Conceptual entropy and its effect on class hierarchies

All systems that undergo frequent change characteristically tend toward disorder. This is known as entropy and is recognized in all branches of science. Class hierarchies are shared structures which, if useful, undergo frequent change in the form of additional subclassing, modification to existing classes, and sometimes the restructuring of the hierarchy itself. Given this frequent change, we can expect class hierarchies to exhibit entropic tendencies, which we term conceptual entropy. Conceptual entropy is manifested by increasing conceptual inconsistency as we travel down the hierarchy. That is, the deeper the level of the hierarchy, the greater the probability that a subclass will not consistently extend and/or specialize the concept of its superclass. Constructing and maintaining consistent class hierarchies is one of the most difficult activities of object-oriented design. The article describes an automated classification tool that helps minimize conceptual entropy.<>