Stream: conformance
Topic: Complex extensions reusing elements
Simone Heckmann (Aug 03 2018 at 08:43):
I have a complex extension with the elements A and B which are again complex having multiple sub-element
A A1 A2 A3 B B1 B2
Question: Can element A be an extension of B, so that I have
A
A1
A2
A3
B
B1
B2
A
A1
A2
A3
?
If so, how do I define that (with Forge)?
Michel Rutten (Aug 03 2018 at 09:38):
Hi @Simone Heckmann, interesting scenario. :wink:
In theory, you may be able to (ab)use the ElementDefinition.contentReference property:
Something like Extension.extension:B.extension:A.contentReference = "Extension.extension:A"
However:
- I'm not sure if derived profiles/extension definitions are allowed to introduce new contentReferences?
- I've never tested this in Forge, not sure if the tool supports this...
Lloyd McKenzie (Aug 03 2018 at 14:39):
I expect the IGPublisher and validator would blow up too...
Michel Rutten (Aug 03 2018 at 14:46):
@Lloyd McKenzie, is this even allowed by the spec?
Lloyd McKenzie (Aug 03 2018 at 20:14):
There's no prohibition against recursion in defining a complex extension.
Lloyd McKenzie (Aug 03 2018 at 20:14):
It's certainly not something explicitly contemplated or discussed, but technically it should be doable.
Simone Heckmann (Aug 13 2018 at 08:06):
IMO, this should work the same as with reusing Backbone-Elements, like we do with nested items in Questionnaire, for example.
...which is - I guess - what Michel is proposing.
Michel Rutten (Aug 13 2018 at 09:50):
Until now, I assumed that only core resource/datatype definitions (with StructureDefinition.derivation = specialization) are allowed to introduce a contentReference, to reduce complexity of the implementation. Interesting proposal however. Would you like to submit a gForge issue? i.e. also allow (complex) extension definitions to introduce a content reference.
Grahame Grieve (Aug 13 2018 at 10:33):
we have very specifically said, in r4, that only specialisations can use contentReference (after we considered all the truly confusing things you could do in a profile)
Michel Rutten (Aug 13 2018 at 11:04):
Phew... tool smith sigh of relief ;p
David Hay (Aug 13 2018 at 17:56):
Is deep nesting of complex extensions something to be encouraged? It kinda adds to the implementer complexity...
Lloyd McKenzie (Aug 13 2018 at 19:19):
Not encouraged. Deeper nesting than 2 levels should be unusual except possibly in Basic
Last updated: Apr 12 2022 at 19:14 UTC
