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Expression Constraint Language - Specification & Guide now available

September 21, 2015

IHTSDO is pleased to announce the publication of the "SNOMED CT Expression Constraint Language Specification and Guide".

A SNOMED CT Expression Constraint is a computable rule that defines a bounded set of clinical meanings. The associated Expression Constraint Language enables intensional definitions to be created for use cases such as terminology binding, intensional reference set definitions, SNOMED CT content queries, and SNOMED CT concept model specifications.

The "SNOMED CT Expression Constraint Language Specification and Guide" defines and describes a formal language for representing SNOMED CT Expression Constraints. It includes a logical model of the language, two syntaxes, a set of example expression constraints and a summary of implementation considerations. This document is now available from the SNOMED CT Document Library. Alternatively, you can access it directly via the following link:

Additional supporting materials can be found on the IHTSDO's 'SNOMED CT Languages' Github repository:


Example ABNF parsers for each of the SNOMED CT Computable Languages can be found at

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