Software Architecture (SA) allows for early assessment of and design for quality attributes of a software system, and it plays a critical role in current software development. However there is no consensus on fundamental issues such as design methods and representation organization and languages, and current proposals lack specificity and preciseness. Thus, it is extremely difficult to build a complete and appropriate software architecture, even though it is recognized as a fundamental artifact. In this paper we define an architecture design. method that enables the systematic and assisted construction of the SA of Enterprise Applications, taking into account major quality attributes involved in this family of systems. We apply Model-Driven Engineering techniques to achieve this goal. The architecture is treated as a mega-model (a model composed of related models) and the application Of design decisions is encoded in terms of model tran, formations. The architectural rationale is explicitly registered as the set of tran, formations that yields the complete SA from scratch. We illustrate the application of the approach by designing the SA of a case study from the literature.