NamingSystem — Address book of identifiers and codings
The registry of systems used in FHIR Identifiers and Codings: OID, URI, UUID, their owners, their descriptions, their synonyms.
Purpose of the resource
NamingSystem documents a system used to qualify an Identifier (e.g.
urn:oid:1.2.250.1.213.1.4.8 for France's INS-NIR) or a Coding (e.g.
http://loinc.org). It declares the owner, the type (code system or identifier
system), the known UniqueIds (OID, URI, UUID, other), and their preference.
It plays a critical role in the national ecosystem: the French OID registry, HL7 International's OID Registry, IHE PIX, all publish their data as NamingSystems.
Key fields
| Field | Type | Cardinality | Role |
|---|---|---|---|
url | uri | 0..1 | Canonical URL. |
identifier | Identifier[] | 0..* | Business identifiers. |
version | string | 0..1 | Version. |
name | string | 1..1 | Short name. |
title | string | 0..1 | Human-readable title. |
status | code | 1..1 | draft | active | retired | unknown. |
kind | code | 1..1 | codesystem | identifier | root. |
date | dateTime | 1..1 | Registration date. |
publisher | string | 0..1 | Publisher. |
responsible | string | 0..1 | Operationally responsible entity. |
type | CodeableConcept | 0..1 | Identifier type (HL7 v2-0203 or local). |
description | markdown | 0..1 | Description. |
usage | string | 0..1 | Usage context description. |
uniqueId | BackboneElement[] | 1..* | Known unique identifiers (OID, URI, UUID, other). Has a preferred. |
JSON example
{
"resourceType": "NamingSystem",
"id": "loinc",
"name": "LOINC",
"status": "active",
"kind": "codesystem",
"date": "2026-05-15",
"publisher": "Regenstrief Institute",
"responsible": "Regenstrief Institute, Inc.",
"type": {
"coding": [{
"system": "http://terminology.hl7.org/CodeSystem/v2-0203",
"code": "LN"
}]
},
"description": "Logical Observation Identifiers Names and Codes — observation identifiers.",
"usage": "LOINC is used to identify laboratory observations and clinical measurements.",
"uniqueId": [{
"type": "oid",
"value": "2.16.840.1.113883.6.1",
"preferred": false
}, {
"type": "uri",
"value": "http://loinc.org",
"preferred": true
}]
}Common pitfalls
- No
preferred=true— leaves consumers puzzled. - Non-normalised OID — always store without prefix (the
urn:oid:prefix is added on use). - Mixing identifier / codesystem — a code system and an identifier system are not declared the same way.
Related resources
- CodeSystem — code system.
- ValueSet.
- ConceptMap.
- TerminologyCapabilities.
- FHIR R5 hub.