Source:http://linkedlifedata.com/resource/umls/id/C1555721
HL7V3.0: <p>Definition: Indicates that the subject Act has undergone or should undergo substitution of a type indicated by Act.code.</p><p>Rationale: Used to specify "allowed" substitution when creating orders, "actual" susbstitution when sending events, as well as the reason for the substitution and who was responsible for it.</p>