A hierarchical model for quality assessment of object-oriented designs

This dissertation describes a new hierarchical model for assessment of high level design quality attributes in object-oriented designs. In this model, structural and behavioral design properties of classes, objects, and their relationships are evaluated using a suite of object-oriented design metrics. Design properties such as encapsulation, modularity, coupling, and cohesion, are shown to influence high level quality attributes such as reusability, flexibility, and complexity. Empirical and anecdotal information is presented in defining relationships between design properties and individual quality attributes. The relationship or links from design properties to quality attributes are weighted in accordance with their influence and importance. Equations for the computation of quality attributes based on weighted design properties have been developed for the model. The model has been validated by using expert opinion to compare with the model results. An automated tool, QMOOD++, that implements the new hierarchical model for assessment of high level quality attributes in object-oriented designs has been developed. The tool and evaluation process has been used in the assessment of several large object-oriented systems in order to verify its effectiveness. The quality model and tool provide an opportunity for early and reliable quantitative assessment of object-oriented design quality. Designers and developers can now periodically evaluate designs and software using the model and tool, to ensure development of a product with desired quality measures based upon internal product characteristics.