refinement, Code Generation, Middleware PACS: