An integrated process and product model

The relationship between product quality and process capability and maturity has been recognized as a major issue in software engineering based on the premise that improvements in process will lead to higher quality products. To this end, we have been investigating an important facet of process capability, stability, as defined and evaluated by trend, change, and shape metrics, across releases and within a release. Our integration of product and process measurement and evaluation serves the dual purpose of using metrics to assess and predict reliability and risk and concurrently using these metrics for process stability evaluation. We use the NASA Space Shuttle flight software to illustrate our approach.