Concepts can be added to an extension, either to address content gaps or to expand the scope of SNOMED CT to include concepts that are used locally. Extension concepts are distributed in a concept file, which follows the standard RF2 release file format. For more details on the principles and processes for authoring concepts in an extension, please refer to 5.4.2 Authoring Concepts.
In addition to the four common attributes, extension concepts also have a definitionStatusId.
The definitionStatusId attribute specifies whether the concept is primitive or fully defined. If defining relationships are added, which sufficiently define the concept, then the definitionStatusId should be set to |Defined|. Otherwise, the extension concept is |Primative|.
Note that the attribute values in this row have been set according to the rules previously described.
Figure 188.8.131.52-1: A row from the concept table in the 20170901 US EditionPlease note the following: