[[wikipedia:Code_refactoring]] is only useful when one has access to the overall codebase that needs to be refactored. It comes with no surprise that in the area of [[APIDesign]] where one design an [[API]] for a framework, but doesn't control its usages, that is hardly the case. As such [[refactoring]] externally visible parts of an [[API]] isn't really a [[good]] idea when one cares about [[BackwardCompatibility]].