FHIR Assets

This section documents the approach used by the UK Core Development team to produce and maintain the UK Core Implementation Guides and the UK Core FHIR assets. It will be updated and matured in line with decisions taken during the Clinical and Technical Assurance process. This documentation is aimed at the technical reader and is included as reference material. The approach is based on the design principles.

Conformance

The UK Core conforms to the HL7 FHIR® specification (Release 4) and its assets are profiles of the corresponding base HL7 FHIR resources.

Further information about conformance in FHIR is available.

Design Principle

Key Principle:

FHIR assets must not be England specific and must be capable of representing the requirements of each UK nation identified during collaboration.

Other Principles

Extensions

There is a UK Core requirement to develop extensions based on any equivalent CareConnect STU3 extensions. The exception to this is where an extension is no longer needed because either

  • the data can be carried in a new element for a relevant resource in FHIR R4
  • a corresponding common extension has been developed in FHIR R4

Extension will be constrained (hard coded) into profiles to profiles after agreement during Clinical and Technical assurance.

The Implementation Guide for the UK Core will include an Extension Library page, which will list extensions and their corresponding UK Core profiles. There is no requirement to profile HL7 extensions locally. Where a HL7 extension is identified as in scope, a link to it will be added on the Extension Library page under HL7 Common Extensions.

Read more about FHIR Extensions and Extension design.

Cardinalities

  • "FHIR resource element cardinalities will only be amended, if clinical justifications are agreed during Clinical and Technical assurance."
  • "No elements will be removed unless deemed clinically unsafe following consultation and agreement during Clinical and Technical assurance."

Read more about FHIR resource cardinalities.

Slicing

  • "Must only be used where it enforces structure in a profile", for example
    • for a ValueSet binding
    • for the representation of an identifier in a list, such as a patient's NHS number
  • "Slicing must be Open e.g. one or more additional slices can be added."

Read more about Slicing in FHIR.

Must Support

  • "Will only be used when there is a requirement arising from a use case identified during Clinical and Technical assurance."

Read more about "Must Support" in FHIR.

ValueSets

  • Binding strength SHOULD be set to 'extensible', where not defined as 'required' by the FHIR standard.
  • If the ValueSet contains SNOMED CT or dm+d concepts, then the binding strength SHOULD be set as 'preferred'.
  • For all other ValueSets, 'required' or 'preferred' binding strengths for ValueSets should only be used, if agreed during collaboration." The binding strength should be decided as part of the Clinical and Technical Assurance process.
    no mention of example strength

Read more about ValueSets and ValueSet bindings in FHIR.