Extensions Practical Guide

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Prior to creating an extension, each organization must obtain a unique namespace identifier from SNOMED International (see http://snomed.org/changeadd). Once the namespace identifier is issued, SNOMED International authorizes the allocated organization to generate SCTIDs within their allocated namespace to identify extension components. Each SNOMED CT namespace identifier is 7 digits in length. By including this 7 digit identifier in the appropriate position within an SCTID, and maintaining locally unique item identifiers, global uniqueness of SCTIDs can be ensured.

Info
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To apply for a namespace identifier, please fill out a namespace identifier application form and email it to info@snomed.org.

For a list of existing namespaces, please visit the SNOMED CT Namespace Identifier Registry. 

For more information, please visit Note: Information about applying for a namespace identifier can be found on the SNOMED International website at http://snomed.org/changeadd.

Examples

The table below lists some examples of namespace identifiers and the organizations to which they are allocated. These organizations include 

Gloss
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tNational Release Centers
 (or NRCs), local organizations, and commercial vendors. Note that this table is an excerpt from the SNOMED CT Namespace Registry as of October, 2017.

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CapIdexamples-of-namespace-identifiers
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Examples of namespace identifiers


Namespace IDOrganization
1000124National Library of Medicine (USA) – IHTSDO Member
1000087

Canada Health Infoway (Canada) – IHTSDO Member

1000052National Board of Health and Welfare (Sweden) – IHTSDO Member
1000119Kaiser Permanente
1000129B2i International LLC

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CapRefTypeFigure below illustrates the structure of an extension SCTID using the concept 

Concept
t5281000124103 |Persistent asthma|
 from the 20170301 US Edition of SNOMED CT. The structure of the SCTID has been labeled and the namespace identifier is shown in red. Note that the spaces do not form part of the SCTID and have been added to improve readability.

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CapIdeg-sctid
CapTypeFigure

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Info
titleCaution

The namespace identifier used in an extension's SCTIDs should NOT be used as the mechanism to determine which edition or extension a component belongs to. Instead, the moduleId attribute is used for this purpose. For more information, see 4.2 Modules.

For example, although

Concept
t6811000087108 |CT guided biopsy of left lower limb|
 includes the namespace identifier "1000087" (allocated to Canada Health Infoway) and the partition identifier "10", this concept belongs to the
Concept
ShowPartsterm
t900000000000207008 |SNOMED CT core module|
 in the International Edition. The presence of the Canadian namespace identifier in this SCTID indicates that this concept was originally created by Canada Health Infoway and later promoted into the International Edition. For further information on content promotion, please refer to 5.7.1.3 Updating Extension.

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