Release Types and Versioned Views
Importing Release Types
Requirements
Organizations that maintain SNOMED CT edition(s) or extension(s) must distribute one or more release package(s).
Each release package must contain a full release for the current version of an edition or extension for which they are responsible.
Optionally, each release package may also contain a snapshot release and/or delta release for the same version of the same edition or extension.
Terminology service providers must ensure their service can import data from either a full or snapshot release of a selected edition or extension.
They should also consider enabling their service to update a previously imported edition or extension using a delta release.
Healthcare application providers should ensure that their applications can work with terminology services that support importing and updating SNOMED CT using the available release types.
Terminology service users must confirm that the healthcare applications and terminology services they procure:
Provide access to the SNOMED CT editions and extensions they require.
Support updates to more recent versions of those editions and extensions.
Release Type Characteristics and Uses
Full
Release files contain every version of every component and reference set member ever released. Enables access to any snapshot view and comparisons between releases.
Snapshot
Release files contain only the most recent version of every component and reference set member as at the release date. Enables access to the current release snapshot and comparison of changes between snapshots.
Delta
Release files contain only rows representing versions created since the previous release date. Supports incremental updates to full or snapshot data and reviewing changes between releases.
Note: Delta files have been removed from the SNOMED International release package, Managed Service Extensions and Derivative packages. Instead, a Delta Generation Tool is available to create deltas between two fixed release dates.
If the release package does not include a snapshot release or delta release, equivalent views can be derived from the full release.
Comparing the Content of Different Release Types
The following sections illustrate the differences between delta, full, and snapshot release types across five releases of a simplified example release file.
Key to Symbols
⚪
Unchanged component (still active and unchanged in this release)
🟩
New component added in this release
🟨
Updated version of an existing component
🟥
Inactivated version of a component
◼️
Not the most recent version (historical row)
Release 20010131 — First release
Six components created.
Delta, Full, and Snapshot are identical (no previous release).
Delta, Full, Snapshot:
🟩 1
20010131
1
first
🟩 2
20010131
1
second
🟩 3
20010131
1
3rd
🟩 4
20010131
1
forth
🟩 5
20010131
1
V
🟩 6
20010131
1
VI
Release 20020131 — Second release
Component 3 changed from
3rd→third.
🟨 3
20020131
1
third
Release 20030131 — Third release
Components 7 (
fourth) and 8 (fifth) added.
🟩 7
20030131
1
fourth
🟩 8
20030131
1
fifth
Release 20040131 — Fourth release
Component 4 inactivated.
🟥 4
20040131
0
forth
Release 20050131 — Fifth release
Component 5 inactivated.
Component 6 changed to
sixth.Component 9 added (
seventh).
🟥 5
20050131
0
V
🟨 6
20050131
1
sixth
🟩 9
20050131
1
seventh
Supporting Versioned Views
Requirements
All SNOMED CT release packages must include a set of full release files for a SNOMED CT edition or extension.
A full release includes the complete history of the content of that edition or extension.
This allows a terminology server to enable access to versioned views of the content of this edition or extension as it was at any point between its first release and the current release.
The extent to which a terminology service supports access to different versioned views may vary.
Terminology service providers must:
Optimize performance of access to the current snapshot view of a selected edition or extension.
Provide access to earlier snapshot views and delta views to support:
Analysis of data entered using earlier versions.
Terminology change management when updating to newer versions.
Healthcare application providers must ensure that their applications can use terminology services that provide access to required versioned views of SNOMED CT.
Services that support access to the current snapshot view should be selected and optimized.
Services that enable access to a new version of the same edition should also be accessible to manage updates.
Access to earlier versions should be available to support analysis of data recorded with content that has since been inactivated.
Terminology service users must procure applications and services that:
Optimize access to the current snapshot view of the selected versioned edition.
Support updates to newer versions.
Support analysis of data recorded using content that has since been inactivated.
Types of Versioned Views
A versioned view is a set of component versions and reference set member versions defined by the characteristics of their effectiveTime.
Versioned views and release types are closely related.
A release type is a physical representation of a particular versioned view.
Some versioned views are not instantiated as release types, but all valid views of a SNOMED CT edition can be generated from a full release.
Snapshot view
Includes the most recent version of all components and reference set members at a specified point in time.
Uses:
The current snapshot view is the most important and is in constant use during daily operations.
When updating to a new version, access to the earlier snapshot is required to determine the type of change made to each component.
When reviewing, analyzing, or reporting older data, snapshot views from the relevant time may help interpret unexpected variations.
Delta view
Includes only rows representing changes to components and reference set members since a specified date or between two dates.
Uses:
When updating to a new version, delta views identify components that were added, updated, or inactivated between releases.
Full view
Includes all versions of all components and reference set members in a full release.
Uses:
Useful for organizations that do not apply every update, but still need to interpret data that references content not in the snapshot view they use.
Access to earlier full views may be required for forensic review or anomaly resolution.
Terminology Service Versioned View Options
Single snapshot view of an edition
Supports only one preset snapshot view (the current version). ✅ Meets requirements for current data entry and display. ❌ Does not meet requirements for change management, retrospective data analysis, or access to modules outside the edition.
Multiple snapshot views of an edition
Supports views for a limited set of versions (e.g., current and previous). Versions can be specified in requests. ✅ Meets requirements for data entry, display, and change management. ⚠️ Partially meets requirements for retrospective data analysis. ❌ Does not meet requirements for access to modules outside the edition.
All snapshot views of an edition
Supports snapshot views for any point in time within an edition. ✅ Meets requirements for data entry, display, change management, and retrospective data analysis. ❌ Does not meet requirements for modules outside the edition.
All snapshot views of a range of different editions
Supports snapshot views for multiple editions. ✅ Meets requirements for data entry, display, change management, retrospective data analysis, and access to modules from any supported edition.
Delta views that may be supported
Single delta view (current vs. previous version)
Shows changes between the current version and the previous version of an edition. Useful for reviewing the most recent changes. Also requires access to the snapshot of the previous release.
Multiple delta views (between adjacent versions)
Shows changes between earlier releases (each version vs. its predecessor). Useful for reviewing historical changes and addressing issues retrospectively. Requires access to the snapshot view prior to each delta.
Configurable delta views (between any two dates)
Flexible solution showing changes between any two specified points. Requires access to a full release. Supports identifying all changes within the period. May include one or all changes for each component.
Configurable delta views across multiple editions
Shows changes between two points across one or more editions. Useful in cases where multiple editions are in use.
Creating and Updating Versioned Views
Full views
To enable terminology services to access a full view of a SNOMED CT edition:
Import a full release of the edition into an appropriate datastore.
To update:
Import the latest full release, replacing the old data; or
Import the latest delta release and append it to the existing full release data.
Snapshot views
To provide access to a snapshot view:
Import the current snapshot release; or
Selectively import data from the current full release (most recent versions only); or
Filter the full view to include only the most recent version of each component before a specified date.
To update to a new snapshot view:
Use any of the above methods to add or replace a snapshot view; or
Import the latest delta release and update the snapshot accordingly.
Delta views
To provide access to a delta view:
Import the delta release for that edition; or
Selectively import rows from the full release where
effectiveTimeis after the previous release date and on or before the current release date; orFilter a full release to generate configurable delta views between arbitrary dates.
Configurable delta views may include:
Only the most recent change to each component within the period, or
All changes to each component during that period.
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