Parents up

Knut Jetlund edited this page Jan 19, 2015 · 7 revisions

Back to diagram design


This page is inspired by rule four in Geert Bellkeens' blog post 5 rules for better UML diagrams.

The elements that are highest in a hierarchy should also be placed highest in a diagram. In other words:

  • Subclasses should be placed bellow their parents.
  • In aggregation relationships, the element on "whole-side" should never be bellow the element on the "part-side".
  • For realizations, the original element should be on top.

In the first diagram bellow, subclasses are placed above their mothers. This makes it difficult to understand the hierarchy in the diagram: Parents up - wrong

Instead, the subclasses should be aligned bellow their mother, like in the figure bellow: Parents up

The figure bellow illustrates an aggregation, with the "whole-side" on top. This is also a hierarchy since DQ_EvaluationMethod is a part of DQ_Element.

Whole side up

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