Describes requirements for terminology services to load data from different release types in SNOMED CT release packages.

Organizations that maintain or must distribute one or more . Each release package must contain a for the current version of an edition or extension for which they are responsible. Optionally, each release package may also contain a and/or for the same version of the same edition or extension.
Terminology service providers must ensure their service is able to import data from either a full or snapshot release of a selected edition or extension. They should also consider enabling the service to update a previously imported edition or extension using a delta release.
Healthcare application providers should ensure that their application can work with terminology services that facilitate importing and updating SNOMED CT using the release types available for all the SNOMED CT editions and extensions to which their customers require access.
Terminology service users must confirm that the healthcare applications and terminology services they procure can provide access to the SNOMED CT editions and extensions they need to access. They must also confirm that the terminology service facilitates updates to more recent versions of those editions and extensions.

Release Type Characteristics and Uses

specifies the content of each of the and the types of use that these release types support.

SNOMED CT Release Types

Release Type	Description	Usage notes
Full		The set of full release files for a provides data that enables terminology services to offer access to of terminology content at any specified date between its first release and the current release. The data in a set of full release files for an edition also enables terminology services to provide information about changes made to the content of that edition between any two release dates.
Snapshot	The version of each component and reference set member in a snapshot release is the most recent version of that component at the time of the snapshot. Components that have been added, changed or inactivated in the current release have an effectiveTime equal to the release date. Components that have not changed since an earlier release have an effectiveTime that matches the release in which they were most recently added, changed or inactivated. Components that are inactive are included and must be distinguished from active components based on the value in the active column.	A set of snapshot release files for a provides data that enables terminology services to offer access to the current release of the content of that edition. Access to snapshot release file data for two or more releases of an edition, also enables terminology services that provide information about changes made to that edition between the release dates of those snapshots.
Delta		The content of a set of delta release files for a cannot be used as a stand alone resource but can be used in the following ways: To update the previous full release data: by adding the data in each delta release file to the current stored version of the full release. To update the previous snapshot release data: by adding new components and replacing existing components with updated versions of those components. To enable review of changes to components since the previous release: by comparing the delta data with the previous snapshot data for the same edition.

Comparing the Content of Different Release Types

provides an illustration of the content of the delta, full and snapshot release types across five releases of a simplified example release file. The names of the four columns in this example file match four of the columns in the SNOMED CT descriptions release file. However, to simplify the example, the moduleId, conceptId and caseSignificanceId columns have been omitted, and the values in the id columns are simple integers rather than . Each of the five releases in the diagram is shown with a valid effectiveTime (for presentational clarity the release dates shown are a year apart and the year is shown in bold text). provides a key to use of color shading to highlight additions, changes and inactivations in each version of the release.

Illustration of Content of Different Release Types

Release and Notes

Delta

Full

Snapshot

20010131 - The first release illustrating the initial content of the release file.

In this example, six components are created and included in the first release.

The delta, full, and snapshot release files are identical in the first release because there are no earlier versions of any components.

The delta represents the changes from an empty starting file and thus, like the full release, it contains all the component versions ever created.
Since there is only one version of each component, this is by definition the latest version of that component, so all the and as there is only one version of each identified component so the same data is also present in the snapshot file.

id	effective Time	active	term
1	20010131	1	first
2	20010131	1	second
3	20010131	1	3rd
4	20010131	1	forth
5	20010131	1	V
6	20010131	1	VI

id	effective Time	active	term
1	20010131	1	first
2	20010131	1	second
3	20010131	1	3rd
4	20010131	1	forth
5	20010131	1	V
6	20010131	1	VI

id	effective Time	active	term
1	20010131	1	first
2	20010131	1	second
3	20010131	1	3rd
4	20010131	1	forth
5	20010131	1	V
6	20010131	1	VI

20020131 - The second release illustrating a change.

Component 3 term changed from "3rd" to "third".

The delta file only includes the changed item.

The full file includes all rows in the previous release plus the changed row with the new release date and updated term.

The snapshot view includes only the most recent version of each component. So the initial version of component 3 is omitted.

id	effective Time	active	term
3	20020131	1	third

id	effective Time	active	term
1	20010131	1	first
2	20010131	1	second
3	20010131	1	3rd
3	20020131	1	third
4	20010131	1	forth
5	20010131	1	V
6	20010131	1	VI

id	effective Time	active	term
1	20010131	1	first
2	20010131	1	second
3	20020131	1	third
4	20010131	1	forth
5	20010131	1	V
6	20010131	1	VI

20030131 - The third release illustrating two additions.

Components 7 and 8 added with term "fourth" and "fifth" respectively.

The delta file only includes the added items.

The full file includes all rows in the previous release plus the added rows with the new release date.

The snapshot view includes only the most recent version of each component including the newly added components.

id	effective Time	active	term
7	20030131	1	fourth
8	20030131	1	fifth

id	effective Time	active	term
1	20010131	1	first
2	20010131	1	second
3	20010131	1	3rd
3	20020131	1	third
4	20010131	1	forth
5	20010131	1	V
6	20010131	1	VI
7	20030131	1	fourth
8	20030131	1	fifth

id	effective Time	active	term
1	20010131	1	first
2	20010131	1	second
3	20020131	1	third
4	20010131	1	forth
5	20010131	1	V
6	20010131	1	VI
7	20030131	1	fourth
8	20030131	1	fifth

20040131 - The fourth release illustrating inactivation.

Component 4 is inactivated.

The delta file only includes the inactivated item.

The full file includes all rows in the previous release and the inactivated row with the new release date.

The snapshot view includes only the most recent version of each component. So the only version component 4 included is the new inactive version.

id	effective Time	active	term
4	20040131	0	forth

id	effective Time	active	term
1	20010131	1	first
2	20010131	1	second
3	20010131	1	3rd
3	20020131	1	third
4	20010131	1	forth
4	20040131	0	forth
5	20010131	1	V
6	20010131	1	VI
7	20030131	1	fourth
8	20030131	1	fifth

id	effective Time	active	term
1	20010131	1	first
2	20010131	1	second
3	20020131	1	third
4	20040131	0	forth
5	20010131	1	V
6	20010131	1	VI
7	20030131	1	fourth
8	20030131	1	fifth

20050131 - The fifth release illustrating a typical situation with updates of different types.

Component 5 is inactivated.
Component 6 is changed with the revised term "sixth".
Component 9 is added with the term "seventh".

id	effective Time	active	term
5	20050131	0	V
6	20050131	1	sixth
9	20050131	1	seventh

id	effective Time	active	term
1	20010131	1	first
2	20010131	1	second
3	20010131	1	3rd
3	20020131	1	third
4	20010131	1	forth
4	20040131	0	forth
5	20010131	1	V
5	20050131	0	V
6	20010131	1	VI
6	20050131	1	sixth
7	20030131	1	fourth
8	20030131	1	fifth
9	20050131	1	seventh

id	effective Time	active	term
1	20010131	1	first
2	20010131	1	second
3	20020131	1	third
4	20040131	0	forth
5	20050131	0	V
6	20050131	1	sixth
7	20030131	1	fourth
8	20030131	1	fifth
9	20050131	1	seventh

Key to Color Shading in the Release Type Illustration Table

Color	Description
White	Component unchanged in this release and this is the most recent version of this component.
Grey	This is not the most recent version of this component. One or more of the releases since the effectiveTime of this row have either changed or inactivated this component. As these rows are not the most recent version of the identified component, they do not appear in the snapshot view.
Green	The first version this component as added in this release.
Yellow	An updated version of an existing component. The updated version is present in the current release and includes a change to one or more data values.
Red	An updated version of an existing component that inactivates the component.

The formal specification of these release types is in Section 3.2 Release Types of the SNOMED CT Release File Specifications.
If the does not include a or , that match the content of these release types can be derived from the .