It changes with each version, and it’s not backwards compatible. Your FHIR data model is NOT future proof.
The current release version is R5, but most of us use R4 and will continue to do so for some time.
We use resources that have disappeared in R5.
We create extensions and workflows to emulate resources that exist in R5 or might exist in R6.
We knowingly create data migration problems for the future.
My 2 cents: FHIR became too popular too soon.
Regulations like The Cures Act pushed it mainstream when normalization was and still is years away.
If you’re using R4, build for R4.
Use every resource and every element that R4 provides, regardless of the state of that resource in later versions.
Ignore R5 and discussions around R6. Don’t let future versions cloud your judgement when you’re building today’s data model.
There’ll be an upgrade price to pay regardless. Don’t start paying it before you have to.
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