Narrow Results

We present an analysis of the evolution of a Web application project developed with object-oriented technology and an agile process. During the development we systematically performed measurements on the source code, using software metrics that have been proved to be correlated with software quality, such as the Chidamber and Kemerer suite and Lines of Code metrics. We also computed metrics derived from the class dependency graph, including metrics derived from Social Network Analysis. The application development evolved through phases, characterized by a different level of adoption of some key agile practices — namely pair programming, test-based development and refactoring. The evolution of the metrics of the system, and their behavior related to the agile practices adoption level, is presented and discussed. We show that, in the reported case study, a few metrics are enough to characterize with high significance the various phases of the project. Consequently, software quality, as measured using these metrics, seems directly related to agile practices adoption.

The term "software entropy" refers to the tendency for software, over time, to become difficult and costly to maintain. A software system that undergoes continuous change, such as having new functionality added to its original design, will eventually become more complex and can become disorganized as it grows, losing its original design structure.

A recent study show that software degradation may be measured using the WMC expressed in terms of Shannon entropy. In this paper we extended the empirical analyses also to RFC and CBO since these CK metrics have been shown to be correlated with fault-proneness of OO classes.

We analyzed various releases of the publicly available Eclipse and Netbeans software systems, calculating the entropy of some CK metrics for every release analyzed. The validity is shown through a direct measure of software quality such as the number of detected defects. Our results display a very good correlation between the entropy of CBO and RFC and the number of bugs for Eclipse and Netbeans.

Complexity and quality metrics are in general computed on every system module while the entropy is just a scalar number that characterizes a whole system, this result suggests that the entropy of some CK metrics could be considered as a global quality metric for large software systems. Our results need, however, to be confirmed for other large software systems.