This is the CodeSystem that contains all the codes in NCPDP Dispense As Written (DAW)/Product Selection Code (http://terminology.hl7.org/CodeSystem/NCPDPDispensedAsWrittenOrProductSelectionCode) and NCPDP Dispense As Written (DAW)/Product Selection Code (http://terminology.hl7.org/CodeSystem/NCPDPDispensedAsWrittenOrProductSelectionCode). E.g. what you have to deal with if you get resources containing codes in either of them