# constraintProperty

Indicates a property used as a constraint. For example, in the definition of a [StatisticalVariable](https://schema.org.ai/StatisticalVariable). The value is a property, either from within Schema.org or from other compatible (e.g. RDF) systems such as DataCommons.org or Wikidata.org.

## Expected Types

| Type | Description |
|------|-------------|
| [Property](https://schema.org.ai/Property) | A property, used to indicate attributes and relationships of some Thing; equivalent to rdf:Property. |
| [URL](https://schema.org.ai/URL) | Data type: URL. |

## Used on Types

| Type | Description |
|------|-------------|
| [ConstraintNode](https://schema.org.ai/ConstraintNode) | The ConstraintNode type is provided to support usecases in which a node in a structured data graph is described with properties which appear to describe a single entity, but are being used in a situation where they serve a more abstract purpose. A [ConstraintNode](https://schema.org.ai/ConstraintNode) can be described using [constraintProperty](https://schema.org.ai/constraintProperty) and [numConstraints](https://schema.org.ai/numConstraints). These constraint properties can serve a variety of purposes, and their values may sometimes be understood to indicate sets of possible values rather than single, exact and specific values. |

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Quoted from Schema.org 30.1, https://schema.org/constraintProperty, under CC BY-SA 3.0. Served by the Org.AI Foundation at https://schema.org.ai/constraintProperty.