Background The US Realm US Core Jurisdiction extension was added due to the change request FHIR-26943 , which the HL7 Financial Management Work Group reviewed before submitting it to US Core. US Core defines extensions that are US Realm defined and available in all US Realm FHIR implementation contexts, and It currently defines 2 extensions not included in any US Core profile. US Core Jurisdiction Extension US Core Direct email Extension Note that the FHIR Extensions Pack defines the extensions that are globally defined and available in all FHIR implementation contexts. Identifier.assigner (type Reference) is defined as the "Organization that issued/manages the identifier." with the comment: "The Identifier.assigner may omit the .reference element and only contain a .display element reflecting the name or other textual information about the assigning organization" In the datatypes page  it states: "The assigner is used to indicate what registry/state/facility/etc. assigned the identifier. As a Reference, the assigner can include just a text description in the display." Although an implementer may be able to infer the state jurisdiction from the assigned element, this is only sometimes the case. Example:   Regarding the comment: "Note that Device already has a jurisdiction (Included in .udiCarrier) which is not yet included in US Core and is actually explicitly a .uri data type." As stated above, this extension is US Realm defined and available in all US Realm FHIR implementation contexts, including Device resources that do not use UDI. Decision   Clarify that not all extensions are used in US Core Profiles by categorizing them and listing them as follows on the  Profiles and Extensions page : The following extensions are used US Core Profiles. The following extensions are not used in any US Core Profile. They are provided to assist implementers who may find them relevant to their specific use cases. The following extensions are ** only used in the US Core Profile StructureDefinition elements.