Introduction

This IG defines the extensions that are globally defined and available in all FHIR implementation contexts. Prior to R5 these extensions were defined in the core specification, but starting from R5 they have been moved out of the specification into a separate extensions pack so that the extensions can be updated more often than the base specification. This extension pack also defines some search parameters for the extensions.

In addition, the extension pack also contains a series of mapping language scripts that provide a formal executable definition of the relationship between R5 and the prior versions R4 and R4B. These are located in the extension pack to allow them to also be updated as they are tested and used in production and improvements are made.

Content Registries

• ​Extension Registry
• ​Search Parameters for the Extensions
• ​R5/R4(B) Conversion Registry

Update Policy

Extensions

References to the extensions defined in this extension pack are found in Extension.url or in profile references to defined extensions in ElementDefinition.type.profile. While the profile references may be versioned using canonical versioned references, the most important references are in Extension.url and these are version-less.

For this reason, the extensions defined in this extension pack are managed very conservatively with regard to breaking changes:

• Extensions that are active are not subject to breaking changes. New extensions will be introduced if necessary
• Extensions labelled 'draft' may have breaking changes if the FHIR Management Group is satisfied that they are not in use in production, or if all the existing users are agree to making the change. The exact rules and processes still being discussed, but not all 'draft' extensions are subject to change
• In this regard, the definitions for breaking change to Normative artifacts apply. Note that the focus of these rules is preserving the validity and meaning of existing extensions, not preventing applications processing extensions from having to change
• The extensions all have the status of 'trial-use' but once they are active they are treated as normative. The FHIR Management Group has not yet decided how these extensions will be balloted in the future

Conversion Maps

The implementation scope of the conversion maps is fixed: implementing a proper transform from R4/R4B to R5 and vice versa. Ongoing changes may be made to the maps if they improve the mappings within this scope, including catering for common extensions.

Intellectual Property Considerations

This implementation guide and the underlying FHIR specification are licensed as public domain under the FHIR license. The license page also describes rules for the use of the FHIR name and logo.

This guide includes extensions making use of terminologies such as LOINC and SNOMED CT that have more restrictive licensing requirements. Implementers should make themselves familiar with licensing and any other constraints of terminologies used as part of their implementation process. In some cases, licensing requirements may limit the systems that data captured using certain codes may be shared with.

No use of external IP