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Software Architecture Guide

Architecture Principle Structure

Explanation

Section titled “Explanation”

The TOGAF principle template splits every principle into four parts. Each part has its own job. (The article on TOGAF covers the framework itself.)

Name. The name is a clear, memorable label for the rule. One example principle is Technology Independence.

Statement. The statement gives the fundamental rule. It must be short and leave no room for doubt. For example: applications should not depend on specific technology platforms.

Rationale. The rationale explains the business benefits of following the principle. Its arguments should support discussion. They should also relate to the stakeholders and their goals. A stakeholder is anyone with an interest in the system.

Implications. The implications list what it takes to carry out the principle. That means requirements, resources, costs and activities or tasks. TOGAF prescribes implications as part of the template.

Why the structure matters. Principles are meant to be enduring and seldom amended. They reflect consensus, guide future IT decisions and align with business objectives. A fixed structure puts the rule, the reason and the consequences in one place.

Qualities of a good principle. A secondary guide names five qualities: understandable, robust, complete, consistent and stable. Stable means the principle withstands the test of time and stays relevant.

For the general idea of a principle, see Architecture Principle.

Example

Section titled “Example”

A team writes a principle for a retail company.

  • Name: Technology Independence.
  • Statement: Applications do not depend on specific technology platforms.
  • Rationale: Applications can run on a variety of platforms. This serves the business goals of the stakeholders.
  • Implications: The team lists the requirements, resources, costs and tasks needed to keep applications free of platform dependence.

Trade-offs

Section titled “Trade-offs”

The facts describe the template and its purposes. They do not describe drawbacks. One point is worth noting: the template only works if each part is filled in. A principle without implications states a rule but hides what it requires.

Checks

Section titled “Checks”
  • Each principle has a Name, a Statement, a Rationale and Implications.
  • The Statement is short and states one fundamental rule without ambiguity.
  • The Rationale gives business benefits and relates to stakeholders and their goals.
  • The Implications list requirements, resources, costs and tasks for carrying out the principle.
Section titled “Related”

Sources

Section titled “Sources”