Advance Care Planning composition profile - missing constraints on elements with a Reference

[dtr-agency]

Prerequisites

• [X] I have searched open and closed issues to make sure it isn't already requested or reported
• [X] I have written a descriptive issue title

The issue / feature

Change description

The Advance Care Planning Composition is missing constraints on elements with a logical type of Reference.

Without a constraint on Reference there is a wide range of values that are accepted as passing validation, some of which are undesirable. For example,

• the Composition.subject element has the References constrained to profiles that enforce a Patient.identifier - it is intended the subject always has an identifier.
• if no further constraint is placed on Reference then a subject with only a display or an extension is allowed - more permissible than we intend.

Add constraints on Composition elements of type Reference where additional constraints are desired for the use case:

This is expected to be:

• constraining the cardinality of each Composition.section.entry.reference to be 1..1
• Adding invariants at the Composition element for:
  • Composition.subject to enforce a reference or an identifier with a system and a value
  • Composition.author to enforce a reference or an identifier with a system and a value
  • Composition.custodian to enforce a reference or an identifier with a system and a value
  • Composition.attester.party to enforce a reference or an identifier with a system and a value

What it actually enables people to do

Enables consistent implementation and validation of meaningful data that serves the use case. Provides clarification of how to support the expected usage scenarios.

Mockups

Not available.

How awesome would it be?

Highly desirable - the design is incomplete without these constraints. This issue must addressed at some stage prior to release for implementation.

Workarounds

This missing design feature may be addressed in the STU3 profile by documentation of a known issue rather than adding invariants to the Composition. Or possibly a mix of both, addition of some invariants / constraints and a known issue covering off the other invariants not included in the STU3 profile. Example known issue content

Reference	Description	Issue No.
subject	The design of this element is incomplete. In the future it is intended subject shall be constrained to at least have a reference or an identifier with at least a system and a value.	See ci-fhir-stu3/issues/63
attester.party	The design of this element is incomplete. In the future it is intended party.Reference shall be constrained to at least have a reference or an identifier with at least a system and a value.	See ci-fhir-stu3/issues/63

...

Additional context

composition-sml-prac-1 is an example of a Composition with these constraints in place including functioning FHIRPath expression.

[SatyaYelisetti]

Work is in progress to add invariants to cater for the design features of elements subject and attester.party.

[SatyaYelisetti]

The invariants for both the elements have now been added and are out for review.

[SatyaYelisetti]

Changes to the FHIRpath can now be found in the above commit of the structure definition.