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A core responsibility of an NRC is to make the International Edition of SNOMED CT and/or the National Extension of SNOMED CT available for Affiliates.
Every NRC must therefore be able to provide guidance on access to SNOMED CT, version control and management. Moreover, the NRC should be able to provide guidance to users on specific terminology services that are provided by the NRC, and in the use of national SNOMED CT developments, such as National Extensions, Reference sets, etc.
IHTSDO maintains and delivers shared content and derivatives

Footnote Macro
A SNOMED CT Derivative is a document, subset, set of maps, or other resource that consists of, includes, references or is derived from one or more SNOMED CT components . The standard computer processable representation for most types of SNOMED CT derivatives is a Reference set .

that provide the foundation of SNOMED CT. This is known as the SNOMED CT International Edition.
SNOMED CT is distributed as sets of files containing terminology components and derivatives. These release files contain the basic data needed to implement SNOMED CT in various modes in a technology-neutral formats. The format, content and names of the files delivered conform to SNOMED CT specifications and guidelines published in Section 5 of the Technical Implementation Guide (http://snomed.org/tig ).
Components represent the content of the terminology.
The standard SNOMED CT representation for content is as three interrelated files. The Concept file contains unique identifiers for clinical ideas, the Description file links human readable terms with identified concepts, and the Relationship file represents associations between identified concepts.
Derivatives facilitate the effective use of the terminology.
The standard SNOMED CT representation for derivatives is a consistent but flexible file format, known as the Reference set format. Reference sets can be used for a wide range of purposes including subsets, language preferences, ordered lists, hierarchies, annotations and mappings to or from other terminologies, classifications and code systems.

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