Investigating the Applicability of Lehman's Laws of Software Evolution using Metrics: An Empirical Study on Open Source Software

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.