Extension 
extension 
url 
value[x] Documentation for this formatThis is the set of resources that conform to either of the profiles Period of validity of the catalog (http://hl7.org/fhir/uv/order-catalog/StructureDefinition/ValidityPeriod) and Period of validity of the Composition (for Order Catalog profiles) (http://hl7.org/fhir/uv/order-catalog/StructureDefinition/ValidityPeriod). E.g. what you have to deal with if you get resources conforming to one of them
| Name | Flags | Card. | Type | Description & Constraints Filter: |
|---|---|---|---|---|
| Extension | 0..1 | Validity Period | ||
| extension | 0..* | Extension | Additional content defined by implementations | |
| url | 1..1 | uri | identifies the meaning of the extension | |
| value[x] | 1..1 | Period | Value of extension | |
| Documentation for this format | ||||