Evaluating software design processes by analyzing change data over time

An analysis is presented of early design and code change data from the software cost reduction (SCR) project, a well-reported effort conducted at the US Naval Research Laboratory from 1978 to 1988. The analyses are mostly time-based studies of the change data and relationships between the data and SCR personnel activity data. Some analyses of the change data show patterns consistent with a major goal of the SCR project: the design and development of easy-to-change software. Specifically, most changes took a day or less to uncover and resolve; the majority of changes updated at most one module. Moreover, these percentages remained fairly stable. No positive relationship appeared between error-correction effort and the number of days that an error remained in the SCR design documentation. Other analyses suggest that consistency may have been temporary. For example, the analyses suggest a stepwise growth in average change effort, and an increasing percentage of changes resulted in module interface updates. Certain specific ratios between SCR change data and personnel activity data may be possible indicators of design incompleteness.<>