The Model-Driven Architecture (MDA)

The Model-Driven Architecture (MDA) defines an approach to modeling that separates the specification of system functionality from the specification of its implementation on a specific technology platform. In short it defines a guidelines for structuring specifications expressed as models. The MDA promotes an approach where the same model specifying system functionality can be realized on multiple platforms through auxiliary mapping standards, or through point mappings to specific platforms. It also supports the concept of explicitly relating the models of different applications, enabling integration and interoperability and supporting system evolution as platform technologies come and go.

in other words

Model Driven Architecture (MDA). The MDA is based on the idea that a system or component can be modeled via two categories of models: Platform Independent Models (PIMs) and Platform Specific Models (PSMs). PIMs are further divided into Computation Independent Business Models (CIBMs) and Platform Independent Component Models (PICMs). As the name implies PIMs do not take technology-specific considerations into account, a concept that is equivalent to logical models in the structured methodologies and to essential models within usage-centered techniques. The CIBMs represent the business requirements and processes that the system or component supports and the PICMs are used to model the logical business components, also called domain components. PSMs bring technology issues into account and are effectively transformations of PIMs to reflect platform-specific considerations.