http://hl7.org/fhir/StructureDefinition/id|5.0.0

id type: Any combination of letters, numerals, \"-\" and \".\", with a length limit of 64 characters. (This might be an integer, an unprefixed OID, UUID or any other identifier pattern that meets these constraints.) Ids are case-insensitive.
{description: 'id type: Any combination of letters, numerals, \"-\" and \".\", with a length limit of 64 characters.  (This might be an integer, an unprefixed OID, UUID or any other identifier pattern that meets these constraints.)  Ids are case-insensitive.', derivation: specialization, name: id, type: id, class: primitive-type, kind: primitive-type, url: 'http://hl7.org/fhir/StructureDefinition/id', base: 'http://hl7.org/fhir/StructureDefinition/string', version: 5.0.0}