http://terminology.hl7.org/CodeSystem/v2-0291|2.0.0

subtypeOfReferencedData

Code system of a subset of the media subtypes of binary data that are encoded in an ascii structure or stream. Used in Version 2 messaging ED and RP datatypes, but only in standard 2.5.1 and earlier; after that, it was recommended that the IANA media types be used instead of this short list of HL7-defined codes. More information on the standard media types and subtypes may be found at http://www.iana.org/assignments/media-types/media-types.xhtml.