My first few months working with FHIR I was afraid of extensions.
Everywhere I looked online FHIR experts complained about them.
- There are too many.
- There is no community involvement in creating them.
- Their casual use destroys interoperability.
- They’re not generic enough for re-use.
- And so on…
There’s truth in all of the above.
But it’s equally true that businesses and organizations are writing code today. They’re building products and solutions that have release dates weeks or months from now — not years.
There is often no time to put “community first” and to engage in wider discussion — not outside academia at least.
But that doesn’t mean casual extensions are the way to go.
If your project needs extensions — which most do — you can approach their creation responsibly by asking these 5 questions:
- Are you sure you need an extension?
- Does an extension already exist that meets the requirements?
- Is the use case for the extension likely to expand over time?
- Is there a need to run search queries on the extension values?
- Will the contents of the extension need to be validated?
I answered each of these questions in my very first FHIR Sessions email from last year. You can read it here:
Extensions are a polarizing subject. But they exist, they serve a purpose, and we have to live with them.
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