As part of the assessment process to determine where the requested content belongs, following points are important to take into consideration:
- The scope of various SNOMED CT Editions
Whether the request is permitted given the predefined principles around:
Editorial rules and;
Retaining the referential integrity of SNOMED CT
Scope
When a SNOMED CT Member, or Affiliate organization which maintains an extension, identifies a requirement for new content they should evaluate the request by considering the following questions:
- Does the requested content fall within the defined scope of the International Edition?
- Is the requested content likely to be required by, or of value to, more than one Member territory?
If the answer to both these questions is "yes", the organization should submit a request to SNOMED International for the inclusion of the new content. When a request originates in an Affiliate organization, it should be submitted to a National Release Center who will then forward the request to SNOMED International. In general, this content should not be added to a National or local extension, as content that falls within the defined scope of the International Edition and is required by two or more Member territories. However, in cases where there is an urgent requirement, an extension producer may add the content to their own extension as an interim solution. Please refer to Interim Content Additions below.
Similarly, if the answer to one or both of these questions is "no", the content may be suitable for inclusion in a National Edition. In this case, the following questions should be considered:
- Does the requested content fall within the defined scope of a National Edition?
- Is the requested content likely to be required by, or of value to, more than one organization within the Member territory?
If the answer to both these questions is "yes", then the organization should submit a request to the National Release Center for the addition of the required content into the National Edition. If the answer to one or both of these questions is "no", it should be considered for inclusion in a local extension. In a situation where the request is considered to be out of the scope of SNOMED CT, it may be rejected. Table 5.3.1-1 provides additional detail on the various outcomes in these considerations.
Table 5.3.1-1: Considerations relating to appropriateness of content at various levels
| Relevance of requested content | Description |
| Within the scope of the International Edition | If the content requested is within the scope of the International Edition, the organization should request that the content should be added to the International Edition. As SNOMED CT is a global clinical terminology, the scope of the International edition of SNOMED CT is constrained by a set of principles. For inclusion in the International edition, concepts must be
If there is an urgent need for additional content, it may be added to an extension as an interim measure, pending addition to the International Edition. For more information, please refer to Interim content additions below. |
| Within the scope of another extension, (National, third-party, or local extension) but outside the scope of the International Edition. | The scope of a national edition may permit the addition of content which falls outside the scope of the International Edition but is required within a country, region or territory. If the content requested is within the scope of a national edition, a request should be submitted to the relevant National Release Center. An organization may also use an extension which was produced by another organization, such as a vendor, regional body or specialist group. In this case, requests for content which fall within the scope of these extensions should be submitted to the relevant extension producer. When there is an urgent need for additional content, it may be added to an extension as an interim measure, pending addition to a national edition or externally maintained extension. For more information, please refer to Interim content additions below. |
| Outside the scope of other extensions, but relevant to the organization requesting the content. | An organization which maintains an extension is responsible for defining the scope of that extension. The scope of an extension should not overlap with the scope of the International Edition or any other extension with modules on which the extension modules depend on. Note that urgent content additions may be permitted as an interim measure, even when the content is within the scope of another edition or extension. For more information. please refer to Interim content additions below. Requested content which falls within the defined scope of an extension may be added by the organization which maintains the extension. For additional information about adding local content to an extension, please refer to 5.4 Authoring. |
| Outside the scope of SNOMED CT | The request is rejected |
Referential Integrity and Editorial Principles
When determining whether or not a request for additions or changes should be accepted for inclusion in any SNOMED CT edition, it is important to ensure that the addition or modification does not break the referential integrity of SNOMED CT. It is also important to assess whether the definition of new concepts has undesirable effects on the existing content. Finally, it should be ensured that every addition of or modification to SNOMED CT concepts conform to the rules specified by the concept model. Section 5.4 Authoring describes key principles which ensure that referential integrity is retained and that components and derivatives are created or modified in an extension in accordance with the editorial principles.
SNOMED International does not recommend that extension producers make changes which result in modifications to the International release as this can cause interoperability issues. Substantive errors, or improvements to content in the International release which are mitigated by the content in an extension, should, therefore, be forwarded to SNOMED International in a timely fashion to improve the quality of the International release.
In circumstances where the International release has been impacted by modifications in a national or local extension, a disclaimer notifying users of the differences between the extension release and the International release must accompany the national extension distribution files.
Final disclaimer goes here: (proposal found here: Re: SNOMED International response to "Discussion paper - Allowance of Extensions to Modify Core Content" ver. 2.0)
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