codesystemId
The URI that uniquely identifies a code system, expressed as a string literal. Typically a FHIR canonical URL such as 'http://snomed.info/sct'.
Examples
SNOMED CT system URI
codesystem "SNOMED-CT": 'http://snomed.info/sct'
LOINC system URI
codesystem "LOINC": 'http://loinc.org'
ICD-10-CM system URI
codesystem "ICD-10-CM": 'http://hl7.org/fhir/sid/icd-10-cm'
EBNF
codesystemId : STRING ;