This paper introduces an extension to the hypergraph data model used in the AutoMed data intergration approach that allows constraints common in static data modelling languages to be represented by a small set of primitive constraint operators. A set of equivalence rules are defined for this set of primitive constraint operators, and demonstrated to allow a mapping between relational, ER or UML models to be defined. The approach provides both a precise framework in which to compare data modelling languages, and forms the platform for further work in automating the process of transforming between different data modelling languages.