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20:00 UTC on Tuesday 25 August 2020 - 90 minutes.   


  • FHIR Terminology Services and Resources

Meeting Details


Phone: See for available phone numbers (meeting id 242-348-6949) # snomed-hl7-fhir (ask for invite!)

Zulip Chat:


 Rob HausamPeter G. WilliamsPeter JordanMichael LawleySander MertensSuzy Roy


Meeting Recording

Discussion items



OwnerNotes & Actions
1Welcome and introductions2

Recording, notes & attendance.

2Summary of previous week and previous fortnight5
3Other Meetings10

Upcoming events:

HL7 Baltimore Sept 19 - 25. Confirmed fully virtual event. Connectathon Sept 9 - 11 (two weeks earlier). HL7 Ballot currently active.

SI Business + Expo October Lisbon. Confirmed fully virtual event. SNOMED on FHIR Presentation + usual call on Tuesday 6 October.

FHIR North: Canada's FHIR Conference. October 14 15, 2020

November FHIRLY Dev Days expected - also virtual.

August Holidays - has more effect on the TB group? PW out 2 - 21 August - will pre-create all agenda.

4R4A Position15Rob Hausam

R4A probably not going to happen in the previously proposed form. More likely now to be an interim release of R5.

Continued discussion around the direction semantics for maps. Current state:

Update 14 July: Anticipating "R4B" release which is an initial release of R5.

11 August Uncertain when servers will take up R5 changes - e.g. ConceptMap updates.

Next Ontoserver release will include R4 and R5. May have "live endpoint" for testing these changes.
Is a "lossy" relationship translation from R4 to R5 acceptable, vs. an extension?
How is $translate output affected for "no map" based on the new element?

Uncertain when NZ will implement - will be using R4 for some time to come.

5Terminology Capabilities
Michael Lawley

Terminology Capabilities: Default SNOMED Edition for a Server. Suggestion to invite Graham for a wider discussion. Resource is still at maturity 0.

11 August The resource is based on instances of code systems. Difficult to make statements about code systems generally, or specific SNOMED editions, etc. Will start a Zulip discussion on this. Michael Lawley Then potentially invite Grahame for a future discussion?

25 August It has been agreed that this resource will now have maturity level 1

6New parameters proposed for streamlining operation of expand and validate code

7Post Coordination30Michael Lawley

Post coordination - primitive <<< syntax, what does this mean in practice, in context of use.

The problem is that, without FSNs, any two concepts with lexically identical structures must be assumed to be siblings because we can't detect equivalence. Eg two concepts both defined as <<< 64572001 |Disease (disorder)|

How do these behave with $subsumes (answer: you say they're not related) and $closure (trickier, you want to indicate that they're distinct but there are no identifiers to make this apparent).

Is this a case of - in practice - the client needing to check if an expression already exists and then making a decision if they can reuse that one, or need to create a new one. But given that we can't tell them apart without another identifier, how would that be useful. Upshot of this is that primitive PCEs are not terrible useful to use in an EHR. Use SD instead === the symbols here are optional and taken as the default when not present.

Could we make use of the display field in this situation? The end user will have some idea in mind when they create the expression. PCEs are often advertised as a way to allow existing/new medical concepts to be entered into systems at runtime.

TODO Discuss how should PCE Libraries be represented in FHIR? For example, do we include them in a ValueSet expansion? Surely yes, but possibly not by default. CodeSystem supplement?

8SNOMED Modules in FHIR20Rob Hausam

VSD - ValueSet Compliance discussion (targeting a profile), notion of code system partitions which seems to come from SNOMED having modules and this being seen as possibly useful. Could be expressed as Code System Fragments. ML "GPS is a good example of a useful SNOMED fragment / partition". Difficulties:

  • SNOMED is quite strict about module dependencies which would probably need to be represented if we wanted to split any given code system into 'partitions' .
  • In SNOMED modules we can describe things other than concepts - eg descriptions in one module and alternative modeling in another.
  • What version would I give for a fragment?
  • Modules are capable of inactivating components!

Modules exist for a small number of reasons: 1. To allow content to be developed by multiple parties, both in terms of decoupling and identifying ownership and 2. To keep SNOMED 'light' so that implementers only consider the modules that they need to. ML suggests not to equate a partition with a module.

11 August Reviewed our previous answer. A "partition" and a fragment are the same thing. The content of a a SNOMED module may correspond to a fragment, but not all fragments of SNOMED are modules. Fragments should have the same version as the entire code system.

9Preferred method to specify system/version - in url address or parameter10Daniel Karlsson

Either could be used in a GET request. In the CodeSystem endpoint, the Identifier (id) of Code system instance is somewhat arbitrary based on the server implementation, so the parameter approach is probably more transferable and quicker in that you don't need to look up anything first. URIs have been standardized.

  1. In the CodeSystem resource the URL containing the instance id eg http://localhost:8080/fhir/CodeSystem/sct_900000000000207008_20200309/$lookup?code=404684003 vs http://localhost:8080/fhir/CodeSystem/$lookup?system=

2. In ValueSet implicit expansion the use of a full URI in the url parameter to specify the code system version (saying version here is less confusing than 'instance' which might imply a CodeSystem object) vs doing that with the system-version parameter

eg http://localhost:8080/fhir/ValueSet/$expand?url=<<27624003

vs http://localhost:8080/fhir/ValueSet/$expand?url=<<27624003&system-version=

10$translate with version30

In the case of SNOMED, the system will as always be just

PWI advised that the crucial factor is the location of the map. The edition of the source and target is not important, so the use of the version parameter is prohibited. eg url=

ML says Ontoserver uses conceptMapVersion for this as well because concept maps that do not use a url in this way also need to be able to specify a version. Suggestion that the version parameter might be used if the conceptMapVersion is not specified.

11Publishing SNOMED codes in IGs and licencing conditions.

Licensing issues for IGs referring to SNOMED codes. Is this written down anywhere with some sort of rigour?

Consider the licence statement that is presented when accessing the browser. Should something similar be mandated for inclusion in any document published? What if a patient's medical record were to be published?

12Use of effective time parameter in $lookup15Michael Lawley

Suggestion that effectiveTime be added as a SNOMED specific property in the specification, raised by Peter Jordan in

The effective time of the concept (as represented in the concept file) does not necessarily capture when it came into its current state since relationships (inferred or stated) could change independently. Arguably we should use the most recent change to any of concept, relationships, descriptions. And what would we expect to happen in the case of filtering. ML: Ontoserver uses the date in the concept file because it's not possible to know what the enquirer's use case is.

Update 14 July: Recommendation of this group is that that item is added as a SNOMED specific property. Use case: In general, all properties should be filter-able. More specifically users may be interested to know which concepts were created (not perfect) or retired in the current release.

13Use of system and version parameters in Lookup and Subsumes15

Clarification that system parameter is the "class" of the code system and so is always in our case. The instance of the code system ie a specific extension and effectiveTime should be supplied in the version parameter. Snowstorm and Ontoserver are aligned in this regard.. In the case of SNOMED CT we use a URI to declare our instance and so the system is entirely redundant in our specific case and the decision was made to not insist in it's use for Snowstorm.$lookup?version=

DK: FSH apparently has no way of specifying the version of a CodeSystem. Daniel checking the ANTLR spec.


GPS and FHIR value set url(s)


  • Peter G. Williams follow up on GPS as a published reference set to allow for simple definition as a ValueSet using the memberOf operator. Answer: Yes we will do this when the GPS is next updated. TODO: Check publishing plans with Andrew Atkinson

11 August

This question still hasn't been fully answered. Suzy will review and report back. Suzy Roy

From Suzy: I can confirm that YES, the GPS will be published in RF2 format as a refset. 
That is in addition to the regular GPS flat file release.

15What module(s) to use for the Canadian Edition10Peter G. Williams
16Working with unversioned content15

Proposed example: http://localhost:8080/fhir/ValueSet/$expand?url=

ML makes the case that unpublished content is not legitimate SNOMED and suggested using a not-SNOMED URI eg in this case the code system would still be

Outstanding question: our pre-release (alpha + beta) packages do have a version as a future date in them, and continue to exist (although unpublished) even after the official release has shipped.

How would this look in a ValueSet expansion? Should we specify systemVersion or forceVersion in this case?

Update 2 June: LOINC have a similar issue with "Pre-release" identifiers - current release 2.6.7. Version 2.6.8PRE will contain the pre-release content. "To be useful they need to be considered part of the code system"

However in the case of SNOMED CT we would NOT condone unpublished identifiers being used in production systems. In the case of the COVID-19 concepts an interim release was done as an official release for 20200309. The use case here is for producers of SNOMED CT to reference concepts internally - as a work in progress.

11 August

Corrected the url listed above to the standard (not 'xsct'). Michael would still like to progress this. Needs further discussion in SNOMED Family of Languages group. Need for this is surfacing in Queensland Health.

17FHIR Roadmap5Peter JordanR5 being pushed back. GG seeking opinion on 4.1.0 - an opportunity to clean up some descriptions.
18FHIR Server Federation10

Use case for fall back lookup when server does not know the answer to any particular question eg a façade server which has knowledge of all services it could potentially delegate to.

Aug 25: New capabilities in HAPI to allow delegation to an external terminology server.

19Language Reference Sets in FHIR45All

Mechanisms for working with Languages

Designation extension

Update 19 May: Suggestion that we work an example for SNOMED to discuss with Regenstrief (LOINC)

Update 2 June: Started worked example Designation Extension Example

20SNOMED Family of Languages10

Impact of proposed changes (eg text searching in ECL) on FHIR. Questions around which language reference sets to use when there are multiple, especially partial/overriding context (referred to MAG for discussion)

21SNOMED FHIR Implementation Guide60

Implementation Guide for using SNOMED CT with FHIR.

Update 10 Dec: DK - main problem is URI/Ls which publisher has fixed ideas about. Publisher does not examine all folders - looks in profiles but not subfolders and doesn't seem to look in ValueSet folder.

Update 21 Jan: DK and RH have merged commits and these can be seen in the HL7 server build: and build errors here:

Update 11 Feb: Grahame said that he'd show us how to set the URI so that it doesn't have to follow the base URI. Next person to try that can we fire a Zulip off to ask about it?

Update 16 June: DK wondered about moving everything to FSH (FHIR Short Hand) as it's so much easier to maintain. ML: Conversion available, but round trip problematic. DK page Re: snowstorm FHIR requirements, issues, etc.

IG Documentation:

Also look at the sample IG see build


Any other business

Next time:

Potential Items for Discussion

OwnerNotes & Actions
API for FHIR Resource ↔ Post coordinated expression mapping

API for FHIR Resource to SNOMED Expression

  • Daniel Karlsson Thought there might be some documentation from CIMI on this. Also notes from DMarkwell about constructor bindings.
  • Peter G. Williams Pull these notes into confluence - can we mention it in the IG?
Looking up an SCTID in an unknown module

Problems when dependencies do not align. Multiple code system resources represent multiple editions / versions.

ML: See code parameter to code system search. Should return code systems (ie versions) where that code is defined. International concepts would appear in every edition known to the server.

eg /CodeSystem?system=htp://


See Discussion on Global Patient Set (GPS)
FHIR Shorthand
Michael Lawley


$lookup operation - properties returned
Peter Jordan

Using  I noticed that both Ontoserver and SnowStorm return a SNOMED CT $lookup property for effectiveTime, which I don't see listed, as one of the SNOMED CT properties in the FHIR R4 specification at Should we create a Jira TIcket to add this?

Completed -

Use of url parameter15

CodeSystem "class vs instance" in url parameter between CodeSystem and ValueSet operations.

CodeSystem is understood.

In Valueset, url is the ValueSet url for example url = allows for the version URI to be used as stated in The base URL is either , or the URI for the edition version, in the format specified by SNOMED International in the SNOMED CT URI Specification.

The ValueSet version valueSetVersion is just some string identifier eg a timestamp or 0.1.0

ECL in the Valueset Expression Extension10

Check whether SNOMED ECL is (or should be) registered as a MIME type (as per RFC 4289/BCP 13), or alternatively added to the expression-language code system and value set, for use in the valueset-expression extension used with the ValueSet resource.

For example, HL7 have registered application/json+fhir

This is useful for a ValueSet extension which allows any language to be used to define the selection criteria for an intensional definition using a MIME type. This group has no current reason to use that extension given the existing core specification support for implicit ValueSet definition and the support within the compose element.

RDF community may have an interest.

Update 2 June RH: Existing small valueset extended in BCP13 (existing known codes could be published as a CodeFragment). Vocab Working Group discussion ongoing.

Behaviour on Lookup10

What properties are returned?

Discussion: Both Ontoserver and Snowstorm are returning EffectiveTime which is not listed here (unlike other SNOMED specifics):

Point of interest: Grahame's server returns a copyright property.

Update 7 April - Question about whether this is required / desirable?

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