Abstract-This paper aims at analyzing empirically the quality evolution of an open source software using metrics. We used a control flow based metric (Quality Assurance IndicatorQi) which we proposed in a previous work. We wanted to investigate if the Qi metric can be used to observe how quality evolves along the evolution of the successive released versions of the subject software system. We addressed software quality from an internal perspective. We performed an empirical analysis using historical data on the subject system (Apache Tomcat). The collected data cover, in fact, a period of more than seven years (thirty-one versions in total). Empirical results provide evidence that the Qi metric reflects properly the quality evolution of the subject system.

The study presented in this paper aims at analyzing empirically the quality of evolving software systems using metrics. We used a synthetic metric (Quality Assurance Indicator - Qi), which captures in an integrated way different object-oriented software attributes. We wanted to investigate if the Qi metric can be used to observe how quality evolves along the evolution of software systems. We consider software quality from an internal (structural) perspective. We used various object-oriented design metrics for measuring the structural quality of a release. We performed an empirical analysis using historical data collected from successive released versions of three open source (Java) software systems. The collected data cover, for each system, a period of several years (4 years for two systems and 7 years for the third one). We focused on three issues: (1) the evolution of the Qi metric along the evolution of the subject systems, (2) the class growth of the subject systems, and (3) the quality of added classes versus the quality of removed ones. Empirical results provide evidence that the Qi metric reflects properly the quality evolution of the studied software systems.

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This paper aims at investigating empirically the applicability of Lehman's laws of software evolution using software metrics. We used a synthetic metric (Quality Assurance Indicator-Qi), which captures in an integrated way different object-oriented software attributes. We wanted to investigate if the Qi metric can be used to support the applicability of Lehman's laws of software evolution. We focused on the laws related with continuing change, increasing complexity, continuing growth and declining quality. We performed an empirical analysis using historical data on two open source (Java) software systems. The collected data cover a period of more than four years (fifty-two versions) for the first system and more than seven years (thirty-one versions) for the second one. Empirical results provide evidence that the considered Lehman's laws are supported by the collected data and the Qi metric.