Predicting the order of fault-prone modules in legacy software

A goal of software quality modeling is to recommend modules for reliability enhancement early enough to prevent poor quality. Reliability improvement techniques include more rigorous design and code reviews and more extensive testing. This paper introduces the concept of module-order models for guiding software reliability enhancement and provides an empirical case study that shows how such models can be used. A module-order model predicts the rank-order of modules according to a quantitative quality factor. The case study examined a large legacy telecommunications system. We found that the amount of new and changed code due to the development of a release can be a better predictor of code churn due to subsequent bug fixes, compared to software product metrics alone. In such projects, process-related measures derived from configuration management data may be adequate for software quality modeling, without resorting to software product measurement tools and expertise