In both semantic model standards Topic Maps and RDF/OWL and in many other NoSQL approaches to solve efficiently the problem of how to represent relations and relationships one major stumbling block is raised beyond all efforts: the namespace. It is a language problem, the babel we have in our civilized world is transferred into our IT systems. But machines do not have to understand our language, we do. The problem here is that from a semantic point of view, similar diagrams are in need from users that want to express business processes but when we reach the implementation stage software engineers have to marry business requirements with the technical constrains of the database system hence the ER diagram you see. Generally speaking this is known as "The Model", a conceptual view of the user on data. The ER version of the model has several limitations, due to the architecture of RDBMS.