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FHIR R4 at Firely

Ardon Toonstra
Ardon Toonstra

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The FHIR R4 roadmap for the API, Simplifier, Forge and Vonk


Product Release Expected (2019) Release content
.NET API Alpha January R4 resources, FHIR client
Beta February  
Final April Snapshot generation, validation and bug fixes
Simplifier Alpha February R4 content upload to Simplifier
Beta March R4 rendering
Final May Snapshot generation and validation for R4 content 
Forge Final May Separate R4 release of Forge
Vonk 1.1.0 February Fixes and upgrade of the API
Final May R4 support


R4 is out – forget the ‘draft’ and ‘trial’

As you will all know by now: FHIR R4 has been published, containing – for the first time ever – normative content. In a narrow sense this means backward compatibility. No longer “Draft” in the name, or “Trial Use” – labels that tend to make executives nervous. In a broader sense, it will mean even further uptake for FHIR in the market.

Our policy for FHIR releases is that we start upgrading our product suite immediately after the official publication of the new release. No sooner, when the release is still a moving target; but certainly not later, because our users expect us to be aligned.

The pace of our releases is aligned with the HL7 Working Group Meetings. The next major release is the San Antonio release, early February 2019, which will contain some R4 features. The release after San Antonio is the Montreal release, May 2019. By that time, we will fully support R4, give or take some minor or corner-case features.

The San Antonio and Montreal release will contain many other features as well; that’s for another blog. This blog post focuses on R4 support.


All of our products rely on the official open source library for .NET. “Eat your own dog food.” We also know that thousands of apps out there rely on the .NET API.

Over the last months, many parts of .NET libraries are rewritten. Two major components, crucial for R4 support, are the snapshot generator and the validator. Both got an extensive facelift. In addition bug fixes, reported at the GitHub repo, have been solved. The API is more powerful, robust and reliable than ever. Just before the Working Group Meeting in San Antonio last week, a bottle of champagne was popped upon the alpha release of the FHIR .NET API.

This all with many thanks to the growing .NET FHIR community. The pull requests and bug reports are much appreciated. To facilitate the expanding community, the open stand-ups for the .NET API are streamed live to this YouTube channel. Shoot us an email if want to join the standups. needs to implement a great deal of the R4 .NET API as well. For example the snapshot generator that builds all those layered profiles for rendering and validation. Apart from the public .NET API, has an FHIR rendering library which needs to be upgraded to R4. Another important component is the file import functionality that will be rewritten and improved to handle all those different versions more easily.

We expect to be fully ready for R4 early May, so before the Montreal Working Group Meeting. Some R4 features will be released sooner as beta features. We will announce the release of early features through the Simplifier news channel. Create an account on Simplifier and you will be updated automatically.


Once the FHIR .NET API library has been fully updated to R4, we can start working on creating a new Forge application release for R4.

Updating the Forge user interface will require a bit of non-trivial work, as breaking changes in the ElementDefinition.type component and choice type constraints require us to redesign and re-implement the associated user interface components. Additionally, we have longstanding requests from the user community to improve the way element types are represented and managed in the Forge user interface. We will improve these parts of the user interface as well.

The Forge R4 release will be published as a separate install package that can be installed side-by-side with Forge for versions on the same machine. We expect to publish the initial Forge for R4 release is before the Montreal Working Group Meeting in May.


The R4 release of Vonk will support multiple FHIR versions within one instance. Vonk will handle requests based on the FHIR version in the content header or the specific FHIR version endpoint.

We plan to have Vonk R4 ready shortly before the Montreal Working Group Meeting, early May 2019. After this release, we might add DSTU2 support if there is a demand. If DSTU2 is a requirement for your use-case, send us an email.

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