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Software Architecture Guide

Enterprise Architecture Layers

Explanation

Section titled “Explanation”

An organization can describe itself in layers. Each layer answers a different question. Links between layers keep the whole picture consistent.

Four domains in TOGAF

TOGAF (see the article “TOGAF”) rests on four related areas called architecture domains: business, data, application and technology.

  • Business architecture covers strategy, governance, organization and key business processes.
  • Data architecture describes the structure of the organization’s logical and physical data assets.
  • Application architecture is a blueprint for the individual systems to be deployed.
  • Technology architecture is the fourth domain. See the article “Technology Architecture”.

Three layers in ArchiMate

The ArchiMate core framework uses three layers: business, application and technology. Each layer has passive structure, behavior and active structure.

  • The application layer supports business components with application services.
  • The technology layer provides hardware and communication infrastructure for the application layer.

How layers connect

Two kinds of link matter most.

  • Use (serving). Higher layers use the services of lower layers. This is the most important relation between layers.
  • Realization. A lower-layer element may realize a comparable higher-layer element. For example, a data object realizes a business object. Realization links tangible, physical elements (the “how”) to more abstract, logical ones (the “what”).

Realization can chain through derivation. An artifact realizes a data object. So it also indirectly realizes the business object. This gives traceability across layers: you can follow a business concept down to the artifact behind it.

Why it matters

Elements and relationships that cross layers make the architecture description coherent. This is the basis for aligning business and IT.

Example

Section titled “Example”

A small shop sells goods online. The business layer holds an “Order” business object. The data layer or application layer holds an “Order record” data object that realizes it. A file in the system, an artifact, realizes that record. If the shop changes what an order means, the team follows the links down. They see which data and which files are affected.

Trade-offs

Section titled “Trade-offs”

The facts here describe the layers and links, not their costs. One caution follows from them: the value of the layers depends on the cross-layer links. Layers described in isolation do not give a coherent description of the architecture.

Three layers with serving and realization links between them.

Diagram source 
flowchart TB
  B[Business layer: business process, business object]
  A[Application layer: application service, data object]
  T[Technology layer: technology service, node, artifact]
  A -- serves --> B
  T -- serves --> A
  A -. data object realizes business object .-> B
  T -. artifact realizes data object .-> A

Checks

Section titled “Checks”
  • The document names the layers or domains it uses (business, data, application, technology).
  • Cross-layer relationships (use/serving and realization) are shown, not just isolated layers.
  • Business objects can be traced through data objects to the artifacts that realize them.
  • The business layer covers strategy, governance, organization and key business processes.
Section titled “Related”

Sources

Section titled “Sources”