Extension 
url 
value[x] Documentation for this formatThis is the set of resources that conform to either of the profiles AllergyIntolerance Exposure Duration (http://hl7.org/fhir/StructureDefinition/openEHR-exposureDuration) and AllergyIntolerance Exposure Duration (http://hl7.org/fhir/StructureDefinition/openEHR-exposureDuration). 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 | Amount of time individual was exposed to Substance | ||
| url | 1..1 | uri | identifies the meaning of the extension | |
| value[x] | 1..1 | Duration | Value of extension | |
| Documentation for this format | ||||