Experimental Assessment ofthe E ect of Inheritance on the Maintainability ofObject - Oriented

In this paper, we describe an empirical investigation into the modiiability and understandability of Object-Oriented (OO) software. A controlled experiment was conducted to establish the eeects of varying levels of inheritance on understandability and modiiability. The software used in this experiment consisted of a C++ system without any inheritance and a corresponding version containing three levels of inheritance, as well as a second larger C++ system without inheritance and a corresponding version with ve levels of inheritance. For both of the systems, the application modelled a database for a University personnel system. A number of statistical hypotheses were tested. Results indicated that the systems without inheritance were easier to modify than the corresponding systems containing three or ve levels of inheritance. Also, it was easier to understand the system without inheritance than a corresponding version containing three levels of inheritance. Results also indicated that larger systems are equally diicult to understand whether or not they contain inheritance. The results contained in this paper highlight the need for further empirical investigations in this area, particularly into the beneets of using inheritance.