UK Core Profiling Approach

This is a copy of the documentation used by the UK Core development team to produce the initial UK Core Implementation Guide and UK Core FHIR assets. As such it is written as guidance for UK Core development team members to create FHIR assets and therefore uses language for that audience and may refer to items which are not in the public domain at present. It is draft and will be updated and matured inline with the C&TA process. It is aimed at the technical reader and is included as reference material. This is based on the UK Core Design Principles.

Introduction

This is an internal document intended to assist with the development of FHIR profiles for the FHIR R4 UK Core implementation guide (UK Core) and is intended for:

• Technical Modellers in the Interoperability Specifications team (IOPS)
• New members joining the UK Core project, for example from NHS Wales.

The UK Core is ‘a collection of FHIR resources designed to increase the ability of health information systems within the NHS to work together within and across organisational boundaries in order to advance the effective delivery of healthcare for individuals and communities.’
This document details the approach to take when producing initial FHIR profiles for the UK Core. This is before any technical and clinical assurance for these FHIR profiles takes place.

General profiling approach

Where this document refers to FHIR assets, this includes:

• StructureDefinitions
• ValueSets
• CodeSystems
• ConceptMaps

For each new FHIR asset you will need to refer to the existing FHIR STU3 CareConnect asset, if there is one published on the HL7 FHIR Reference Server, and develop a UK Core equivalent.

Snapshot component

The snapshot component must be included when developing profiles in Forge. This setting can be selected from the Options menu.

Enforced structures

Referring to the existing FHIR STU3 CareConnect asset will help you to identify enforced structures that will need to be applied to the new UK Core profile. If a CareConnect profile does not exist, this section will not apply to the new UK Core profile. An enforced structure in a FHIR profile is where an element has been sliced, and either one or both of the following conditions apply:

• fixed values have been applied to child elements (such as the system element)
• a terminology binding has been applied

Uplift from FHIR STU3 to FHIR R4

If you are referring to an existing CareConnect profile as part of your development work, you will also need to refer to an Impact Assessment Output spreadsheet. The Impact Assessment Output spreadsheet details the impact of the FHIR R4 specification on the existing CareConnect profile. The files are held on the Confluence CareConnect R4 Uplift page. Where a FHIR element is impacted by a change in the FHIR R4 specification, you will need to seek input from the UK Core Technical Lead on the correct modelling approach.

Properties

This section details how to constrain the properties for FHIR assets.

Common properties

URL Prefix The URL prefix to be applied to all FHIR assets is https://fhir.hl7.org.uk/*

*This is currently under review by the UK FHIR Delivery Senior Leadership Team and may change.

StructureDefinition properties

For StructureDefinition properties which identify the FHIR profile, the following patterns apply:

• id: UKCore-[resource] – this is also the physical filename for the StructureDefinition
• uri: https://fhir.hl7.org.uk/StructureDefinition/UKCore-[resource]
• name: UKCore[resource]
• title: UK Core [resource]

For StructureDefinition properties which identify the FHIR extension, the following patterns apply:

• id: Extension-UKCore-[name] – this is also the physical filename for the Extension
• uri: https://fhir.hl7.org.uk/StructureDefinition/Extension-UKCore-[name]
• name: ExtensionUKCore[name]
• title: Extension UK Core [name]

Example

Using the Patient resource as an example, the patterns for the full set of StructureDefinition properties are demonstrated here:

• id: UKCore-Patient
• version: 1.0.0
• uri: https://fhir.hl7.org.uk/StructureDefinition/UKCore-Patient
• name: UKCorePatient
• lifecycle status: draft
• title: UK Core Patient
• copyright: Copyright © 2020 HL7 UK Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except in compliance with the License. You may obtain a copy of the License at http://www.apache.org/licenses/LICENSE-2.0 Unless required by applicable law or agreed to in writing, software distributed under the License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the License for the specific language governing permissions and limitations under the License. HL7® FHIR® standard Copyright © 2011+ HL7 The HL7® FHIR® standard is used under the FHIR license. You may obtain a copy of the FHIR license at https://www.hl7.org/fhir/license.html.
• publisher: HL7 UK
• contact information:
  • name: HL7 UK
  • system: email
  • value: secretariat@hl7.org.uk
  • use: work
  • rank: 1
• contact information:
  • name: NHS Digital
  • system: email
  • value: interoperabilityteam@nhs.net
  • use: work
  • rank: 2
• purpose: This is as documented in Profile-Descriptions-Purposes, or provided by a Technical Lead.*
• description: This is as documented in Profile-Descriptions-Purposes, or provided by a Technical Lead.*

*This text will also be added to the implementation guide page for the Profile in the UK Core IG.

Properties for ValueSets, CodeSystems and ConceptMaps

Filename format The physical filename format to be used for these assets is as below:

• ValueSets: ValueSet-UKCore-[Name]
• CodeSystems: CodeSystem-UKCore-[Name]
• ConceptMaps: ConceptMap-UKCore-[Name]

url property The url format to be used for these assets is as below:

• ValueSets: https://fhir.hl7.org.uk/ValueSet/UKCore-[Name]
• CodeSystems: https://fhir.hl7.org.uk/CodeSystem/UKCore-[Name]
• ConceptMaps: https://fhir.hl7.org.uk/ConceptMap/UKCore-[Name]

Common properties

• id: UKCore-[Name]
• name: UKCore[Name]
• title: UK Core [Name] – remember to use spaces between words
• status: draft – unless stated otherwise

Copyright, publisher and contact information – ValueSets and ConceptMaps

The copyright, publisher and contact information to be used for ValueSets and ConceptMaps is as below:

• copyright: Copyright © 2020 HL7 UK Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except in compliance with the License. You may obtain a copy of the License at http://www.apache.org/licenses/LICENSE-2.0 Unless required by applicable law or agreed to in writing, software distributed under the License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the License for the specific language governing permissions and limitations under the License. HL7® FHIR® standard Copyright © 2011+ HL7 The HL7® FHIR® standard is used under the FHIR license. You may obtain a copy of the FHIR license at https://www.hl7.org/fhir/license.html.
• publisher: HL7 UK
• contact information:
  • name: HL7 UK
  • system: email
  • value: secretariat@hl7.org.uk
  • use: work
  • rank: 1
• contact information:
  • name: NHS Digital
  • system: email
  • value: interoperabilityteam@nhs.net
  • use: work
  • rank: 2

Copyright, publisher and contact information – CodeSystems

By default, all CodeSystems will use the following copyright, publisher and contact information:

• copyright: Copyright © 2020 NHS Digital
• publisher: NHS Digital
• contact information:
  • name: NHS Digital
  • system: email
  • value: interoperabilityteam@nhs.net
  • use – work

This may change if a different copyright owner, publisher and contact is identified in CodeSystem requirements.

Extensions

There is a UK Core requirement to develop extensions based on the equivalent CareConnect extensions. The exception to this is where an extension is no longer needed, as it has been developed in the FHIR R4 Specification. For CareConnect profiles these exceptions will have been documented in the relevant Impact Assessment Output spreadsheet. Extensions will not be constrained (hard Coded) into profiles. The only exception will be where an extension has been previously applied in order to enforce structure, for example Extension-NHSNumberVerificationStatus. The Implementation Guide for the UK Core will include an Extension Library page, which will list extensions for use with the FHIR profiles. Once the approach above has been applied, it will need to be reviewed against the Extension Design page in the UK Core Development Guidance.

HL7 Extensions

There is no requirement to profile HL7 extensions locally. Where a HL7 extension is identified as in scope, you will need to add a link to it on the Extension Library page under HL7 Common Extensions.

Versioning

Internal versioning for FHIR assets will use the pattern demonstrated for the version element in Properties, i.e. version: 1.0.0 Implementation Guide Versioning has yet to be confirmed. Provisionally the Implementation Guide will use a description, for example ‘November 2019’.

Terminology bindings

The CareConnect profiles have terminology bindings applied inconsistently. This section will clarify how to apply terminology bindings in UK Core profiles, based on what is discovered in the terminology bindings that have been applied in the CareConnect profiles. Terminology bindings in a CareConnect profile will need to be recreated in the UK Core profile, with the following conditions:

• the terminology binding strength must be set to ‘Extensible’
• no cardinalities are applied to the system, code and display elements A current exception to this approach is the terminology binding applied in the UKCore Extension NHSNumberVerificationStatus, where the binding strength for the valueCodeableConcept is set to Required. This is due to a business requirement which is currently being reviewed, so this binding strength may change.

ValueSets referring to more than one CodeSystem

Some CareConnect ValueSets include codes from more than one CodeSystem. Examples include CareConnect-AllergyCode and CareConnect-AllergyManifestation. These ValueSets include codes from SNOMED CT and HL7. However, in the CareConnect profile they have been bound to sliced coding elements with the label ‘snomedCT’. This is incorrect profiling. These ValueSets will need to be bound to the FHIR element without slicing the coding element – see Sliced coding elements with no fixed system element for an example.

Terminology bindings in the FHIR R4 base profile

There may be cases where an element in the FHIR R4 base profile is already bound to a ValueSet with a binding strength of ‘Required’ or ‘Extensible’, for example Patient.gender or Patient.maritalStatus. In this case the FHIR R4 profile must remain unchanged and any terminology binding found in the CareConnect profile must not be carried forward. Note: the profiling approach to terminology bindings in sliced coding elements will differ, refer to the Slicing section for this guidance.

Coding.system – fixed values

Fixed values in the coding.system element are not to be applied.

Binding strength	Coding.system element
FHIR Required	Retain base profiling
UK Core Required	No fixed value as the UK Core should not use the Required binding strength. Current known exception is NHS Number Status Indicator, which is to be reviewed during technical and clinical assurance.
Extensible	No fixed value
Preferred	Binding strength currently not in use by UK Core, but no fixed value
Example	Binding strength currently not in use by UK Core, but no fixed value

ConceptMaps

As stated above, the base terminology binding to a FHIR Required ValueSet must remain unchanged. However, a ConceptMap may have been profiled for a CareConnect profile which needs retaining for the UK Core.

With the use of Simplifier, the profiling approach for ConceptMaps in FHIR R4 is not the same as the approach you will have used for developing CareConnect profiles. To develop a ConceptMap:

• create your UK Core ValueSet (for example ‘UK Core Person Stated Gender Code’)
• create a ConceptMap which maps your UK Core ValueSet to the FHIR ValueSet (for example UK Core Person Stated Gender Code and MaritalStatus). Existing ConceptMaps which have used this approach can be viewed on Simplifier, for example AdministrativeGender. For previous ValueSet bindings where the system element has been fixed (e.g. to SNOMED CT) and there is a reference to a ValueSet, this is an enforced structure. You will need to recreate this terminology binding in the UK Core profile, but apply the ‘Extensible’ binding strength.

SNOMED CT expression checking

Where a ValueSet includes a SNOMED CT ECL expression, this expression will need to be validated as instructed on the Confluence page SNOMED ECL Statements.

Approach to StructureDefinition elements

Cardinality

Element cardinalities will remain unchanged from the base FHIR resource, so you will not need to apply any cardinalities.

Identifiers

Where existing FHIR STU3 profiles have applied slicing and profiling to identifiers, you will need to recreate these in the UK Core profiles. This will be for demonstration purposes only.

Slicing

Slicing will only be used where it enforces structure, such as a ValueSet binding or representation of an identifier. You will need to apply the following constraints when slicing elements:

• set the Slicing ‘Rules’ property to ‘Open’
• where the ‘Is ordered’ property is set to ‘true’, set the slicing ‘Rules’ property to ‘OpenAtEnd’
• where slicing is applied to a coding element:
  • apply 1..1 cardinalities to the system, code and display elements
  • apply the discriminator properties as below*:
    • Type = value
    • Path = system

*Following Uk Core development team discussion, this is a temporary decision until the full profiling options for slicing discriminators for coding elements have been explored.

MustSupport labelling

The MustSupport property in StructureDefinitions will not be used for the UK Core profiles, so you will not need to apply this label.

Removal of elements

No elements will be removed from the FHIR assets for the UK Core profiles, so you will not need to profile any elements out.

Design Decisions

identifier.assigner in reference elements

For elements of reference datatype, the identifier.assigner should reference the UK Core Organization profile.	But ‘identifier.assigner’ is a nested element, and if the UK-Core-Organization profile is referenced, the Forge tool will create additional nesting for profiling

The interim approach is to not apply further profiling in this new nested structure and leave as per the base profile.

Sliced coding elements with no fixed system element

The Care Connect AllergyIntolerance profile has the following profiling applied to the code element:

• the coding element was sliced
• a ‘snomedCT’ slice was created, where the following profiling was applied:
  • the system value was not fixed to http://snomed.info/sct
  • a terminology binding to a ValueSet AllergyCode was applied, however this ValueSet includes codes from two different CodeSystems (SNOMED CT and HL7)

In this scenario, the terminology binding has been applied to the AllergyIntolerance.code element in the FHIR R4 profile as described in Terminology bindings in the FHIR R4 base profile. This is the approach to be taken where this scenario appears, but you must seek input from the Technical Lead to confirm.

'StructureDefinition.experimental' in FHIR profile metadata

The FHIR specification defines the ‘experimental’ element as the following, when set to ‘true’: 'This structure was authored for testing purposes (or education/evaluation/marketing), and is not intended for genuine usage.' Source: http://hl7.org/fhir/structuredefinition.html Currently there is no requirement in the UK Core to set the experimental element as ‘true’ or ‘false’, so this field should remain in the default view (undefined).