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

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104 | <strong>SNOMED</strong> CT <strong>Release</strong> <strong>Format</strong> 1 (<strong>RF1</strong>) <strong>Guide</strong> July 2012<br />

3.2.1. <strong>Release</strong> <strong>Format</strong> 1 - Overview<br />

The tables and related mechanisms used to represent <strong>SNOMED</strong> CT Components and Derivatives in <strong>Release</strong><br />

<strong>Format</strong> 1 are summarized below.<br />

Figure 34: <strong>SNOMED</strong> CT Data Structure Overview<br />

• Core Tables: The Core Tables contain the Concepts, Descriptions, and Relationships of the <strong>SNOMED</strong><br />

CT terminology.The other structural mechanisms support and enrich the core table structure for terminology<br />

implementers. Briefly, these other mechanisms include.<br />

• History: History files are typically useful for upgrading an implementation of <strong>SNOMED</strong> CT to a new<br />

<strong>SNOMED</strong> CT release. History files include a log of Concept and Description additions, inactivations and<br />

minor changes. History files also include information about what concepts can be used in place of inactivated<br />

(retired) concepts.<br />

• Subsets: Subsets define a smaller collection of <strong>SNOMED</strong> CT Concepts, Descriptions, or Relationships.<br />

• Cross Mappings: Cross Mappings relate <strong>SNOMED</strong> CT to a target classification or coding scheme such<br />

as ICD-9 or ICD-10, in order to allow <strong>SNOMED</strong> CT -encoded data to be expressed using the target scheme<br />

for a particular purpose or use case.<br />

• Extensions: Extensions consist of terminology content developed to supplement, but not replace, the<br />

content contained in the International <strong>Release</strong>. Extension content may be used to meet requirements that<br />

are not sufficiently universal to justify the creation of International <strong>Release</strong> content. An example would be<br />

a national drug extension, containing concepts for the proprietary drugs available within a particular country.<br />

Extensions may be developed and maintained by the IHTSDO, a National <strong>Release</strong> Center or an authorized<br />

.<br />

• Developer Toolkit : Tables in the Developer Toolkit can be helpful for software developers directly or as<br />

examples that can be customized by installation and include:<br />

• Indexes, Word Equivalents, and Duplicate Term files that are helpful for search applications;<br />

• Sample Navigational Hierarchies that can be used to manage the display of <strong>SNOMED</strong> CT concepts<br />

and viewing sequences.<br />

• Canonical Table: The canonical table is useful for determining the logical equivalence of concepts that<br />

may be represented in multiple ways.<br />

This guide provides details about the <strong>SNOMED</strong> CT data structures. This section provides an overview of the<br />

structure and answers some of the frequently-asked questions which may be helpful if you are new to <strong>SNOMED</strong><br />

CT.<br />

© 2002-2012 International Health Terminology Standards Development Organisation CVR #: 30363434

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