# ConstraintNode > [Thing](https://schema.org.ai/Thing) > [Intangible](https://schema.org.ai/Intangible) > [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. **Extends:** [Intangible](https://schema.org.ai/Intangible) ## Properties | Property | Expected Type | Description | |----------|---------------|-------------| | [constraintProperty](https://schema.org.ai/constraintProperty) | [Property](https://schema.org.ai/Property), [URL](https://schema.org.ai/URL) | 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. | | [numConstraints](https://schema.org.ai/numConstraints) | [Integer](https://schema.org.ai/Integer) | Indicates the number of constraints property values defined for a particular [ConstraintNode](https://schema.org.ai/ConstraintNode) such as [StatisticalVariable](https://schema.org.ai/StatisticalVariable). This helps applications understand if they have access to a sufficiently complete description of a [StatisticalVariable](https://schema.org.ai/StatisticalVariable) or other construct that is defined using properties on template-style nodes. | ## [Thing](https://schema.org.ai/Thing) Properties | Property | Expected Type | Description | |----------|---------------|-------------| | [additionalType](https://schema.org.ai/additionalType) | [Text](https://schema.org.ai/Text), [URL](https://schema.org.ai/URL) | An additional type for the item, typically used for adding more specific types from external vocabularies in microdata syntax. This is a relationship between something and a class that the thing is in. Typically the value is a URI-identified RDF class, and in this case corresponds to the use of rdf:type in RDF. Text values can be used sparingly, for cases where useful information can be added without their being an appropriate schema to reference. In the case of text values, the class label should follow the schema.org [style guide](https://schema.org/docs/styleguide.html). | | [alternateName](https://schema.org.ai/alternateName) | [Text](https://schema.org.ai/Text) | An alias for the item. | | [description](https://schema.org.ai/description) | [Text](https://schema.org.ai/Text), [TextObject](https://schema.org.ai/TextObject) | A description of the item. | | [digital](https://schema.org.ai/digital) | [Number](https://schema.org.ai/Number) | Digital maturity score from 0.0 (fully analog/manual) to 1.0 (fully digital/autonomous). Indicates the degree to which an entity operates digitally. | | [disambiguatingDescription](https://schema.org.ai/disambiguatingDescription) | [Text](https://schema.org.ai/Text) | A sub property of description. A short description of the item used to disambiguate from other, similar items. Information from other properties (in particular, name) may be necessary for the description to be useful for disambiguation. | | [identifier](https://schema.org.ai/identifier) | [PropertyValue](https://schema.org.ai/PropertyValue), [Text](https://schema.org.ai/Text), [URL](https://schema.org.ai/URL) | The identifier property represents any kind of identifier for any kind of [Thing](https://schema.org.ai/Thing), such as ISBNs, GTIN codes, UUIDs etc. Schema.org provides dedicated properties for representing many of these, either as textual strings or as URL (URI) links. See [background notes](https://schema.org/docs/datamodel.html#identifierBg) for more details. | | [image](https://schema.org.ai/image) | [ImageObject](https://schema.org.ai/ImageObject), [URL](https://schema.org.ai/URL) | An image of the item. This can be a [URL](https://schema.org.ai/URL) or a fully described [ImageObject](https://schema.org.ai/ImageObject). | | [mainEntityOfPage](https://schema.org.ai/mainEntityOfPage) | [CreativeWork](https://schema.org.ai/CreativeWork), [URL](https://schema.org.ai/URL) | Indicates a page (or other CreativeWork) for which this thing is the main entity being described. See [background notes](https://schema.org/docs/datamodel.html#mainEntityBackground) for details. | | [name](https://schema.org.ai/name) | [Text](https://schema.org.ai/Text) | The name of the item. | | [owner](https://schema.org.ai/owner) | [Organization](https://schema.org.ai/Organization), [Person](https://schema.org.ai/Person) | A person or organization who owns this Thing. | | [potentialAction](https://schema.org.ai/potentialAction) | [Action](https://schema.org.ai/Action) | Indicates a potential Action, which describes an idealized action in which this thing would play an 'object' role. | | [sameAs](https://schema.org.ai/sameAs) | [URL](https://schema.org.ai/URL) | URL of a reference Web page that unambiguously indicates the item's identity. E.g. the URL of the item's Wikipedia page, Wikidata entry, or official website. | | [subjectOf](https://schema.org.ai/subjectOf) | [CreativeWork](https://schema.org.ai/CreativeWork), [Event](https://schema.org.ai/Event) | A CreativeWork or Event about this Thing. | | [url](https://schema.org.ai/url) | [URL](https://schema.org.ai/URL) | URL of the item. | ## Subtypes | Type | Description | |------|-------------| | [StatisticalVariable](https://schema.org.ai/StatisticalVariable) | [StatisticalVariable](https://schema.org.ai/StatisticalVariable) represents any type of statistical metric that can be measured at a place and time. The usage pattern for [StatisticalVariable](https://schema.org.ai/StatisticalVariable) is typically expressed using [Observation](https://schema.org.ai/Observation) with an explicit [populationType](https://schema.org.ai/populationType), which is a type, typically drawn from Schema.org. Each [StatisticalVariable](https://schema.org.ai/StatisticalVariable) is marked as a [ConstraintNode](https://schema.org.ai/ConstraintNode), meaning that some properties (those listed using [constraintProperty](https://schema.org.ai/constraintProperty)) serve in this setting solely to define the statistical variable rather than literally describe a specific person, place or thing. For example, a [StatisticalVariable](https://schema.org.ai/StatisticalVariable) Median\_Height\_Person\_Female representing the median height of women, could be written as follows: the population type is [Person](https://schema.org.ai/Person); the measuredProperty [height](https://schema.org.ai/height); the [statType](https://schema.org.ai/statType) [median](https://schema.org.ai/median); the [gender](https://schema.org.ai/gender) [Female](https://schema.org.ai/Female). It is important to note that there are many kinds of scientific quantitative observation which are not fully, perfectly or unambiguously described following this pattern, or with solely Schema.org terminology. The approach taken here is designed to allow partial, incremental or minimal description of [StatisticalVariables](https://schema.org.ai/StatisticalVariable), and the use of detailed sets of entity and property IDs from external repositories. The [measurementMethod](https://schema.org.ai/measurementMethod), [unitCode](https://schema.org.ai/unitCode) and [unitText](https://schema.org.ai/unitText) properties can also be used to clarify the specific nature and notation of an observed measurement. | --- Quoted from Schema.org 30.1, https://schema.org/ConstraintNode, under CC BY-SA 3.0. Served by the Org.AI Foundation at https://schema.org.ai/ConstraintNode.