Do crosscutting concerns cause modularity problems?

Abstract

It has been claimed that crosscutting concerns are pervasive and problematic, leading to difficulties in program comprehension, evolution, and long-term design degradation. To consider whether this theory bears out, we examine the patch history of the Mozilla project over a period of a decade to consider whether crosscutting concerns exist therein and whether we can see evidence of problems arising from them. Mozilla is an interesting case, due to its longevity; size; polylingual nature; and use of a patch review process, which maintains strong connections between issue reports and the patches that are intended to address each. We perform several statistical analyses of the over 200,000 patches submitted to address over 90,000 issues reported in this time period. We find that 90% of patches show little or no evidence of scattering, that the scattering of a patch tends to decrease slightly upon review on average, and that the system shows at worst a slow increase of average scattering over time.