An approach to the measurement of software evolution

Our current work involves developing methods of measuring changes to evolving software systems. We study a system's change characteristics over a large number of builds using the distinct sources of variation in the software metrics used to measure the system. We have been collaborating with a flight software technology development effort at the Jet Propulsion Laboratory (JPL) and have progressed in resolving the limitations of our earlier work in two distinct steps. First, we have developed a repeatable and consistent fault enumeration methodology, allowing them to be precisely and accurately measured. Second, we have developed a practical framework for automating fault measurement, which we applied to the JPL software system during its development. Every change to the system was measured and every identified fault was tracked to a specific code module. Our analysis indicates that measures of the evolving system's structure are strongly related to the number of faults inserted during its development, and that some types of change are more likely to result in the insertion of faults than others. The fault enumeration methodology ensures that the resulting fault model has greater predictive validity; it also provides a higher quality model than other popular definitions of a fault. Copyright © 2005 John Wiley & Sons, Ltd.