A Boolean Algebra Approach for Class Hierarchy Normalization

Normalization in object-oriented design is much different from that in relational database design. Not only are the conceptual data model of objectoriented (o-o) models integrating m’cher structuring capabilities than that of relational models, but also the dependency constraints, attribute ranges and access paths in o-o models are more complex than that in relational models. In o-o models, inheritance semantics is expressed mainly by class hierarchy, and it is important to ensure and maintain an appropriate class hierarchy. In this paper, we propose a Boolean algebra approach for class hierarchy normalization. A class hierarchy normal form(CHNF) and an indexing model for class hierarchy are defined respectively. Some methods and algorithms, such as transformation from a non-CHNF class hierarchy to a CHNF one, are given.