Variability models represent the common and variable features of products in a product line. Since the introduction of FODA in 1990, several variability modeling languages have been proposed in academia and industry, followed by hundreds of research papers on variability models and modeling. However, little is known about the practical use of such languages. We study the constructs, semantics, usage, and associated tools of two variability modeling languages, Kconfig and CDL, which are independently developed outside academia and used in large and significant software projects. We analyze 128 variability models found in 12 open--source projects using these languages. Our study 1) supports variability modeling research with empirical data on the real-world use of its flagship concepts. However, we 2) also provide requirements for concepts and mechanisms that are not commonly considered in academic techniques, and 3) challenge assumptions about size and complexity of variability models made in academic papers. These results are of interest to researchers working on variability modeling and analysis techniques and to designers of tools, such as feature dependency checkers and interactive product configurators.

Although bug reports are frequently consulted project assets, they are communication logs, by-products of bug resolution, and not artifacts created with the intent of being easy to follow. To facilitate bug report digestion, we propose a new, unsupervised, bug report summarization approach that estimates the attention a user would hypothetically give to different sentences in a bug report, when pressed with time. We pose three hypotheses on what makes a sentence relevant: discussing frequently discussed topics, being evaluated or assessed by other sentences, and keeping focused on the bug report's title and description. Our results suggest that our hypotheses are valid, since the summaries have as much as 12% improvement in standard summarization evaluation metrics compared to the previous approach. Our evaluation also asks developers to assess the quality and usefulness of the summaries created for bug reports they have worked on. Feedback from developers not only show the summaries are useful, but also point out important requirements for this, and any bug summarization approach, and indicates directions for future work.

Low bug report quality and human conflicts pose challenges to keep bug tracking systems productive. This work proposes to address these issues by applying game mechanisms to bug tracking systems. We investigate the use of game mechanisms in Stack Overflow, an online community organized to resolve computer programming related problems, for which the improvements we seek for bug tracking systems also turn out to be relevant. The results of our Stack Overflow investigation show that its game mechanisms could be used to address these issues by motivating contributors to increase contribution frequency and quality, by filtering useful contributions, and by creating an agile and dependable moderation system. We proceed by mapping these mechanisms to open-source bug tracking systems, and find that most benefits are applicable. Additionally, our results motivate tailoring a reward and reputation system and summarizing bug reports as future directions for increasing the benefits of game mechanisms in bug tracking systems.

Feature models describe the common and variable characteristics of a product line. Their advantages are well recognized in product line methods. Unfortunately, creating a feature model for an existing project is time-consuming and requires substantial effort from a modeler.

Variability models represent the common and variable features of products in a product line. Several variability modeling languages have been proposed in academia and industry; however, little is known about the practical use of such languages. We study and compare the constructs, semantics, usage and tools of two variability modeling languages, Kconfig and CDL. We provide empirical evidence for the real-world use of the concepts known from variability modeling research. Since variability models provide basis for automated tools (feature dependency checkers and product configurators), we believe that our findings will be of interest to variability modeling language and tool designers.