> 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/introduction/1-introduction.md).

# Introduction

## Background

SNOMED CT is a clinical terminology with a comprehensive coverage of wide clinical specialties and requirements. The development and maintenance of SNOMED CT relies on Description Logics (DL) and its reasoning services. The stated relationship file has been used to represent DL definitions. However, it is unable to fully represent semantics of the DL expressivity due to the limitation of its relational structure.

The new OWL refsets are designed to replace the stated relationship file and it represents the DL definitions for SNOMED CT content by following the international standard of OWL 2 Web Ontology Language.

## Purpose

The purpose of this document is to define and describe the OWL Reference Set.

## Scope

The document presents the specification of OWL refsets. It also documents the background, design considerations, quality assurance, and distribution format of the OWL refsets.

The implementation of the OWL refsets in the applications, and transformation of it to an OWL ontology, are out of the scope.

## Audience

The target audiences of this document include:

* SNOMED CT national release centers;
* SNOMED CT terminology content developers and technical developers;
* SNOMED CT implementers, analysts, and developers of electronic health records and information systems.

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