What happened to the masterIdentifier?

Dear community,

I’m wondering what happened to the DocumentReference masterIdentifier in FHIR 5 and CI-Build documentation.
It think it is useful to have a version independent identifier for a document and a version dependent identifier, like the masterIdentifier was.
Someone knows why the newer definition of DocumentReference does not contain this identifier anymore?
What about mapping the XDS entryUUID and uniqueID of documents into the FHIR world without a masterIdentifier?
Can someone help?

Best wishes

The functionality that was in .masterIdentifier has been folded into .identifier. The distinction between business identifiers of the DocumentReference vs business identifiers of the object pointed to by DocumentReference was seen as unnecessary and presenting searching and discoverability problems.

There will be refinement of the Identifier.type done by IHE-MHD when IHE adjusts to a released FHIR R5.