Data held in information systems is modelled using a variety of languages, where the choice of language may be decided by functional concerns as well as non-technical concerns. This chapter focuses on data modelling languages, and the challenges faced in mapping schemas in one data modelling language into another data modelling language. We review the ER, relational and UML modelling languages (the later being representative of object oriented programming languages), highlighting aspects of each modelling language that are not representable in the others. We describe how a nested hypergraph data model may be used as an underlying representation of data models, and hence present the differences between the modelling languages in a more precise manner. Finally, we propose a platform for the future building of an automated procedure for translating schemas from one modelling language to another.