An Overview of the Model Driven Architecture

A major focus of the Object Management Group (OMG) today is the development of the Model Driven Architecture (MDA).  The MDA is a not single standard but a body of standards, or framework, that is used to support a general approach to system development.  The MDA seeks to accomplish the following goals: 

• Protect the investment made in modeling a system while providing the agility to implement that system on any number of different platforms, that is, to insulate the model from the underlying implementation technology

• Provide the means of transforming a model to the code suitable to operate on specific implementation platforms

The MDA is about increasing the value of modeling -- particularly Unified Modeling Language (UML) models -- by not obsolescing models as technology changes and by increasing the functionality provided by the models themselves.

To accomplish these goals, the MDA posits three perspectives in the development of software:

• The Computation Independent Model, or CIM, represents the 'business model' of an application domain that is independent of any IT concerns.  The CIM can be seen as representing the requirements of the system from the business perspective.  Currently, the modeling techniques for the CIM perspective are poorly defined within the MDA.

• The Platform Independent Model, or PIM, represents a model of an application that is IT-oriented but which is abstracted from specific implementation considerations.  The PIM serves a similar purpose with respect to system development as does the logical database model within database design.

• The Platform Specific Model, or PSM, enhances the PIM with specific considerations relevant to a particular implementation platform.  For example, a PSM might represent the PIM as mapped to Enterprise JavaBeans (EJBs).  The PSM is similar to the physical database design in database modeling.

The UML is, of course, a well-defined modeling language for the PIM.  The PSM is handled by extending UML with profiles that define elements for representing platform-specific elements within UML.  (The UML4EJB is a UML profile that tailors standard UML modeling elements, such as classes, to represent elements native to the EJB platform, such as entity beans.)  Areas of the MDA currently under development include the CIM and a model transformation language.

For more information on the MDA, visit http://www.omg.org/mda/  Other works on MDA include David Frankel, Model Driven Architecture:  Applying MDA to Enterprise Computing, John Wiley & Sons (2003) and Anneke Kleppe, et. al., MDA Explained, Addison-Wesley (2003), ISBN 0-321-19442-X.

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