AbstractDesign and maintenance of enterprize applications is complicated due to dependencies on technical requirements of the middleware framework. Especially, porting enterprise applications to another middleware layer or even new versions thereof requires a lot of handiwork and coding, since abstraction-, transformation-, and refinement steps have to be performed. Transformations should be assisted by a tool set which facilitates the migration process from one to another middleware platform. This paper presents GREAT, a rule-based transformation framework which facilitates transformations among models on the same or different abstraction levels. The feasibility of GREAT is shown by the transformation of a real world application conforming to EJB standard 1.1 into a version which complies to EJB standard 2.0.