Optional_Optional_Literal reference, Relative, internal or absolute URL
Optional_Type the reference refers to (e.g. "Patient")
OptionaldisplayText alternative for the resource
OptionalextensionAdditional content defined by implementations
OptionalidUnique id for inter-element referencing
OptionalidentifierLogical reference, when literal reference is not known
OptionalreferenceLiteral reference, Relative, internal or absolute URL
OptionaltypeType the reference refers to (e.g. "Patient")
Text alternative for the resource