@techreport {KroeherSchmid17b,
author={Christian Kröher and Klaus Schmid},
title={A Commit-Based Analysis of Software Product Line Evolution: Two Case Studies},
organization={University of Hildesheim},
institution={Software Systems Engineering, Institut für Informatik, Universität Hildesheim},
number={2/2017, SSE 2/17/E},
year={2017},
pages={1-57},
url={https://sse.uni-hildesheim.de/media/fb4/informatik/AG_SSE/PDFs/publications/SPL-Evolution/TR-Evolution.pdf},
abstract={Software Product Line (SPL) evolution affects a variety of artifact types, each containing their artifact-specific information as well as variability information. While the former information type defines the basic content of an artifact, like the general program definition in code artifacts, the latter supports the customization of these artifacts for different products of the SPL. Existing work that aims at characterizing the state and evolution of a product line identifies general SPL evolution scenarios or evaluates the (co-)evolution of variability information in different types of artifacts. However, these results are typically based on a feature perspective, which abstracts from the SPL evolution at large. We argue that an artifact-based analysis of product line evolution will complement existing work by analyzing the intensity of changes to different artifact and information types. In this report, we therefore present an approach for and the results of the extraction and analysis of changes introduced to artifact-specific and variability information in code, build and variability model artifacts. This approach has been developed for and applied to the Linux kernel. In order to broaden our analysis, we also apply the approach to the Coreboot firmware. The results reveal the intensity of changes over the evolution history of both SPLs. Further, we compare the intensity of changes across both SPLs with respect to the size of the changes as well as over time.}
}