The ontology file includes @prefix crm: <http://www.cidoc-crm.org/cidoc-crm/> . but no resource from CRM is referenced. The Nomisma ontology should be mapped to CRM as discussed here. Do you prefer to have this mapping been made outside of Nomisma or as official part? In the end it's "just" (famous last word) adding rdfs:subClassOf and rdfs:subPropertyOf to every class/property.