Stream: Profiling Academy
Topic: Required and Must Support
Linda (Dec 03 2019 at 20:55):
I have been reviewing the US Core Profiles and noticed there are times like in immunization with minimum cardinality is set to 1 (required) but it is also flagged with Must Support. What does that mean? I would think that Must Support would only be used when an item is NOT required but appreciate the explanation.
Richard Townley-O'Neill (Dec 03 2019 at 23:08):
A different example is date of death, this could be optional (0..1) and must support.
There is no requirement to send one, but if one is sent it must not be ignored.
Linda (Dec 04 2019 at 20:19):
That makes sense but what does Must Support mean on a Required field
John Moehrke (Dec 04 2019 at 20:37):
each IG must define what mustSupport means. US-Core defines it here https://www.hl7.org/fhir/us/core/general-guidance.html#must-support
Brett Marquard (Dec 20 2019 at 19:07):
We debated what made more sense -- a 1..1 with the must support flag, or without. It is redundant, but we decided it's less confusing to include.
Richard Townley-O'Neill (Dec 23 2019 at 00:38):
This is not US Core
We have profiles where a sliced element is 1..* and the base element is not must support, but some of the slices are 1..1 and must support.
For example https://github.com/AuDigitalHealth/ci-fhir-stu3/blob/master/output/SharedMedicinesList/StructureDefinition-composition-sml-prac-1.xml visible in https://github.com/AuDigitalHealth/ci-fhir-stu3/blob/master/output/SharedMedicinesList/full-ig.zip
Richard Townley-O'Neill (Dec 23 2019 at 00:46):
We have another example: List.mode where it is 1..1 and the only value that makes sense for our use is snapshot. As we have no interest in systems processing the value, we have fixed the value but not marked it must support. See https://github.com/AuDigitalHealth/ci-fhir-stu3/blob/master/output/SharedMedicinesList/StructureDefinition-list-sml-pracchanges-1.xml visible in https://github.com/AuDigitalHealth/ci-fhir-stu3/blob/master/output/SharedMedicinesList/full-ig.zip
Linda (Dec 26 2019 at 15:02):
I worry because I have talked to many people on this issue and I don't think it is consistently understood. The complexity is added because every IG defines their own "Must Support". I feel there are IG's where "Must Support" actually has stronger rules around it than "Required" in some guides. Perhaps that is ok just want to insure we are all on the same page.
Richard Townley-O'Neill (Jan 02 2020 at 03:06):
Yes, "Must Support" does confuse people. I think some of the reasons are that
- its meaning is defined in the implementation guide, not necessarily in the structure definition
- it is about system behaviour, not necessarily just data
Last updated: Apr 12 2022 at 19:14 UTC
