UML Distilled: A Brief Guide to the Standard Object Modeling Language, Second Edition

Derived Associations and Attributes

Derived associations and derived attributes can be calculated from other associations and attributes, respectively, on a class diagram. For example, an age attribute of a Person can be derived if you know that Person's date of birth.

Each perspective brings its own interpretation of derived features on class diagrams. The most critical of these has to do with the specification perspective. From this angle, it is important to realize that derived features indicate a constraint between values, not a statement of what is calculated and what is stored.

Figure 6-8 shows a hierarchical structure of accounts drawn from a specification perspective. The model uses the Composite pattern (see Gamma, Helm, Johnson, and ...