Tutorials : Metrics for Object Oriented Software Development :

Depth of Inheritance (DIT)

Depth of Inheritance is the maximum length from a given class to the root of the inheritance tree. In Java, as all the classes inherit from Object class, the minimum DIT in Java is 1. It is a measure of the depth of the class hierarchy. The higher the value of DIT, child classes inherit more number of methods from the base classes. In such situations, it becomes too difficult to evolve the base classes and child classes. Thus, it is important to keep a low value of DIT in design.

Number of Children (NOC)

Number of Children is the immediate number of sub-classes to a base class. If we have a very large number of children to a base class, it might be a candidate for refactoring to create a more sustainable and maintainable hierarchy.

Conclusion

Area	Item	Metrics
Class	Method	WMC
	Collaboration	RFC
	Cohesion	LOMC
	Coupling	CBO
Inheritance		DIT
		NOC

The above table summarizes the areas that the discussed metrics can be applied to. By no means is this is a complete set of metrics that are available. There are plenty more like Lines of Code, Fan-ion/Fan-out etc. I suggest that interested readers go through them all in order to decide which metric is most suitable for his/her project. It is important to mention that depending on the size and complexities of the project, the set of metrics needs to be adjusted to get the right benefit. The decision of which ones to use is mostly down to the organizational practice and experience of individual professionals.

Samudra Gupta has more than 8 years of experience in the area of Java based application design and development. He works as an independent consultant in United Kingdom and at present provides consultancy in government tax regime and intelligence information system development. In past, he has provided expert consultancies in the Publication and Retail sector software development. He is the author of the book “Logging in Java with JDK1.4 Logging API and Apache Log4j”, Apress, April, 2003. He is a regular contributor to different Java magazines and journals like Javboutique, JavaWorld, Java Developers Journal, DevX etc. In his free time, he loves to play contract bridge and ten pin bowling.

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