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Expression Constraint Language - Version 1.2 Available

February 19, 2017

Please note that version 1.5 of the SNOMED CT Expression Constraint Language Specification and Guide is available at:

SNOMED International is pleased to announce the publication of version 1.2 of the Expression Constraint Language at

The Expression Constraint Language is a formal syntax for representing computable rules used to define sets of clinical meanings. Expression constraints can be used to define intensional reference sets, to query SNOMED CT data, and to restrict the valid values in an information model.

ECL version 1.2 incorporates updates that were requested by implementers of the language, including:

  • The ability for the memberOf function to be applied to a set of reference set concepts defined using an expression constraint; and

  • A correction to the definition of numericValue to allow negative decimal values to be fully supported.

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