HL7 Terminology (THO)
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HL7 Terminology (THO), published by HL7 International - Vocabulary Work Group. This guide is not an authorized publication; it is the continuous build for version 7.4.0 built by the FHIR (HL7® FHIR® Standard) CI Build. This version is based on the current content of https://github.com/HL7/UTG/ and changes regularly. See the Directory of published versions

Using BCP with HL7 Standards

This page describes how to use BCP 13 with HL7 Standards.

Using BCP 13 with FHIR R5

The BCP 13 code system represents the open namespace of media types defined by BCP 13. The code system includes syntactically valid media types regardless of whether they are registered in the IANA Media Types registry. IANA-registered media types form a subset of the code system.

Codes may also include media type parameters. Parameters form part of the code represented by this code system but do not form part of the media type registered by IANA.

Summary

SourceBCP 13 technical specification is managed by the Internet Engineering Task Force (IETF)
SystemThe URI urn:ietf:bcp:13 identifies the BCP 13 code system
VersionBCP 13 is not versioned like a traditional code system with discrete versioned releases. Accordingly, standardised version values are not defined. Version values SHALL therefore be omitted.
Code

A BCP 13 code is any syntactically valid media type, optionally including media type parameters, as defined by BCP 13 and applicable media type specifications. A code does not need to identify a media type registered in the IANA Media Types registry to be a valid code in this code system.

Media type names, subtype names, and parameter names are case-insensitive. Parameter values may be case-sensitive or case-insensitive, as specified by the definition of the applicable parameter.

DisplayThe correct display for a BCP 13 concept is the BCP 13 code itself.
InactiveAll BCP 13 concepts SHALL be assumed to be active. Media types registered in the IANA Media Types registry may be deprecated or obsoleted but remain registered and active.
Subsumption

A BCP 13 concept consisting of a media type without parameters subsumes concepts consisting of the same media type with one or more parameters.

For example, text/plain subsumes text/plain; charset=utf-8.

Implementers should note that the specification for a media type may define default parameter values that apply when a parameter is omitted. Such defaults may affect the subsumption relationship between codes with and without explicitly specified parameters.
Filter PropertiesSome filter properties are defined; see below.

Example Usage

  <coding>
    <system value="urn:ietf:bcp:13"/>
    <code value="application/fhir+xml"/>
    <display value="application/fhir+xml"/>
  </coding>

Copyright/License Issues

The full copyright statement and information about copyright, intellectual property, and licensing for BCP 13 and its constituent specifications, including RFC 4289, RFC 6838, and RFC 9694, can be found on the IETF's BCP 13 page.

BCP 13 Filter Properties

This specification defines two filters that may be used with the BCP 13 code system.

Name Operation(s) Value(s) Description
base = BCP 13 media type or partial media type, e.g. text, application/pdf, application/vnd.oasis.opendocument

Filters the code system based on the specified media type. The filter value may represent either a top-level type or a media type consisting of a type and subtype.

If the filter value specifies only a top-level type, all media types with that type are included. For example, base = text includes all media types with the text type.

If the filter value includes a subtype, the type and complete subtype must match. Additional subtype components introduced using . or a structured syntax suffix introduced using + are not implicitly matched.

For example:

  • base = application/fhir does not include application/fhir+xml; and
  • base = application/vnd.oasis.opendocument does not include application/vnd.oasis.opendocument.text

Media type parameters are not considered when applying this filter. Accordingly, base = application/fhir+xml includes both application/fhir+xml and parameterised forms of that media type.
registered = true

When true, restricts the code system to codes whose media type is registered in the IANA Media Types registry. Registration is determined from the media type without parameters.

The BCP 13 code system is not limited to IANA-registered media types. A syntactically valid media type may therefore be a valid BCP 13 code even when it does not satisfy the registered = true filter.

Note: The IANA Media Types registry registers media types identified by a top-level type and subtype. The subtype may incorporate a registration-tree prefix and/or structured syntax suffix. Parameters applicable to a registered media type may be specified by its registration or associated specification, but those parameters do not form part of the registered media type name.

Accordingly, when this filter is used with an operation of = and a value of true, registration is determined using the media type without any parameters. For example, if text/plain is registered, both text/plain and text/plain;charset=utf-8 satisfy the filter.

The registration status of a media type is independent of whether the media type has been deprecated or obsoleted. A media type that remains in the IANA Media Types registry satisfies this filter even when it is identified as deprecated or obsolete.

BCP 13 Implicit Value Sets

There are currently no general implicit value sets defined for the BCP 13 code system.