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

2.3.3.2. Specification for Namespace within the SCTID
The identifiers assigned to all components that originated as part of an extension include a namespace-identifier
(see Representing SNOMED CT Identifiers (2.3.2)). 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 32: 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 IHTSDO so that the Namespaces remain
unique between organizations . Allocated Namespaces are recorded as Concepts in the | SNOMED CT
Model Component |hierarchy ("special concepts" hierarchy in RF1) when they are issued to an organization
.
Namespaces serve three Roles:
• Preventing collision or reuse of SNOMED CT identifiers;
• Indicating the origin of a component and tracking responsibility for maintenance - avoiding 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.
2.3.3.3. Namespace allocation
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Namespace-identifiers are allocated by the IHTSDO to licensed organizations . The IHTSDO is under no
obligation to allocate a namespace to any organization and makes these allocations at its discretion.
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