Metaschemas for ER, ORM and UML Data Models
Terry Halpin · Journal of Database Management · 2002
This paper provides metaschemas for some of the main database modeling notations used in industry. Two Entity Relationship (ER) notations (Information Engineering, and Barker) are examined in detail, as well as Object Role Modeling (ORM) conceptual schema diagrams. The discussion of optionality, cardinality and multiplicity is widened to include Unified Modeling Language (UML) class diagrams. Issues addressed in the metamodel analysis include the normalization impact of non-derived constraints on derived associations, the influence of orthogonality on language transparency, and trade-offs between simplicity and expressibility. To facilitate comparision, the same modeling notation is used to display each metaschema. For this purpose, ORM is used because of its greater expressibility and clarity.