Why (not) ORM?

The two widely used approaches to data modelling, the application of Unified Modelling Language (UML) and Object Role Modelling (ORM) are compared. Since one of the purposes of modelling is to present and clarify the system design, the key comparison criteria were expressivity, i.e., clear presentation and easy perception of the stored information and substantiality, i.e., ability to store lots of information. A few characteristic situations were chosen that frequently arise in data modelling practice, and the examples clearly show how the same information can be very differently perceptive in ORM and UML models. Thus, the paper can help in selection of the modelling framework for a particular project