Scope note for the property same as external identifier (same as) – P20 Back
This property associates an entity, identified in the domain information system, with a persistent identifier provided for the same resource (be this physical or conceptual) in an external namespace i.e. in a different information system in which the entity receives an identifier (range of the property).
The nature of the external identifier (database primary key, authority file number, etc.) will be provided using specific types. In case of URIs, in the sense of the Semantic Web, the subproperty crm-sup:P28 same as URI [owl:sameAs] is to be preferred.