Due to the increasing interest in the model driven architecture (MDA) paradigm, the conceptual models have become the backbone of the software development process. So far some methods exist to develop a user interface according to a MDA-compliant method, none of them explicitly connects usability to their process activities. In this paper, we present a framework which incorporates usability as part of a MDA development process. In particular, a usability model for early evaluation is proposed. Using this model, the usability of a software system is evaluated and improved at the platform independent model (PIM) level. It focuses on the correspondences between the abstract user interface elements and the final user interface elements in a specific platform (CM). This framework has been successfully applied to an industrial MDA tool