What the ids a recording system passes as Request::resource are, which
decides how entity:data names the data a read, create, update or delete
accessed.
FHIR R4 Reference.reference holds a location a FHIR server resolves, a
relative [type]/[id] or an absolute URL, and Reference.identifier
names an object no FHIR server makes available (references.html
§2.3.0.2, §2.3.0.3). The record writes no other value as a reference, so
an id that is no literal reference is an identifier whatever is declared.
Non-exhaustive enums could have additional variants added in future. Therefore, when matching against variants of non-exhaustive enums, an extra wildcard arm must be added to account for any future variants.
The ids are literal references to the FHIR resources the recording
system serves, written as what.reference. An id that is no literal
reference (ihe_atna::balp::is_literal_reference) is written as
what.identifier with no system.