The RDF for Semantic Interoperability subgroup of the HL7 ITS work group has been working with the Terminology Services Management Group to incorporate IRI stems into CodeSystem and NamingSystem resources on the HL7 Terminology website (see minutes). Adding IRI stems to CodeSystems is straightforward, since Identifier.type is defined as a CodeableConcept; we therefore only need to create a new code to identify IRI stems. Adding IRI stems to NamingSystems is more complicated: IRI stems should be placed in the NamingSystem.uniqueId field, but to do this we need to choose a type for the (required) NamingSystem.uniqueId.type field. The values for this type must be from the NamingSystem Identifier Type codeset.

Internationalized Resource Identifiers (IRIs) are an extension to URIs to allow them to include Unicode characters that were defined by the Internet Engineering Task Force (IETF) in 2005, and which has been widely used since then in a number of applications, including web browsers and RDF datasets. An example IRI would be https://hi.wikipedia.org/wiki/हृदय. Many software tools, including many browsers, can resolve them by percent-encoding them into a URI as described in RFC 3987, section 3.1 (for example, this IRI would translate to the URI https://hi.wikipedia.org/wiki/%E0%A4%B9%E0%A5%83%E0%A4%A6%E0%A4%AF). While we could implement IRI stems by using the existing "other" type, adding an "iri" type would require minimal changes to the FHIR specification but would allow for a richer set of unique identifiers for NamingSystems.

We therefore propose adding the following concept to the NamingSystem Identifier Type codesystem:

• Code: iri
• Display: IRI
• Definition: An Internationalized Resource Identifier (IRI), which extends the syntax of URIs to support Unicode characters. Defined by RFC 3987, which includes an algorithm for converting IRIs into URIs. e.g. https://hi.wikipedia.org/wiki/हृदय