With time, the set of concepts, or other components, referenced in a reference set will need to change, either because of changes in SNOMED CT, changes in clinical knowledge, or changes dictated by errors or omissions in the original reference set. The original reference set will have been given an identifier that is used to reference the reference set in models or other entities that use that particular reference set. When a change is required that maintains the original intent but updates the content, the change is considered a new version of the reference set. Versioning maintains the reference set identifier and additional reference set attributes.
Following topics will be presented in relation to reference set maintenance: