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The standard format for distributing SNOMED CT reference sets are the reference set format, as described in  4.2. Common Reference Set Format.  E.g.  For example, an extensional definition of a subsets of components is represented as a simple reference set, and the standards standard format for distributing intensional definitions of concept subsets is as a  query specification reference set. As part of the SNOMED CT release format, reference sets support unique identification, versioning and recognition of dependencies. 

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Other distribution formats may be used where necessary. For example to comply with requirements for representation of value sets including codes from other code systems. . HoweverHowever, care should be taken to ensure that distributed subsets are uniquely identified and versioned. Subsets need to be accessed, selected and where appropriate bound to information models using standard approaches.

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Some subsets will be distributed biannually as part of the International Release; however. However, some others may not require this release schedule. Release processes must include a period of time dedicated to subset manipulation, following the 'freezing' of  SNOMED CT itself. This is the period where all the changes has been made to the core components of SNOMED CT database itself. Timing of release and distribution of specific subsets will be dictated by individual use case-specific requirements. These should be identified and documented initially as part of the subset development process. These may change over time based on user feedback.