Managing Hidden Dependencies in OO Software: a Study Based on Open Source Projects

Dependency-based software change impact analysis is the domain concerned with estimating sets of artifacts impacted by a change to a related artifact. Research has shown that analysing the various class dependency types independently will not reveal a complete estimate of impact sets. Therefore, dependency types are combined to improve the precision of estimated when compared to impact sets. Software classes can be linked in different ways; for instance semantically, if their meaning is somewhat related or, structurally, if one class depends on the services of other classes. 'Hidden' dependencies arise when two classes, linked structurally, do not share the same semantic namespace or when semantically dependent classes do not share a structural link. With the goal of revealing hidden dependencies during change impact analysis, we empirically investigated the interplay between structural and semantic class dependencies in object-oriented software systems. Results show that (i) semantic and structural links are significantly associated, (ii) the strengths of those links does not play a significant role and, (iii) a significant number of dependencies are hidden. We propose refactoring techniques to deal with hidden dependencies, based on existing design patterns. Our approach has the potential for reducing refactoring and testing effort.