In its introduction, this article gives a short state of the art about ontologies of knowledge representation languages (KRLs) and the problems caused by i) the lack of relations between these ontologies, and ii) the lack of ontologies about notations (concrete syntaxes). For programmers, these are the difficulties of importing, exporting or translating between KRLs; for end-users, the difficulties of adapting, extending or mixing notations. To show how these problems can be solved, this article first shows how concepts of the main KRL standards can be aligned and organized. Then, it shows how this KRL model ontology can be re-used and completed by a notation ontology. Based on these two ontologies, KRLs models and notations - and thereby parsing and generation - can be specified in a concise way that even KRL end-users can adapt. The article gives representative examples. For these ontologies or specifications, a concise KRL notation is introduced and used. However, the presented approach is independent of any notation and model that has at least OWL-2 expressiveness. Thus, the results can easily be replicated. A Web address for the full specification of the two ontologies, and for a knowledge server to test or use them, is also given.