There's a large number of `context` options provided in `DocumentReference.context`, including "event", "period", "facilityType", and "practiceSetting" (probably too many options). But there's no clear way to link a DocumentReference to the encounter that its document is documenting.

In theory, `DocumentReference.context.related.ref` could be used this way to point to an Encounter, but sthe desired semantics aren't clear ("this document is documenting this encounter"), and this kind of catch-all reference is a troubling pattern because it will lead to proliferation of incompatible modeling choices.

(If `context.related` does remain, I'd recommend changing it to `related[x]` with allowed types of `Reference` and `Identifier`. But I'd rather just see more specific relations defined.)

(Note that if the structures do survive, I'd at least like to see the name `ref` changed to avoid the abbreviation.)