Object-Oriented Schema Extension and Abstraction

An algorithm is presented that abstracts out the "largest" common substructure of two given objectoriented class structures. This abstraction algorithm is based on two concepts: (1) a mathematical formulation of extension for class structures containing part-of and inheritance relationships, and (2) a definition of similarity on the class level. The algorithm shows how class structures can be optimized with respect to the extension relation, and how it can be used to abstract out a candidate parameterized class structure. The algorithm has been implemented as a schema transformation and design tool in the Demeter System