A first-order logic expression of the CIDOC Conceptual Reference Model

The CRM is specified in a semantic data modelling style and relies on consolidated notions for the representation of knowledge such as classes, properties, IsA hierachies, domain and range constraints and cardinality restrictions. These notions are considered sufficiently clear and unambiguous both in the documentation and in the standardization communities. The CRM specification has been used several times for implementing the model, and some of these implementations support large knoweldge bases, such as the one at the British Museum. The status of the CRM as a data definition language is therefore quite solid, from a practical point of view.