Property codeSystem : WideString; (Read/Write)
The code system that defines the code, or if no code was found, the codeSystem in which no code was found.
Code systems SHALL be referred to by a UID, which allows unambiguous reference to standard code systems and other local codesystems. Where either ISO or HL7 have assigned UID to code Systems, then these UIDs SHALL be used. Otherwise implementations SHALL use an appropriate ISO Object Identifier (OID) or UUID to construct a globally unique local coding system identifier.
A CD that has a code attribute SHALL have a codeSystem specifying the system of concepts that defines the code.
An CD with a nullFlavor OTH indicates that a concept could not be coded in the coding system or value set specified. Thus, for these coding exceptions, the code system or value set that did not contain the appropriate concept SHALL be provided in codeSystem or valueSet.