SNOMED CT® Release Format 1 (RF1) Guide - ihtsdo

• Local content requirements that are likely to have wider applicability should be submitted to a National
Release Center for consideration.
• National requirements likely to have International value should be submitted to the IHTSDO so they can
be considered for inclusion in the International Edition.
2.1.3.2. Practical uses of Extensions
An Extension mechanism offers many advantages to developers, vendors, terminologists, national bodies
and users.
Such a mechanism allows:
• Users to access the SNOMED CT International Release and one or more Extensions through a single
user interface;
• Developers to implement SNOMED CT Extensions without developing specialized software;
• Vendors to develop and sell products to take advantage of both International Release content and
Extensions;
• Organizations to develop and share terminology that meet their business needs, without procuring
software;
• IHTSDO Affiliates to develop terminology that can be shared with other organizations and considered
for addition to the International Release content;
• IHTSDO Affiliates to use locally-developed terminology without potential overlap with the work of other
organizations .
This structure also enables specialized Concepts and Descriptions within an Extension to be related to
Concepts and Descriptions distributed as part of SNOMED CT.
• An Extension Concept may be:
• A national or organizational definition of a concept, which is more rigorous or specific than that generally
applied to the SNOMED CT Concept;
• An experimental procedure that is not established sufficiently to merit the inclusion in the main body
of SNOMED CT but which may be in a local controlled study.
• Extension Descriptions may be colloquial synonyms for a SNOMED CT Concept or descriptions for an
Extension Concept.
• Extension Relationships may be required to allow analysis packages or decision-support protocols to
access additional information about a SNOMED CT Concept or to describe relationships between Extension
Concepts:
• Links between local procedures and relevant administrative actions;
• Links between local procedures and SNOMED CT Procedures.
• Extension Subsets may group SNOMED CT Concepts in ways that are specific to data entry contexts of
a particular application or communication specification.
The Concepts, Descriptions, Relationship and Subsets that form an Extension must be:
• Distinguishable from the main body of SNOMED CT, not only in the thesaurus, but also when stored in a
patient record, query or decision support protocol;
• Distinguishable from other Extensions, in the same way as they are distinguishable from the main body
of SNOMED CT;
• Able to be distributed and processed in the same way as equivalent components from the main body of
SNOMED CT without requiring specific adaptations of SNOMED-enabled applications.
The requirements for Extensions can be summarized as follows:
Structure and Content Guide | 23
• Support for extra terminology components including Concepts, Descriptions, Relationships and Subsets:
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