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The purpose of this page is to outline the process by which an HL7 community member shall engage an external code system owner for information regarding the external code system's use within HL7 products. 

Engagement Process

  1. HL7 Community Member (Requestor) identifies the need for the use of an external code system within an HL7 product
  2. Requestor does due diligence - searching of existing code system information (e.g., Uniform Terminology Governance RepositoryFHIR Codesystem Registry, OID Registry, FHIR Community Codesystem Registry, HTA External Terminologies Registry) PRIOR to contacting HTA for assistance
  3. Requestor initiates request by:
    1. Opening a ticket via the HL7 HQ dedicated tracking system - currently use the HTA JIRA Project (Preferred Method as (b) will result in a JIRA ticket also)
    2. Contacting HTA via an email to the open HTA listserv or the closed HTA members only listerv depending on sensitivity of the content (e.g., proprietary content or sensitive information).
  4. HTA will review request and confirm that the external code system has not priorly been utilized in HL7 artifacts and/or Code system information (name, owner etc) and identifiers (URI, OID etc) are not available
    1. HTA will notify the HL7 community of the request via Implementers and Terminology Zulip channels
    2. HTA will provide the requestor with a temporary URI using the following syntax
  5. HTA will work with the requestor to gather all pertinent information for the request
  6. HTA will send the Initial Request Letter to the Code System owner, copying the Requestor where appropriate
  7. If a response is received by HTA within the stated timeframe, HTA will
    1. Proceed with resolving the request, collaborating with the Requestor and Code System owner
    2. HTA will notify, if applicable, the HL7 Unified Terminology Governance facilitator
    3. Send the Collaborative Follow-up Letter documenting the mutual decisions made
  8. If a response is NOT received by the HTA within the stated timeframe. HTA will:
    1. Work with the requestor and other required parties (e.g., if applicable, the "HL7 Unified Terminology Governance facilitator"- an HL7 dedicated resource who undertakes the maintenance of content in the UTG) to create the required Code System Information for use within HL7 products.
      1. If creating a new URI, HTA will use a standard syntax ( where the xxx is an established (at HL7 OID site or other) short symbolic name.
        1. (Note, that HL7 publishing tools require that the xxx not contain an additional / as everything after "CodeSystem/" is used as the ID)
    2. Send the Follow-Up Letter notifying the Code System owner of the decisions made by HL7
  9. Upon resolution, HTA will close any open tickets, attaching pertinent correspondence and documenting the resolution. Steps include
    1. Creation of an informational page under External Terminologies - Information
    2. Notify requestor and/or known interested parties
    3. Notify the HL7 community of the resolution via Implementers and Terminology Zulip channels
    4. Notify the Vocabulary Work Group

Related Information

Proposed Vocabulary WG Policy on Creation of Canonical URLs for Code Systems in THO


The following templates shall be used within the process

Initial Request Letter

Collaborative Follow-Up Letter

Follow-Up Letter

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  1. I think this is good, but should acknowledge that many actual agreements may require SOUs developed by HQ (Karen) with CTO and approved by the Board Executive Committee.  

  2. Wayne - sounds good, but what would be the criteria that would require a Statement of Understanding to be put in place?

    Should reference the possibility of setting up an SOU but not in the initial letter.  Is likely to be case by case - and possibly at the request of the code system owner / HQ.

  3. FWIW, this is a recent real-world request that might (should) be a trigger for this process:

    Wondering if there is an existing ValueSet/CodingSystem that captures the HTTP response codes. The closest I found was, but the intent of these codes isn't quite the same as representing the response codes themselves (and is also incomplete, e.g. 401). Would prefer not to create a new ValueSet/CodeSystem if there is an existing one.


    Is there an established URN for , the same way we have for IETF or ISO codes?

  4. Thanks Michael - this one came to me this morning too from someone else - so I can tell it's a live issue.  (smile)

  5. I have another set of needed code system identifiers - This is for the SANER project. They need to have code system identifiers for Dartmouth Atlas region codes as mentioned here: W. Boonehas contacted the help desk but of course gotten no response. I suggest we assign for these where xxx is PCSA, HSA, and HRR. The main page for the atlas is and seems to be where we can get the data for each of these code systems (although its honestly a bit unclear.) lists Kathy Stroffolino as the primary contact. 

    1. Thanks Rob, I have contacted Kathy Stroffolino. Ted Klein and Joshua Procious are working on adding a workflow to the UTG Jira project to support these requests. When that is ready, this will be moved over there so you can follow the progress of the request.

  6. Updated the policy with communication items 4.a and 9.c, as agreed on the 7/8 joint call with Vocab and CTO

  7. Hello Julie James Caroline Macumber one of the links in item 2 of Engagement process above is broken.  The FHIR Community Codesystem Registry) link resolves to an error