extension shown: fhir [x]

DocumentReference.masterIdentifier

Defined in the fhir.schema.org extension.
Canonical URL: http://schema.org/DocumentReference.masterIdentifier

Thing > Property > DocumentReference.masterIdentifier

Document identifier as assigned by the source of the document. This identifier is specific to this version of the document. This unique identifier may be used elsewhere to identify this version of the document.

Usage: Fewer than 10 domains
Values expected to be one of these types
Identifier
Used on these types
DocumentReference

Schema Version 2.2