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SNOMED CT
Release Format 2 is designed to enable the distribution and use of a full historical view of
SNOMED CT from its first release in 2002 up to its most recent release. This allows
terminology servers to provide a range of different views of
SNOMED CT . However, it does not require that all
terminology servers support the full range of views.
identifies three options for the views that a
SNOMED CT terminology server may support. The simplest of these is the single
snapshot view which provides access to a single
release version . This closely matches the view provided by the original
SNOMED CT release format (
RF1 ). The most powerful
full view which allows the server to provide access to any selected version of
SNOMED CT from a single representation of the
SNOMED CT resource. This makes full use of the version features in
RF2 . Alternatively a server may provide a selected set of snapshots representing versions
of known interest to its users.
People designing a
terminology server need to decide whether their server will only provide access to a single current
view of the
SNOMED CT resource or will also support retrospective views of earlier versions of the terminology.
The single
snapshot view is simplest to implement and matches the service most vendors offered with original
SNOMED CT release format (
RF1 ). A more complete view is now possible using
Release format 2 and this offers several significant advantages. It supports incremental updates allowing
smoother transition as new versions become available. It also allows changes between
versions to be detected more easily and can be used to evaluate queries against an
earlier version for comparative purposes.
People choosing a
terminology server need to consider whether a server that only supports a single
snapshot view of the current version meets their requirements. If they require access to previous
versions a server that supports the
full view is likely to be the best long term solution. A server that allows access to multiple
discrete snapshots may provide a reasonable interim solution but may be less flexible
and less easy to maintain.
Table 1. SNOMED CT views that may be supported by terminology servers |
|
---|---|
View |
|
A snapshot view terminology service provides access to the content of the current state of all the components of the International Release and any chosen Extension Releases . |
|
Multi- snapshot view |
A "multi- snapshot view " terminology service provides access to:
|
A Full view terminology service provides access to:
|
The
full view is required to support some
SNOMED CT use cases but many requirements can be adequately met by providing access to a current
Snapshot view . The multi-
snapshot view is an approach that may meet some requirements that are not met by a single snapshot
without requiring support for the
Full view .
Note:
terminology servers that do not support the
Full view still need to be able to import from a
Full release as
Extension providers are not required to provide the snapshot or
delta releases (
Importing release types )