# attribute cardinality constraint

## attribute cardinality constraint

A constraint on the number of times that a specific attribute may be included in the same concept definition or expression.

#### Notes

* Constraints on *attribute cardinality* apply only to non-redundant attributes. A redundant attribute is an attribute with a value that is subsumed by another attribute in the same *concept* definition or *expression*.
* Cardinality constraints are represented by square brackets containing a minimum value value represented as an integer, optionally followed by two dots and a maximum value represented as an integer or as an asterisk \*\*\*\*\*.
  * If the maximum is omitted then the maximum cardinality is the same as the minimum cardinality.
  * If the maximum is an asterisk \*\*\*\*\* the maximum cardinality is unlimited.

#### Examples

* The following expression constraint is satisfied by any clinical finding whose definition has two or more non-redundant finding sites, irrespective of the attribute group in which they are contained.

< [404684003 |Clinical finding|](http://snomed.info/id/404684003) : \[2..\*] [363698007 |Finding site|](http://snomed.info/id/363698007) = < [91723000 |Anatomical structure|](http://snomed.info/id/91723000)

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