An empirical study of software architectures' effect on product quality

Software architecture is concerned with the structure of software systems and is generally agreed to influence software quality. Even so, little empirical research has been performed on the relationship between software architecture and software quality. Based on 1141 open source Java projects, we calculate three software architecture metrics (measuring classes per package, normalized distance, and a new metric introduced by us concerning the excess of coupling degree) and analyze to which extent these metrics are related to product metrics (defect ratio, download rate, methods per class, and method complexity). We conclude that there are a number of significant relationships between product metrics and architecture metrics. In particular, the number of open defects depends significantly on all our architecture measures.