4.2.4: Models and Patterns
Adopt Model-Based Architecture and Pattern-Based Design Other Information:
A best practice in the architecture discipline is to establish or adopt reference architectures and reference implementations
that can be used by project implementation teams to jump start their efforts. Commonly used architecture patterns are a form
of the reference architecture and reference implementation. • Pattern-based design incorporates both the concepts of reference
architectures as well as model based approaches. Architecture patterns exist at the design, build and runtime levels of the
architecture. • Model-based architecture (also referred to as model driven architecture, or MDA, by the Object Management
Group) is an approach to bridging the divide between business requirements and technical solutions. Similar to moving down
the rows of the Zachman Framework (The Zachman Institute for Framework Advancement (ZIFA), http://www.zifa.com), it involves
a progressively more detailed and specific set of models. These models range from the most abstract depiction of the business,
to a functionally complete, but platform- independent model, to a platform-specific specification from which code can be generated.
The advantage of this approach is the linkage between the different levels and the automated mechanisms for moving from one
level to the next. This provides traceability from the business requirements to the code and allows the impact of changes
to be identified and managed. Combined with SOA which allows the impact of changes to be isolated to particular services,
the model based approach holds great promise to enable flexibility in IT – the ability to quickly modify the code base necessary
to implement new capabilities. Agencies should begin to adopt model based approaches to application development and integrate
them into their service based SDLC. As they mature this capability, they should pursue pattern-based design techniques. However,
the use of model based and pattern based design techniques should be closely linked to effective technical performance measures.
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