Concept enumerations are used across all release files. A concept enumeration simply uses concepts in a metadata hierarchy to represent an enumerated value set rather than using arbitrary Integer values directly. A concept enumeration therefore uses an SCTID data type.
Non-clinical metadata is separated from the SNOMED CT clinical content by holding the two types of data in two separate hierarchies. The concept named 900000000000441003 |SNOMED CT Model Component|, which is a child of the root concept 138875005 |SNOMED CT Concept|, contains the metadata model that supports each release.
Underneath the 900000000000441003 |SNOMED CT Model Component| hierarchy, the 900000000000442005 |core metadata concept| sub-hierarchy contains concepts that are referenced from fields within other International Release files (the Concept, Description, Relationship).
The 900000000000454005 |foundation metadata concept| sub-hierarchy also sits below the 900000000000441003 |SNOMED CT Model Component| hierarchy. This sub-hierarchy contains the metadata that supports the extensibility mechanism, and is discussed in more detail in the Reference Sets Guide.
The third and forth sub-hierarchy under 900000000000441003 |SNOMED CT Model Component| are the 106237007 |linkage concept| sub-hierarchy, which holds details of relationship types, and the 370136006 |namespace concept| sub-hierarchy, which holds details of Namespaces.
For more information, see 4.1 Concept enumerations .