Extension All FHIR elements must have a @value or children (inherited) Must have either extensions or value[x], not both (inherited) Extension.extension All FHIR elements must have a @value or children (inherited) Must have either extensions or value[x], not both (inherited) Extension.value[x] 1 All FHIR elements must have a @value or children (inherited) All FHIR elements must have a @value or children (inherited)