SNOMED CT Post Coordination in FHIR

If we can pass in a PCE then what does that mean?

The point of lookup is to get further information about a code - what further information could be gained .    Could we get a full decomposition.   We'd need to classify to then work out the parents and children, relationships that are inferred as part of that classification (may not be obvious from parentage due to presence of GCIs, etc)

We could say we expect validate-code to be called (or a subset of that functionality) as a matter of course to ensure the PCE is well formed and all component elements exist in the default / specified substrate.

Would we want to see logically generated display text (suggests we'd have to match a template to an expression, with a priority order).  The spec indicates that previously received text could be used.

"Validates that a coded value is in the code system"  and we say that PCE already exist in the CodeSystem - if all their component elements are valid and present.

Is close to user form acceptable?    Eg A disorder with both a body structure and a laterality attribute is considered "user form" and is a) contrary to the MRCM and b) not normalized ie we'd expect to see a body structure that is already lateralized.    A transformation can be performed to normalize the expression to make it correct.

What to do with inactive concepts used within an expression.   Validate code only checks that the code is in the system.  It does not consider inactive concepts to be invalid which suggests that a PCE that uses an inactive code should also be valid.  It would not classify in a meaningful way.    A structured response could be used to indicate to the calling code that a replacement (eg through historic association) should be sought.

Is there a way to indicate what we're doing with the concept in order to decide if MRCM validation should be performed or not.   We should assume that the context is one of 'end user' rather than authoring content.

Same issues as above in generating display text.

Additional out parameters can be used to give more detailed information about each component element.

Classification would need be performed and the resulting concept checked against the definition of the ValueSet 'contains' element to determine membership.   Filters may need to be applied.  

Note that validate-code would return true for a PCE that would NOT (by default) be included in the expansion of the same ValueSet since we don't return all PCEs by default.  Note that flag says if its valid to return these or not.  It is not requesting that they all be returned.

Valuesets tthat contain other ValueSets PLUS filtering conditions

PCEs in a CodeSystemSupplement that the ValueSet references.