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Simplify modelling of 'CodedWithExtensions' CWE pattern of DV_CODED_TEXT by addition of an 'unbounded' qualifier to defining_code constraint

Description

I think it is now pretty clear that it would be helpful to have the
equivalent of a CNE/CWE attribute applied to a DV_CODED text
constraint. This is a very common clinical modelling pattern, where we
want to define an internal valueset or referenced termset, but wish to
allow other terms to be used if required. We will, of course often
wish to tighten this constraint at template level.

Although we can simulate this requirement by the use of a
DV_TEXT/DV_CODED_TEXT element, this is pretty messy and unintuitive to
model and I think we should strongly consider in ADL1.5, the addition
of an 'unbounded' attribute to DV_CODED_TEXT, defaulting to
False. I think it would have to be this rather than LimitToList to
provide backwards compatibility but it may make sense to default to
true for new DV_CODED_TEXT elements in archetype tooling.

After discussion with Thomas Beale, one option might be to allow a simple qualifier to be appended to the coded text constraint.

e.g.

ELEMENT[at0005] occurrences matches {0..1} matches { – Rhythm
value matches {
DV_CODED_TEXT matches {
defining_code matches {
[local::
at0006, – Regular
at0007, – Irregular
*] – Any other coded_text
}
}
}
}

This is considerably simpler to model and understand than a DV_TEXT/DV_CODED_TEXT pair, is aligned closely to the HL7 CNE/CWE vocabulary strength and is also explicit that only another coded_text is allowed, not free text. It could also be applied to a term-binding constraint, where the binding offered is not mandatory and any other coded_text is allowed. This would allow 'open' access to a terminology without this having to be explicitly modelled in every termset.

Environment

None

Change Description

None

Impact Analysis

None

Status

Assignee

Unassigned

Reporter

Ian McNicoll

Components

Affects versions

AM version 1.4

Priority

Major