The Model Driven Architecture is a framework for software development, defined by the OMG. Key to MDA is the importance of models in the software development process. Within MDA the software development process is driven by the activity of modeling your software system.
The MDA development life cycle is not very different from the traditional life cycle. The artifacts of the MDA are formal models, i.e., models that can be understood by computers. The following three models are at the core of the MDA:
Traditionally the transformations from model to model, or from model to code, are done mainly by hand. In contrast, MDA transformations are always executed by tools. Many tools have been able to transform a PSM to code; there is nothing new to that. What's new in MDA is that the transformation from PIM to PSM is automated as well.