After identifying the components that have changed since the previous release, it is important to assess how these changes may affect the content of the extension. In particular, extension producers will need to ensure that the quality of the extension has not been compromised. For example, this may include checking that no relationship in the extension refers to an International Edition concept that has been inactivated, and checking for new concepts that may need to be added to reference sets in the extension.
The following table presents some examples of how changes in the International Edition may affect new versions of an extension. Please note that this list is not exhaustive, but instead provides examples of the types of maintenance tasks which are likely to be required when managing changes in an extension. Also note that extension consumers will need to assess the impact of changes in an extension edition on their implementations.
Table: Examples of terminology changes that may affect an extension
Concept inactivations
Extension Impact
A concept, which is referenced by a reference set member (i.e. the referencedComponentId) in the extension, has been inactivated.
Reference sets are permitted to reference inactive components as there are valid use cases for this. However, it is recommended that inactive components are not for capturing clinical data. Therefore, if the extension reference set may be used by consumers for clinical data capture, the associated reference set member should be inactivated, and a potential replacement considered. For more information please refer to . Potential replacements for the inactivated concept can be found in the relevant
A concept, which is the parent of an extension concept (i.e. it is the destinationId of a relationship of type ), has been inactivated.
To retain the referential integrity of the extension, it is important that all extension concepts are subsumed (via active concepts) by the root concept in the International Edition. When the parent of an extension concept is inactivated, the associated relationship in the extension must also be inactivated, and a new relationship created to link the concept to an alternative international parent concept. For more information please refer to and .
A concept, which is used in an extension relationship (i.e. in the sourceId , typeId or destinationId of the relationship), has been inactivated.
When a concept is inactivated, all relationships in which that concept participates in (as the sourceId, typeId or destinationId) must also be inactivated. For more information please refer to .
When an extension concept references a concept from the International Edition which has been inactivated, the extension concept should be updated to apply active concepts. This may involve updating the modeling of a concept to use the suggested active replacements as they are stated in the relevant .
Concept additions
Extension Impact
A concept has been added to the International Edition, on request by the extension producer, and a corresponding concept has been temporarily added to the extension in the interim.
If a new concept is added to the International Edition, which represents the same meaning as a concept in the extension, the extension concept should be inactivated. Any references to the inactivated extension concept should be replaced by references to the new international concept. For more information, please refer to , Authoring Relationships and Authoring Reference Sets.In general, checks should to performed ensure that no fully defined concept in the extension has the same logical definition as a concept in the International Edition (or any module on which the extension depends).
A concept has been added to the International Edition, on request by the extension producer, for use in a national reference set.
A new member of the extension reference set should be added to refer to the new international concept. For more information, please refer to in .
A description, which is referenced by a reference set member (i.e. the referencedComponentId) in the extension, has been inactivated. For example, the description may be used in a national language reference set.
The reference set member that references the inactive description should be inactivated. For more information, please refer to .In some situations, the inactivated reference set member may need to be replaced by a new member. For example, if the inactivated description was being used as a preferred term in a language reference set, then an alternative preferred term should be defined for the associated concept.
Description additions
Extension Impact
A new description has been added to the International Edition, and the extension specifies the acceptability of all international descriptions.
The concept identifying a reference set, which is used in the extension, is inactivated.
If the reference set is not used in the extension, then no action is required.
If the reference set is used in the extension, a decision should be made as to whether or not the reference set is still required. If the reference set is required, then a new local version of the reference set may need to be created. For more information, please refer to .
A member of a reference set, which is used in the extension, is inactivated..
If the extension uses extension reference set members to adapt an international reference set, a decision should be made as to whether or not the inactivated member is required in the extension. If it is, then the inactivated reference set member may need to be reactivated in the extension. If not, then no action is required. For more information, please refer to .
Reference set additions
A new member of the relevant language reference set, which specifies the acceptability of the new description, may need to be created. For more information, please refer to .
Extension Impact
A new reference set is added to the International Edition.
A decision should be made as to whether or not the new reference set could replace any national or locally created reference sets. If so, then this could alleviate the associated maintenance responsibilites. For more information, please refer to .
One or more members have been added to a reference set in the International Edition.
If the extension uses extension reference members to adapt an international reference set, a decision should be made as to whether or not the new reference set members should be adopted in the extension reference set. For more information, please refer to ..
Updating an extension involves creating new versions of components and reference set members that are required in the extension. Please refer to Authoring for more information about principles and process for adding, modifying and inactivating content in an extension. In some situations, content may also need to be promoted from the extension into the International Edition (or another extension on which it depends).
When a new version of an extension is created, new rows must be added to the module dependency reference set to reflect the dependencies of the new version of the extension. The effectiveTime and the sourceEffectiveTime of the added rows must be set to the date of the new extension release. The targetEffectiveTime must be set to the version of the module on which the extension modules depends (as identified by the referencedComponentId).
Updates to the module dependency reference set are required:
For all existing rows in the module dependency reference set, to indicate that the dependency now applies to the new version of each module - ie the sourceEffectiveTime must be updated to the date of the extension release. If the extension module is now dependent on a new version of the target module, then the targetEffectiveTime must also be updated.
For any module dependency that is no longer applicable. In this case, the relevant member of the module dependency reference set should be inactivated.
For any new module dependency that applies to the new version of the extension. In this case, a new reference set member must be added to the module dependency reference set.
Given the robust versioning mechanism of SNOMED CT and the machine processable distribution format, changes made in a new version of a SNOMED CT edition are easy to identify automatically. Extension producers should ensure that they have appropriate mechanisms in place to identify changes in any edition on which their extension is dependent. To identify changes in an edition, the following release artifacts can be used:
The delta files generated from the new release
The snapshot files from the previous release
Please note : Delta files have been removed from the SNOMED International release package, but a Delta Generation Tool is available for those who need it. The Delta Generation Tool allows users to create their own Delta between two fixed release dates - you can find it here: https://github.com/IHTSDO/delta-generator-tool/releases.
These two release artifacts enable changes to be identified, and the nature of those changes understood. The delta release files provide information about all components or reference set members which have changed since the previous release. By comparing this information to the corresponding components or reference set members in the snapshot files from the previous release, stakeholders can understand which of these changes represent additions of new components or reference set members, and which represent new versions of existing components or reference set members. For more information on the different release types please refer to the .
The table below shows how the values for the active attribute in the previous snapshot and current delta can be compared to help to determine the types of change in the release.
The types of changes that components and reference set members can undergo are inactivate, reactivate, change or add. For example, if a row (with a given id) was not present in the snapshot from the previous release, and then was present (with the same id) in the current delta release with an active value of 1, then this means that a new component or reference set member has been added. If a row (with a given id) had a value of 1 in the previous snapshot, and now has a value of 1 in the current delta, then this means that the component or reference set member has been changed.
Row in the
DELTA view of
the CURRENT release
active = 0
active = 1
row not present
Row in the SNAPSHOT view of the PREVIOUS release
active = 0
-
Component / member REACTIVATED
NO CHANGE
active = 1
Component / member INACTIVATED
Component / member CHANGED
NO CHANGE
row not present
-
Component / member ADDED
-
Each new release of the SNOMED CT International Edition introduces some changes to the content in SNOMED CT. Many of these changes are additions to the breadth and depth of clinical coverage. Other changes may include new descriptions, corrections to concept definitions, and enhancements to the expressivity of the concept model. These changes are an essential characteristic of an evolving clinical terminology which seeks to support current requirements. However, each change made to the International Edition may have an impact on the content in an extension. It is therefore important to evaluate and manage these changes when reconciling an extension with a new version of the SNOMED CT International Edition (or another extension on which it depends).
The change management process can be divided into three distinct phases:
Identify changes
Assess change impact
Update extension
After change management has been performed, it is important that thorough of the resulting extension is performed.
In the following sections we discuss the three phases of change management.