Tom Graves' On layers in enterprise-architecture
questions the role of layers in EA.
I beg to differ. Greatly.
True, EA layers today are not consistent in meaning even when coming from the same organisation. Take for instance TM Forum's. But representations come from different eras and people sometimes. Some come from marketing rather than technical people.
But that does not mean that layers are not useful.
EA is a representation of the enterprise. And we have to use abstract patterns to represent the enterprise such as layers or tiers for some.
Layers are useful because, while still part of the big picture, they enable the separation of concerns in describing and developing a complex system.
The key layer abstractions are
- the Business layer which would describe the functional structure and operation of the enterprise without introducing implementation details. See picture below.
- the Technology layer describes the resources that implement the operation of the business layer.
- the People layer that depicts the human resources organization executing the processes in the business layer and operating the applications in the technology layer.
FFLV EA Layers: Business, Technology and People
Information exists in abstract in the business layer and it is stored and processed in the technology and people layers.
Layers have many sub-layers. For instance IT technology may consist of Applications and Infrastructure.
The infrastructure sub-layers has its own (sub-)layers such as Networks, Systems, Storage...
Nevertheless, the Business layer is always on top, since it defines what technology and people do. It is implemented/executed by the Technology and People layers.
The People organization is best placed at the bottom of the layers stack since people man the technology above as well.
Strategy is not a layer. It consists of a set of directions that guide the transformation of enterprise composed of the three layers stack.
In terms of typical architectures
- The business layer is described by the Business Architecture
- The technology layer is described (partially) by the EA IT architecture, typically the main scope of the EA today; Technology is more than IT though and EA is more than IT architecture
- The people layer is described by the Organization chart, at least. Not really covered in EA today.
The EA is composed of all the architectures above, in integration.
Tom is right when observing that layers can be seen as viewpoints that often come in isolation. Hence they can be differently and confusingly interpreted.
Unfortunately, it is true that most current EA frameworks describe one layer alone or have incomplete or out of context layers.
The right approach for layers is to see them in the context of an entire EA framework that describes their components and links, that is, that integrates the layers and their architectures.
Check the FFLV
that describes such a layered framework of the whole enterprise, not only IT, this post
among others or the two Kindle books.