Depth of Inheritance Tree (DIT)

Overview

Inheritance, otherwise referred to as generalization, is a key concept in the object model and must be carefully used. A class situated too deeply in the inheritance tree will be relatively complex to develop, test and maintain. It is useful, therefore, to know and regulate this depth.

This metric provides the position of the class in the inheritance tree.

Computation

For multiple inheritance, this metric provides the maximum length path.

· DIT (C0) = 0

· DIT (C0’) = 0

· DIT (C1) = 1

· DIT (C2) = 2

· DIT (C3) = 3

· DIT (C4) = 4

Figure 23 - Depth inheritance computation for a class

Nominal range

Between 0 and 4.

Analysis

A compromise between the high performance power provided by inheritance and the complexity which increases with the depth must be found. A value of between 0 and 4 respects this compromise.

A value greater than 4 would compromise encapsulation and increase complexity.