A new method is presented for analyzing and reengineering class hierarchies. In our approach, a class hierarchy is processed along with a set of applications that use it, and a fine-grained analysis of the access and subtype relationships between objects, variables and class members is performed. The result of this analysis is again a class hierarchy, which is guaranteed to be behaviorally equivalent to the original hierarchy, but in which each object only contains the members that are required. Our method is semantically well-founded in concept analysis: the new class hierarchy is a minimal and maximally factorized concept lattice that reflects the access and subtype relationships between variables, objects and class members. The method is primarily intended as a tool for finding imperfections in the design of class hierarchies, and can be used as the basis for tools that largely automate the process of reengineering such hierarchies. The method can also be used as a space-optimizing source-to-source transformation that removes redundant fields from objects. A prototype implementation for Java has been constructed, and used to conduct several case studies. Our results demonstrate that the method can provide valuable insights into the usage of the class hierarchy in a specific context, and lead to useful restructuring proposals.

Object-oriented applications may contain data members that can be removed from the application without affecting program behavior. Such "dead" data members may occur due to unused functionality in class libraries, or due to the programmer losing track of member usage as the application changes over time. We present a simple and efficient algorithm for detecting dead data members in C++ applications. This algorithm has been implemented using a prototype version of the IBM VisualAge C++ compiler, and applied to a number of realistic benchmark programs ranging from 600 to 58,000 lines of code. For the non-trivial benchmarks, we found that up to 27.3% of the data members in the benchmarks are dead (average 12.5%), and that up to 11.6% of the object space of these applications may be occupied by dead data members at run-time (average 4.4%). 1 Introduction Object-oriented applications may contain data members (instance variables) that can be removed from the application without affecting p...