A UML model of a software system can be represented by a sequence of model transformations, starting from an empty model. To effectively support the design of complex systems, transformations help the developer to proceed from an initial requirements model to a platform-specific, executable model. We present a notion of potentially re-orderable model transformations that assist the developer in the design process, and track the semantic dependencies of the different modeling steps. Based on our experience with our own software engineering methodology and modeling tool, we outline a possible implementation that will support developers in revising their model, and still benefit from any subsequent effort that has been spent on model evolution, especially with regard to correctness of the evolving model. Keywords model transformation · model evolution