Metadata Hierarchy

As the release file formats contain a number of concept enumerations, it is necessary to define sets of concepts that represent the allowed values. As well as the enumerated values, other metadata supporting the extensibility mechanism and the concept model is required.
The concept $$ SNOMED CT Model Component (metadata) $$ is a subtype of the root concept ( $$ SNOMED CT Concept $$ ), and contains the metadata, supporting the release.
The subtypes of $$ SNOMED CT Model Component (metadata) $$ are described in and the top three levels of the hierarchy are shown in .

Table 15. SNOMED CT Model Component (metadata) (900000000000441003)
Id	Term	Comment
106237007	Linkage concept	Concepts that specify Semantic Relationships between concepts ( $$ Attribute $$ ); and Asserted associations between statements in a record ( $$ Link assertion $$ )
370136006	Namespace concept	Concepts that specify the Extension Namespaces allocated by the IHTSDO .
900000000000442005	Core metadata concept	Concepts that are referenced from enumerated fields within the International Release files (the Concept, Description, Relationship, Identifier files ).
900000000000454005	Foundation metadata concept	The metadata that supports the extensibility mechanism, and is discussed in more detail in the Reference Sets Guide .

Figure 2. SNOMED CT Metadata Hierarchy (2010-07-31)