http://hl7.org/fhir/StructureDefinition/elementdefinition-graphConstraint|5.2.0

Will cause a GraphDefinition to be executed and the referred-to instance be considered \"valid\" for that GraphDefinition if the instance is the start of a result of executing that GraphDefinition.
element_idtypes
Extension
Extension.extension
Extension.url
Extension.value[x]
Extension
Extension.id
Extension.extension
Extension.url
Extension.value[x]