Data Model Equivalence

Abstract

The current proliferation of proposals for database system data models and the desire for database systems which support several different data models raise many questions concerning "equivalence properties" of different data models. To answer these questions, one first needs clear definitions of the concepts under discussion. This paper presents formal definitions of the terms database, operation, operation type, application model and data model. Using this formal framework, database state equivalence, operation equivalence, application model equivalence and data model equivalence are distinguished. Three types of application and data model equivalence are defined - isomorphic, composed operation and state dependent. Possiblities for partial equivalences are mentioned. Implementation implications of these different equivalences are discussed. Examples are presented using two semantic data models, the semantic relation data model and the semantic graph data model.