New guide in development
The identifiers assigned to all components that originated as part of an extension include a namespace-identifier (see Representing SNOMED CT Identifiers). This means that the sets of Identifiers available to each organization authorized to issue components are distinct, which ensures that the same Identifier cannot be issued by two different organizations .
Figure 31. SCTID for a concept originated as part of an Extension
All Extension components (rows) originated by an organization must use the Namespace Identifier assigned to that organization. Namespace Identifiers are issued by the SNOMED International so that the Namespaces remain unique between organizations. Allocated Namespaces are recorded as Concepts in the 900000000000441003 |SNOMED CT Model Component| hierarchy ("special concepts " hierarchy in RF1) when they are issued to an organization .
- Preventing collision or reuse of SNOMED CT identifiers ;
- Indicating the origin of a component. In RF2 responsibility for maintenance is tracked only by the ModuleId, this is the field that should be used to avoid potential risk of two organizations make conflicting changes to the same component .
- Indicating the source for information about a concept - relevant for Extension Concepts that are not directly available in a particular system.
All Extension components (rows) should use the appropriate partition-identifiers for Extensions. This ensures that components of the SNOMED CT International Release can be distinguished from components that are part of an Extension .
Note: Components that originate as part of the International Release do not have a namespace field and are distinguished instead by partition-identifier values that are specific to International Release .
Note: Each organization can assign the item- Identifier portion of the SCTID in any way within its Namespace. If there is a need to allocate part of the development process to a subdivision within an organization, they may be allocated a set or range of item-identifiers that have not yet be used or allocated within that Namespace. The authorized organization must ensure that it tracks and manages all such allocations in a way that avoids any risk of reuse of the same SCTID .