A new version of ISO 21127 (the ISO version of the CIDOC Conceptual Reference Model) is now available. ISO 21127:2014 A reference ontology for the interchange of cultural heritage information supersedes ISO 21127:2006.
The ISO publication is available in English and French and can be purchased online. The updated standard includes many revisions and corrections and a helpful diagrammatic representation of the ontology. It's based on version 5.0.4 of the CIDOC CRM.