Investigation of the risk to software reliability and maintainability of requirements changes

In order to continue to make progress in software measurement, as it pertains to reliability and maintainability, we must shift the emphasis from design and code metrics to metrics that characterize the risk of making requirements changes. Although these software attributes can be difficult to deal with due to the fuzzy requirements from which they are derived, the advantage of having early indicators of future software problems outweighs this inconvenience. We developed an approach for identifying requirements change risk factors as predictors of reliability and maintainability problems. Our case example consists of twenty-four Space Shuttle change requests, nineteen risk factors, and the associated failures and software metrics. The approach can be generalized to other domains with numerical results that would vary according to application.