Data Modeling in UML and ORM: A Comparison

The Unified Modeling Language (UML) is becoming widely used for software and database modeling, and has been accepted by the Object Management Group as a standard language for object-oriented analysis and design. For data modeling purposes, UML includes class diagrams, that may be annotated with expressions in a textual constraint language. Although facilitating the transition to object-oriented code, UML’s implementation concerns render it less suitable for developing and validating a conceptual model with domain experts. This defect can be remedied by using a fact-oriented approach for the conceptual modeling, from which UML class diagrams may be derived. ObjectRole Modeling (ORM) is currently the most popular fact-oriented approach to data modeling. This paper examines the relative strengths and weaknesses of ORM and UML for data modeling, and indicates how models in one notation can be translated into the other.