In this paper, we present a taxonomy that allows the maintainer to catalog OO classes based on the characteristics of the class. The characteristics of a class include the properties of data items and methods, as well as the relationships with other classes in the application. We construct a tool to track changes across multiple releases of software applications containing hundreds of classes, providing information about each changed class. Our tool identifies class changes in terms of the characteristics exhibited by classes with the same name in different releases of an application.