How Do Defects Hurt Qualities? An Empirical Study on Characterizing a Software Maintainability Ontology in Open Source Software

Beyond the functional requirements of a system, software maintainability is essential for project success. While there exists a large knowledge base of software maintainability, this knowledge is rarely used in open source software due to the large number of developers and inefficiency in identifying quality issues. To effectively utilize the current knowledge base in practice requires a deeper understanding of how problems associated with the different qualities arise and change over time. In this paper, we sample over 6000 real bugs found from several Mozilla products to examine how maintainability is expressed with subgroups of repairability and modifiability. Furthermore, we manually study how these qualities evolve as the products mature, what the root causes of the bugs are for each quality and the impact and dependency of each quality. Our results inform which areas should be focused on to ensure maintainability at different stages of the development and maintenance process.