Explaining software defects using topic models

Researchers have proposed various metrics based on measurable aspects of the source code entities (e.g., methods, classes, files, or modules) and the social structure of a software project in an effort to explain the relationships between software development and software defects. However, these metrics largely ignore the actual functionality, i.e., the conceptual concerns, of a software system, which are the main technical concepts that reflect the business logic or domain of the system. For instance, while lines of code may be a good general measure for defects, a large entity responsible for simple I/O tasks is likely to have fewer defects than a small entity responsible for complicated compiler implementation details. In this paper, we study the effect of conceptual concerns on code quality. We use a statistical topic modeling technique to approximate software concerns as topics; we then propose various metrics on these topics to help explain the defect-proneness (i.e., quality) of the entities. Paramount to our proposed metrics is that they take into account the defect history of each topic. Case studies on multiple versions of Mozilla Firefox, Eclipse, and Mylyn show that (i) some topics are much more defect-prone than others, (ii) defect-prone topics tend to remain so over time, and (iii) defect-prone topics provide additional explanatory power for code quality over existing structural and historical metrics.