The complexity of today's software systems leads to the creation of many related diagrams, representing different viewpoints, different levels of abstraction, and different implementation alternatives. Model-driven software engineering places these models in the center of the development process. Tool support is an essential aspect of model-driven engineering. Of particular interest are model transformation tools: they can facilitate the creation and the evolution of models; they provide a level of traceability between them and they help keeping them synchronized. Unfortunately, currently there are few such tools for UML-based models. This paper presents MEDAL, our model transformation tool. First, we present our viewpoint on model-driven software engineering. Then we describe MEDAL and how we implemented MEDAL on top of Rational XDE. Finally, in the last section we show how a web application development that is based on an architectural framework can be supported by the MEDAL tool.