> For the complete documentation index, see [llms.txt](https://docs.snomed.org/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.snomed.org/snomed-ct-specifications/snomed-ct-owl-reference-set-specification/design-considerations/2.1-reference-set-type.md).

# Reference Set Type

The [I OWL expression type reference set|](http://snomed.info/id/762676003) represents components and their associations to OWL expressions, e.g. definitions specified in OWL expressions for concepts, or information about OWL ontologies of SNOMED CT. This new type of reference set follows the pattern for annotation type reference set, but the content are not mixed with other types of annotations. The new refset supports accurate representation for feeding data into Description Logic reasoners, validation of OWL expressions, and creation of OWL ontologies for SNOMED CT.

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