8 years, 11 months ago

Enterprise Architecture and abstraction layers

I recently read John Gotze’s thoughts on the updated national enterprise architecture framework and its underlying meta-model published by the Danish Government Agency for Digitisation. The framework is named ‘OIO EA’ and has evolved over a number of years into the official national government architecture approach.

In his critique, John highlights that the updated meta-model captures key artefacts at the wrong layer of abstraction. For instance, business rules are located in the government strategy layer and thus tightly coupled to the long term vision of the government agency:

“In my view, Business Rules should not be located at the strategic level at all, so I obviously have issues with the metamodel. Like Uffe Donslund, our local BR-geek, I would argue that Business Rules primarily “belongs” to the Business sub-architecture domain.The metamodel at the strategic level should either way reflect several more concerns than it currently does. By comparison, the EA3 strategic metamodel is also focusing on Goals, but then has another scope by connecting to performance measures and investments.”

I agree strongly with John on this viewpoint. Business rules are operationalisations of the long term strategy and strategic intent. Whilst the vision, mission, and purpose of the enterprise do not change very often (i.e. provide the best available services our citizens), the business rules and processes involved in realising this will definitely change. Business rules belong in the business architecture.

Had the Government Agency for Digitisation used the Integrated Architecture Framework (IAF) — or any similar method — for this, one would have been forced to think in terms of abstractions and layering. IAF divides all architectural aspect areas (business, information, information systems and so on) into four distinct abstraction layers:

  1. Contextual – Why?
  2. Conceptual – What?
  3. Logical – How?
  4. Physical – With What?

This fundamental architectural distinction ensures proper separation of concerns across all architecture views and constructs. It is clear that aspirational consideration such as enterprise mission, vision, and long-term objectives belong to the contextual layer, whereas business rules are operational aspects, which are considered through a combination of conceptual (i.e. structural rules), logical (guiding principles and policies)., and physical entities (detailed business rules and decision logic for to-be process flows). This approach ensures:

  1. Loose coupling between building blocks and architecture constructs;
  2. Flexibility and resilience in architecture designs (i.e. certain elements can be replaced without impacting on other levels of the final solution architectures); and
  3. A simple, rigorous method and consistent designs.

IAF is by no means the only framework and method stipulating the use of simple abstraction layers. The difference is that IAF highlights the very importance of this up front – as opposed to a particular way of describing an architecture amongst others.

Choosing such an approach could possibly improve the aforementioned metamodel and keep business concerns at their appropriate level of abstraction.