http://hl7.org/fhir/StructureDefinition/id|4.0.1

Base StructureDefinition for 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.
NameFlagsCardTypeDescription & Constraints
id
0..*Primitive Type id
 
value
0..1http://hl7.org/fhirpath/System.StringPrimitive value for id