Compositional Grammar Specification

The SNOMED CT Compositional Grammar is a formal, lightweight syntax for representing SNOMED CT expressions — structured combinations of one or more concept identifiers that convey precise clinical meaning. Designed to be both human-readable and machine-parsable, the grammar has evolved through multiple versions since its initial specification, incorporating formal ABNF definitions, enhanced character encoding rules, and support for concrete values such as numbers, strings, and booleans. This specification defines the grammar, provides examples, and offers guidance for implementing it in systems such as EHRs, decision support tools, and terminology services, ensuring consistent and interoperable representation of clinical ideas across diverse healthcare contexts.

---

Introduction

Design

Examples

Implementation Guidance

Appendices

---

© Copyright 2025 International Health Terminology Standards Development Organisation, all rights reserved.

This document is a publication of International Health Terminology Standards Development Organisation, trading as SNOMED International. SNOMED International owns and maintains SNOMED CT®.

Any modification of this document (including without limitation the removal or modification of this notice) is prohibited without the express written permission of SNOMED International. This document may be subject to updates. Always use the latest version of this document published by SNOMED International. This can be viewed online and downloaded by following the links on the front page or cover of this document.

SNOMED®, SNOMED CT® and IHTSDO® are registered trademarks of International Health Terminology Standards Development Organisation. SNOMED CT® licensing information is available at http://snomed.org/licensing. For more information about SNOMED International and SNOMED International Membership, please refer to http://www.snomed.org or contact us at [email protected].