WikidataQuality/Constraints

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Constraint Description Needed Entities
{{Constraint:Single value}} used to specify that this property may only be used once per entity

In the list of statements on an entity, there must be only one statement using this property. If there is more than one statement using this property, all of them are individually considered violations. If the statements have qualifiers 'start time', 'end time', 'point in time', all statements that are supposedly true at the same time are individually considered violations.

Item 'Single Value Constraint'
{{Constraint:Unique value}} used to specify that all values for this property differ from each other


In the set of all statements using this property, there must be no duplicate value.
If there is, all statements containing duplicates are individually considered violations.

Item 'Unique Value Constraint'
{{Constraint:Format}} used to specify that the value for this property has to correspond to a given pattern

The given regular expression has to match the string value of this statement.
If it doesn't, this statement is considered a violation.

Item 'Format Constraint'

Property 'Pattern'

{{Constraint:One of}} used to specify that the value for this property has to be one of a given set of items

The item value of this statement has to be included in the given set of items. If it isn't, this statement is considered a violation.

Item 'One Of Constraint'
{{Constraint:Symmetric}} used to specify that the referenced item has to refer back to this item

This statement is defined on one item and has a second item as its value. Therefore, the second item should have a statement with the same property, referencing to the first item. If the second item doesn't have such a statement, the statement on the first item is considered a violation.

Item 'Symmetric Constraint'
{{Constraint:Inverse}} used to specify that the referenced item has to refer back to this item with the given inverse property

This statement is defined on one item and has a second item as its value. Therefore, the second item should have a statement with the given inverse property, referencing to the first item. If the second item doesn't have such a statement, the statement on the first item is considered a violation.

Item 'Inverse Constraint'

Property 'Property'

{{Constraint:Commons link}} used to specify that the value must link to an existing Wikimedia Commons page

The value of this statement should contain a valid link, the link should go to Wikimedia Commons, and the referenced page should exist.

Item 'Commons Link Constraint'

Property 'Namespace'

{{Constraint:Target required claim}} used to specify that the referenced item must have a statement with a given property

The item referenced by this statement is required to have a statement using the given property. If items are given, the statement on the other item has to have one of the items as a value.
If either of the criteria is not fulfilled, this statement is considered a violation.

Item 'Value Requires Claim Constraint'

Properties 'Property', 'Item'

{{Constraint:Item}} used to specify that an item with this statement must have another given property

The item with this statement is required to have another statement using the given property. If items are given, the other statement has to have one of the items as a value.
If either of the criteria is not fulfilled, this statement is considered a violation.

Item 'Requires Claim Constraint'

Properties 'Property', 'Item'

{{Constraint:Type}} used to specify that the item must be a subclass or instance of a given type

The item with this statement requires another statement that if the relation is 'subclass' uses the 'subclass of' property
or if the relation is 'instance' uses the 'instance of' property
and has a value which itself is a subclass of the given class.
If it doesn't, this statement is considered a violation.

Item: 'Type Constraint', 'Subclass Relation', 'Instance Relation'

Properties: 'Relation', 'Class'

{{Constraint:Value type}} used to specify that the referenced item must be a subclass or instance of a given type

The item referenced by this statement requires another statement that if the relation is 'subclass' uses the 'subclass of' property
or if the relation is 'instance' uses the 'instance of' property
and has a value which itself is a subclass of the given class.
If it doesn't, this statement is considered a violation.

Item: 'Value Type Constraint', 'Subclass Relation', 'Instance Relation'

Properties: 'Relation', 'Class'

{{Constraint:Range}} used to specify that the value must be between two given values

The value of this statement must neither be less than min nor more than max. If either of the criteria is not fulfilled, this statement is considered a violation.

Item 'Range Constraint'

Properties 'Minimum', 'Maximum'

{{Constraint:Diff within range}} used to specify that the value of a given statement must only differ in the given way

If the item has another statement with the given property, the value of this statement must neither differ less than min nor more than max from the value of that statement. If either of the criteria is not fulfilled, this statement is considered a violation.

Item 'Difference Within Range Constraint'

Properties 'Minimum', 'Maximum'

{{Constraint:Multi value}} used to specify that a property must have more than one value per entity

In the list of statements on an entity, there must be more than one statement using this property. If there is no more than one statement using this property, it is considered a violation.

Item 'Multi Value Constraint'
{{Constraint:Conflicts with}} used to specify that an item must not have a given statement

The item with this statement is forbidden to have another statement using the given property.
If items are given, the other statement is only not allowed to have any of the items as a value.
If either of the criteria is not fulfilled, this statement is considered a violation.

Item 'Conflicts With Constraint'

Properties 'Property', 'Item'

{{Constraint:Qualifiers}} used to specify that only the listed qualifiers may be used

This property must not be used with other qualifiers than the listed ones. If it is, this statement is considered a violation.

Item 'Allowed Qualifiers Constraint'

Property 'Property'

{{Constraint:Qualifier}} used to specify that a property must only be used as a qualifier

This property must only be used as a qualifier. If it used in a claim, this statement is considered a violation.

Item 'Used As Qualifier Constraint'
{{Constraint: Mandatory qualifiers}} used to specify that all of the listed qualifiers have to be used

This property must be used with the listed qualifiers. If one of the listed qualifiers is missing, this statement is considered a violation.

Item 'Mandatory Qualifiers Constraint'