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With every release of SNOMED CT, two types of relationship files are distributed: the Stated Relationship file, containing the defining relationships stated by the terminology authors; and the Relationship file, containing the full set of relationships that can be inferred using a classifier (excluding non-redundant 

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relationships). It is important that extension producers are aware of the difference between these two files, and the fact that most consumers of the terminology will use the Relationship file (containing the inferred relationships). The Stated Relationship file is primarily used by extension producers, but may also be used by terminology consumers that have access to a description logic classifier.

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OWL Expression Reference Set

Include Page
DOCRELFMT:OWL Expression Reference Set file DOCRELFMT:OWL Expression Reference Set file DOCTSG:9.1 Stated Relationships File DOCTSG:9.1 Stated Relationships File

Inferred Relationships

Inferred relationships are derived from the set of stated defining relationshipsof 

Gloss
t OWL axioms

 in the OWL Expression Reference Set, by applying a consistent set of logical rules to the definition which take account of the definitions of related concepts.

Several semantically equivalent views may be inferred from the same set of stated relationships. However, the SNOMED CT Relationship file is distributed using an inferred view known as the Distribution Normal Form (DNF)

Gloss
t necessary normal form (NNF) GlosTerm necessary normal form

. This standard distribution view, includes all non-redundant 

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 relationships (between each concept and its proximal supertype), and the inferred concept definition of each concept (including all non-redundant defining relationships). For more information, please refer to the  Inferred definition views section in the Terminology Services Guide. Please note that in the standard distribution

In the necessary normal view (DNF):

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NNF) appropriate subtype and attribute relationships are created to represent non-redundant axioms that are necessarily true capable of being represented using the relationship file format.

Note
Some more advanced axioms (e.g.  Gloss t general class inclusions )  can be represented in the OWL Expression Reference Set but cannot be represented in the Relationship File.

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Example

This example is included to illustrate what happens during the classification process.

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