Potential limits to Complex Extensions

1

Hi All,
Is there a limit to the number of “levels” that a complex extension can have? For example the extensibility page has an example of an extension that has been extended. Something similar to this:

{
“resourceType”: “Patient”,
“extension”: [
{
“url”: “http://hl7.org/fhir/StructureDefinition/patient-citizenship”,
“extension”: [
{
“url”: “startDate”,
“valueDate”: “YYYY-MM-DD”
}
]
}
]
}

Are there any suggestions or limits for extending even further? Something like this with three “levels” of extensions:

{
“resourceType”: “Patient”,
“extension”: [
{
“url”: “http://hl7.org/fhir/StructureDefinition/patient-citizenship”,
“extension”: [
{
“url”: “period”,
“extension”: [
{
“url”: “startDate”,
“valueDate”: “YYYY-MM-DD”
},
{
“url”: “endDate”,
“valueDate”: “YYYY-MM-DD”
}
]
}
]
}
]
}

This example is not realistic, but it hopefully gets my point across. Thanks!

2

Nope. If you want to define an extension that’s 50 levels deep, you’d still be compliant. (But don’t count on an enthusiastic reception from any partners you ask to implement it… :>)

2 Likes
3

Just to add onto @lloyd s comment, its good to perhaps ask for a second opinion once your extension starts to look complicated, chances are there is a simpler way to present the same information.

1 Like
4

@lloyd @blessed_tabvirwa1 Sounds good, thank you both for the input!