Data type categories in:
DRAFT HL7 Reference Information Model
RIM_Datatype_Generalizations
RIM_Datatypes
RIM_Datatypes_Demographic
RIM_Datatypes_Generic
RIM_Datatypes_Instances
RIM_Datatypes_Quantity
RIM_Datatypes_Text
RIM_Datatypes_Thing
RIM_Datatypes_Time