Restructuring Object-Oriented Database Schemata by Concept Analysis

Abstract

Different reasons may require to restructure an existing database schema. For instance, restructuring can improve the comprehensibility of a schema. For relational databases there is the relational normalization theory which provides a means of avoiding redundant storage of data. Normalization is based on a notion of equivalence for database schemata. At the time being, there are only very few comparable approaches to normalizing object-oriented databases. In this article we present an approach to transforming class hierarchies in object-oriented database schemata into a "normal form". For this transformation we first have to perform an extensional analysis which provides the necessary information about extensional relationships among the classes in a given schema. Then, we apply the framework of formal concept analysis in order to derive a "normalized" class hierarchy.