As part of our proposal for adding IRI stems to LOINC in terminology.hl7.org (THO), the RDF for Semantic Interoperability subgroup would like to propose adding a new NamingSystem identifier type for IRI stems. This would allow us to identify uniqueIds in NamingSystem definitions that specify an IRI stem. NamingSystem.uniqueId only has a single field that can be used to specify the type of the value and this `type` field is a required, non-extensible valueset, so only this field can be used to specify that the value is an IRI stem. You can see a fuller description of the problem at https://jira.hl7.org/browse/UP-364.

This would require a new code to be added to `codesystem-namingsystem-identifier-type.xml` at https://github.com/HL7/fhir/blob/6e4833c36833a0c7bbd2ff9ff0206a1e05492dca/source/namingsystem/codesystem-namingsystem-identifier-type.xml with the following values:

• code: iri-stem
• display: IRI stem
• definition: An IRI string that can be prepended to the code to obtain a concept IRI for RDF applications. This should be a valid, absolute IRI as defined in RFC 3987. See https://build.fhir.org/rdf.html#iri-stem for details on how this value may be used.