Empirical evaluation of reliability improvement in an evolving software product line

Reliability is important to software product-line developers since many product lines require reliable operation. It is typically assumed that as a software product line matures, its reliability improves. Since post-deployment failures impact reliability, we study this claim on an open-source software product line, Eclipse. We investigate the failure trend of common components (reused across all products), highreuse variation components (reused in five or six products) and low-reuse variation components (reused in one or two products) as Eclipse evolves. We also study how much the common and variation components change over time both in terms of addition of new files and modification of existing files. Quantitative results from mining and analysis of the Eclipse bug and release repositories show that as the product line evolves, fewer serious failures occur in components implementing commonality, and that these components also exhibit less change over time. These results were roughly as expected. However, contrary to expectation, components implementing variations, even when reused in five or more products, continue to evolve fairly rapidly. Perhaps as a result, the number of severe failures in variation components shows no uniform pattern of decrease over time. The paper describes and discusses this and related results.