Today I looked at the differences between FHIR R4 and R5.
There were a lot.
I couldn’t help but think of the upgrade price to be paid down the road. And how that upgrade price might not be evenly distributed.
First off, here’s the change log between the two versions: https://build.fhir.org/diff.html
It’s a fantastic document, clearly outlining the changes to each resource and to each element. The color coding makes it super easy to follow.
– Green for new elements
– Blue for moved or renamed elements
– Red for deleted elements and resources.
Let’s take Encounter as an example. It’s one of the most heavily used resources. If your app deals with Patients, you use Encounter!
So how did Encounter change, and what do those changes mean for your code?
– 7 new elements added. No code changes.
– 5 elements renamed. Minor code changes.
– 11 elements moved. Code and structural changes.
– 4 elements were deleted. Major changes.
Encounter got off lightly. Some resources were deleted entirely. Others had large sets of elements moved into new resources.
I don’t imagine a lot of projects will migrate from R4 to R5. But I do believe there will be a large migration from R4 to R6 in a few years.
And I expect the differences between R4 and R6 to be very large indeed.
So why did I say earlier that the upgrade price might not be evenly distributed?
I see two camps in the FHIR community.
One camp has essentially built their own FHIR server and API. For them changing from R4 might be straight forwards. A new API version, some data mapping and database changes and they’re good to go.
The other camp are using managed FHIR servers in the cloud — Azure, GCP, AWS and others.
They don’t have access to the underlying database, don’t control the API, and are fully reliant on the server and cloud provider.
Their only way to access their data is via the API. Even though they ‘own’ their FHIR server, they’re little more than a consumer with some elevated privileges.
If you’re in the second camp and you’re the enterprise architect for your product or a key business leader in your organization, you need to be very aware of this.
R6 will be here in a couple of years, and at that point the push to upgrade will start — possibly driven by regulatory changes.
You need to have your eyes on the horizon.
The R4 to R5 changes: https://build.fhir.org/diff.html
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