There is a clear move towards the use of UML (Unified Modeling Language) models for the definition of standards applying to the electrical domain. This is true for the CIM (Common Information Model), and it will also soon be true for the IEC 61850 standard. There are clear advantages to the use of UML: this semi-formal language is an open standard supported by several tools and is quickly understood, at least its class diagram part used in the context of these IEC standards, by people even if they are not working in the software engineering domain. However, several XML (eXtensible Markup Language) based standards are derived from these UML based standards in particular to enable exchange of data. To validate such data, most tools work at the XML level. We will show why it is useful to put back data at the model level for validation or for other purposes.