Extensions Practical Guide

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The diagram below illustrates how extension content is promoted to the SNOMED CT International Edition.


Caption label
CapIdpromoting-content-to-the-international-edition
CapTypeFigure
Promoting content to the International Edition

Content Demotion

In some circumstances it may be necessary to demote SNOMED CT components. Demotion means moving a component from a given module to a module that is dependent on it. For example, moving a concept (and its associated descriptions and stated relationships) from the International Edition to a National Extension.

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If content demotion is deemed necessary, then it is very important to use a safe approach. As shown in the diagram below, the recommended approach for demoting SNOMED CT content is to inactivate the component in the source module and activate the component in the destination module at a more recent effective time.

Caption label
CapIddemoting-content-from-the-international-edition-to-extension
CapTypeFigure
Demoting content from the International Edition to extension

Updates should also be made to the respective component inactivation reference sets to indicate that the component has been inactivated because 

Concept
ShowPartsterm
t900000000000487009 |Component moved elsewhere|
, and to the 
Concept
ShowPartsterm
t900000000000524003 |MOVED TO association reference set|
 to indicate the module to which the component has been moved. For more information on inactivation and historical associated reference sets, see  3.2.6.3. Managing Component Inactivation. 

The following diagram shows the RF2 file changes that are required to demote an example concept from the international edition to an extension module. Please note that it is essential that the effectiveTime of the active component in the destination module is more recent than the effectiveTime of the inactive component in the source module. This is done to ensure that the demoted component is seen as active in any edition that uses the extension module to which it was demoted.

Caption label
CapIdfile-changes-required-to-demote-a-concept
CapTypeFigure
File changes required to demote a concept


Warning

Some approaches to content demotion that have previously been proposed are considered to be unsafe. The content demotion approaches that should never be used include:

  • Removing every instance of the component from the International Edition (or source edition)
    • This approach will delete the history of the component for users of the International Edition, who do not use the demoted content. The history of each SNOMED CT component should be traceable in the edition in which the component was created.
  • Retaining the component active in the source module, and creating a new version of the component (i.e., with a more recent effectiveTime) in the less dependent module
    • This approach will make the component visible and accessible in the source edition, and users of the source edition would not be aware that the component was demoted to a less dependent module
    • This approach may lead to inconsistency between the version of the component in the International Edition and the version in the less dependent module. 

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