# Validating

SNOMED CT Expression Constraints can be automatically validated to ensure that they conform to a variety of rules, including:

* Expression constraints must conform to one of the syntaxes defined in [5-syntax-specification](https://docs.snomed.org/snomed-ct-specifications/snomed-ct-expression-constraint-language/design/5-syntax-specification "mention"). Syntactic validation can be performed using an expression parser, as described in [7.2-parsing](https://docs.snomed.org/snomed-ct-specifications/snomed-ct-expression-constraint-language/implementation-considerations/7.2-parsing "mention")
* Expression constraints must conform to the concept model. This validation can be performed by comparing the parsed expression constraint against the rules defined in the SNOMED CT concept model
* All concept references included in the expression constraint must be valid. In most cases this means that the concept references must refer to active concepts in the given version and edition of SNOMED CT
* All concept references used to refer to attribute names must be a descendant of [246061005 | Attribute|](http://snomed.info/id/246061005)
* All concept references to which a memberOf function is applied must be a descendant of [900000000000455006 | Reference set|](http://snomed.info/id/900000000000455006)

Please note that some of these rules may not apply in all environments.

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