Gaining higher level evolutionary information about large software systems is a key in validating past and adjusting future development processes. In this paper, we analyze the proximity of software features based on modification and problem report data that capture the system's evolution history. Features are instrumented and tracked, the relationships of modification and problem reports to these features are established, and the tracked features are visualized to illustrate their otherwise hidden dependencies. Our approach uncovers these hidden relationships between features via problem report analysis and presents them in easy-to-evaluate visual form. Particular feature dependencies then can be selected to assess the feature evolution by zooming in into an arbitrary level of detail. Such visualization of interwoven features, therefore, can indicate locations of design erosion in the architectural evolution of a software system. Our approach has been validated using the large open source software project of Mozilla and its bug reporting system Bugzilla.
