View source for Help:Property constraints portal

<languages />
[[File:Wikidata_property_constraint_violation.png|thumb|upright=1.7|<translate><!--T:1--> Wikidata property constraint violation report on item page.</translate>]]
<translate>
<!--T:2-->
Property constraints are rules on [[<tvar name="pr">Special:MyLanguage/Help:Properties</tvar>|properties]] that specify how properties should be used. The Wikidata model itself is very flexible: nothing stops you from adding <tvar name="q1">{{Q|Q1}}</tvar> as <tvar name="p6">{{Property|P6}}</tvar>. However, a constraint on the property can tell you that a <tvar name="p6">{{Property|P6}}</tvar> is usually a human.

<!--T:3-->
Constraints are hints, not firm restrictions, and are meant as a help or guidance to the editor. They can have exceptions: for example, the town of <tvar name="Q668224">{{Q|Q668224}}</tvar> had the cat <tvar name="Q7627362">{{Q|Q7627362}}</tvar> as honorary mayor.

<!--T:71-->
Some constraint types, currently {{<tvar name=1>ll|Help:Property constraints portal/One of</tvar>|{{Label|Q21510859||one of}}}} and {{<tvar name=2>ll|Help:Property constraints portal/Qualifiers</tvar>|{{Label|Q21510851||allowed qualifiers}}}}, are also used to {{<tvar name=3>ll|Help:Property constraints portal/Entity suggestions from constraint definitions</tvar>|provide better suggestions}} when editing statements.

<!--T:84-->
Note: Technically a property '''constraint''' is a statement (on a property) of a particular '''constraint type''', specified via <tvar name=P2302>{{P|P2302}}</tvar>. So strictly speaking ''constraint'' and ''constraint type'' refer to two different things, for the sake of brevity this page however sometimes refers to ''constraint types'' simply as ''constraints''.
</translate>

{{anchor|Popular constraints}}
<translate>
== Popular constraint types == <!--T:25-->
</translate>
{| class="wikitable"
|+
! {{ucfirst:{{i18n|item}}}}
! <translate><!--T:28--> Help page</translate>
! <translate><!--T:29--> Violation message</translate>
|-
|{{Q|Q19474404}}
|{{ll|Help:Property constraints portal/Single value}}
|[[MediaWiki:Wbqc-violation-message-single-value]]
|-
|{{Q|Q21502410}}
|{{ll|Help:Property constraints portal/Unique value}}
|
|-
|{{Q|Q21502404}}
|{{ll|Help:Property constraints portal/Format}}
|
|-
|{{Q|Q21503250}}
|{{ll|Help:Property constraints portal/Type}}
|
|-
|{{Q|Q21510865}}
|{{ll|Help:Property constraints portal/Value type}}
|
|-
|{{Q|Q21510857}}
|{{ll|Help:Property_constraints_portal/Multi_value}}
|[[MediaWiki:wbqc-violation-message-multi-value]]
|}

* [https://query.wikidata.org/#%23%20https%3A%2F%2Fwww.wikidata.org%2Fwiki%2FHelp%3AProperty_constraints_portal%0A%23%20popular%20contraints%0ASELECT%20%3Fconstraint%20%3FconstraintLabel%20%3Fct%0AWHERE%0A%7B%0A%20%20%7B%0A%20%20SELECT%20%3Fconstraint%20%28count%28%2a%29%20as%20%3Fct%29%0A%20%20WHERE%0A%20%20%7B%0A%20%20%20%20%3Fitem%20wdt%3AP2302%20%3Fconstraint%0A%20%20%7D%0A%20%20GROUP%20BY%20%3Fconstraint%0A%20%20%7D%0A%20%20SERVICE%20wikibase%3Alabel%20%7B%20bd%3AserviceParam%20wikibase%3Alanguage%20%22%5BAUTO_LANGUAGE%5D%2Cen%22.%20%7D%0A%7D%0AORDER%20BY%20DESC%28%3Fct%29%20ASC%28%3Fconstraint%29 <translate><!--T:26--> up-to-date list</translate>]
* [[Wikidata:WikiProject Properties/Reports/Datatypes|<translate><!--T:27--> list of datatypes and applicable value constraints</translate>]]

<translate>
== Datatype-independent constraints == <!--T:85-->
</translate>

<translate>
=== Constraints to restrict where a property may be added === <!--T:86-->
</translate>

; [[Special:MyLanguage/Help:Property constraints portal/Scope|{{Label|Q53869507||property scope}}]]: <translate><!--T:70--> This property should only be used for certain scopes (main value of a statement, in a reference, as qualifier).</translate>
; [[Special:MyLanguage/Help:Property constraints portal/Allowed entity types|{{Label|Q52004125||Allowed entity types}}]]: <translate><!--T:67--> This property should only be used on certain entity types. Example: <tvar name="p1855">{{P|P1855}}</tvar> (properties).</translate>
; [[Special:MyLanguage/Help:Property constraints portal/Type|{{Label|Q21503250||type}}]]: <translate><!--T:50--> Items with this property should have a certain type. Example: Items with {{P|P569}} should be {{P|P31}} {{Q|Q5}} or {{Q|Q729}}.</translate>
; [[Special:MyLanguage/Help:Property constraints portal/Conflicts with|{{Label|Q21502838||conflicts with}}]]: <translate><!--T:34--> Items with this property should not have certain other properties or statements. Examples: {{P|P21}} conflicts with {{P|P50}}, which in turn conflicts with {{St||P31|Q5}}.</translate>
; [[Special:MyLanguage/Help:Property constraints portal/Item|{{Label|Q21503247||item requires claim}}]]: <translate><!--T:39--> Items using this property should also have certain other statements. For example, items with {{P|P157}} should have <tvar name="p20">{{P|P20}}</tvar>, <tvar name="p570">{{P|P570}}</tvar> and <tvar name="stmt">{{St||P1196|Q149086}}</tvar>.</translate>
; [[Special:MyLanguage/Help:Property constraints portal/Contemporary|{{Label|Q25796498||contemporary}}]]: <translate><!--T:35--> Items with this property and values for this property should coexist at some point in time. Examples: {{P|P25}}, {{P|P27}}.</translate>
; [[Special:MyLanguage/Help:Property constraints portal/Label in language|{{Label|Q108139345||label in language}}]]: <translate><!--T:82--> Items using this property should also have a label in a certain language. For example, items with <tvar name="1">{{P|P8500}}</tvar> should have a Vietnamese label.</translate>
; [[Special:MyLanguage/Help:Property constraints portal/Description in language|{{Label|Q111204896||description in language}}]]: <translate><!--T:100--> Items using this property should also have a description in a certain language.</translate>
; [[Special:MyLanguage/Help:Property constraints portal/Lexeme language|{{Label|Q55819106||lexeme language}}]]: <translate><!--T:83--> This property should be used on lexemes in a certain language. For example, <tvar name="1">{{P|P1296}}</tvar> should be used on <tvar name="2">{{Q|Q7026}}</tvar> lexemes.</translate>
; [[Special:MyLanguage/Help:Property constraints portal/Lexeme requires lexical category|{{Label|Q55819078||lexeme requires lexical category}}]]: …
; [[Special:MyLanguage/Help:Property constraints portal/Lexeme value requires lexical category|{{Label|Q64006792||lexeme value requires lexical category}}]]: …

<translate>

=== Constraints regarding the number of values === <!--T:87-->
</translate>

; [[Special:MyLanguage/Help:Property constraints portal/Single value|{{Label|Q19474404||single value}}]]: <translate><!--T:46--> Items should have no more than one statement with this property. Often used for identifiers, but also many other properties: for example, people generally only have a single {{P|P19}} and {{P|P20}}.</translate>
; [[Special:MyLanguage/Help:Property constraints portal/Single best value|{{Label|Q52060874||single best value}}]]: <translate><!--T:62--> Items should have one “best” statement with this property. Often used for properties that can change over time: for example, cities and countries usually have a single <em>current</em> {{P|P6}}.</translate>
; [[Special:MyLanguage/Help:Property constraints portal/Multi value|{{Label|Q21510857||multi value}}]]: <translate><!--T:41--> Items should have more than one statement with this property (or none). Rarely used, but examples include {{P|P161}}, {{P|P3103}} and {{P|P3161}}.</translate>
; [[Special:MyLanguage/Help:Property constraints portal/Unique value|{{Label|Q21502410||unique value}}]]: <translate><!--T:51--> aka. '''unique value''' and '''distinct value'''. No two items should share a value for this property; each item’s value should be unique across all statements for this property in all of Wikidata. Almost all identifier properties have this constraint, since an identifier (ISBN, freebase ID, …) should uniquely identify an entity. Other examples include {{P|P163}} and {{P|P85}}.</translate><!-- TODO: this got rather long and should probably mostly be moved to the subpage. -->

<translate>
=== Constraints regarding qualifiers === <!--T:88-->
</translate>

; [[Special:MyLanguage/Help:Property constraints portal/Qualifiers|{{Label|Q21510851||allowed qualifiers}}]]: <translate><!--T:44--> Statements for this property should not have any qualifiers other than the listed ones. Examples: {{P|P30}} with qualifiers {{P|P580}} and {{P|P582}}, and {{P|P646}} with no qualifiers at all.</translate>
; [[Special:MyLanguage/Help:Property constraints portal/Mandatory qualifiers|{{Label|Q21510856||mandatory qualifiers}}]]: <translate><!--T:40--> Statements for this property must have all of the listed qualifiers. Example: {{P|P414}} with {{P|P249}} and {{P|P580}}.</translate>

<translate>
=== Constraints regarding references === <!--T:89-->
</translate>

; [[Special:MyLanguage/Help:Property constraints portal/Citation needed|{{Label|Q54554025||citation needed constraint}}]]: <translate><!--T:69--> Statements for this property should have at least one reference. Example: [[<tvar name="challenged-properties">Wikidata:WikiProject Properties/Wikidata properties likely to be challenged</tvar>|properties likely to be challenged]].</translate>

<translate>
== Datatype-specific constraints == <!--T:90-->
</translate>

<translate>
=== Constraints for datatype item/entity === <!--T:91-->
</translate>

; [[Special:MyLanguage/Help:Property constraints portal/Value type|{{Label|Q21510865||value type}}]]: <translate><!--T:59--> Values for this property should have a certain type. Example: {{P|25}} should be {{P|P31}} {{Q|Q5}} or {{Q|Q729}}.</translate>
; [[Special:MyLanguage/Help:Property constraints portal/One of|{{Label|Q21510859||one of}}]]: <translate><!--T:42--> Values for this property should be one of a given set of items. Example: {{P|1622}} should be either {{Q|Q13196750}} or {{Q|Q14565199}}.</translate>
; [[Special:MyLanguage/Help:Property constraints portal/None of|{{Label|Q52558054||none of}}]]: <translate><!--T:68--> Values for this property should not be one of a given set of items. Example: <tvar name="p31">{{P|P31}}</tvar> should not be <tvar name="q467">{{Q|Q467}}</tvar>.</translate>
; [[Special:MyLanguage/Help:Property constraints portal/Target required claim|{{Label|Q21510864||target required statement}}]]: <translate><!--T:49--> aka. '''target required statement'''. Values for this property should also have certain other statements. For example, {{P|P58}} values should have {{P|P21}} and {{St||P106|Q28389}}.</translate>
; [[Special:MyLanguage/Help:Property constraints portal/Symmetric|{{Label|Q21510862||symmetric}}]]: <translate><!--T:48--> Statements using this property should always exist in both directions. Examples: {{P|P3373}}, {{P|P190}}.</translate>
; [[Special:MyLanguage/Help:Property constraints portal/Inverse|{{Label|Q21510855||inverse}}]]: <translate><!--T:66--> Statements using this property should always have an inverse statement. Examples: <tvar name="p22">{{P|P22}}</tvar>/<tvar name="p25">{{P|P25}}</tvar> with <tvar name="p40">{{P|P40}}</tvar>.</translate>
; {{ll|Help:Property constraints portal/Value label|{{Label|Q100884525}} }}
: <translate><!--T:99--> Values for this property have to have a label in a specific language that matches a specific format.</translate>

=== <translate><!--T:92--> Constraints for <tvar name="1">{{int:wikibase-listdatatypes-quantity-head}}</tvar></translate> ===

; [[Special:MyLanguage/Help:Property constraints portal/Integer|{{Label|Q52848401||integer}}]]: <translate><!--T:65--> Values for this property should be integers without decimal places.</translate>
; [[Special:MyLanguage/Help:Property constraints portal/Units|{{Label|Q21514353||units}}]]: <translate><!--T:53--> Values for this statement should only use certain units (or none). Examples: {{P|P2097}} (unit: {{Q|Q577}}), {{P|P1082}} (no units).</translate>
; [[Special:MyLanguage/Help:Property constraints portal/No bounds|{{Label|Q51723761||no bounds}}]]: <translate><!--T:61--> Values for this property should not use upper and lower bounds. This applies to most non-physical properties with ''quantity'' data type, for which the concept of uncertainties is not defined.</translate>
; [[Special:MyLanguage/Help:Property constraints portal/Range|{{Label|Q21510860||range}}]]: <translate><!--T:45--> Values for this property should be within a certain range or interval. Examples: {{P|P1102}} is always between 0 and 1, and {{P|P619}} should not be before {{ISOdate|1957-10-04}}.</translate>
; [[Special:MyLanguage/Help:Property constraints portal/Diff within range|{{Label|Q21510854||diff within range}}]]: <translate><!--T:36--> aka. '''difference within range'''. The difference between values for this property and for another property should be within a certain range or interval. For example, the difference between {{P|P569}} and {{P|P570}} should be between 0 and 150 years.</translate>

=== <translate><!--T:93--> Constraints for <tvar name="1">{{int:wikibase-listdatatypes-time-head}}</tvar></translate> ===

; [[Special:MyLanguage/Help:Property constraints portal/Range|{{Label|Q21510860||range}}]]: <translate><!--T:94--> Values for this property should be within a certain range or interval. Examples: {{P|P1102}} is always between 0 and 1, and {{P|P619}} should not be before {{ISOdate|1957-10-04}}.</translate>
; [[Special:MyLanguage/Help:Property constraints portal/Diff within range|{{Label|Q21510854||diff within range}}]]: <translate><!--T:95--> aka. '''difference within range'''. The difference between values for this property and for another property should be within a certain range or interval. For example, the difference between {{P|P569}} and {{P|P570}} should be between 0 and 150 years.</translate>

<translate>
=== Constraints for string-based datatypes === <!--T:96-->
</translate>

<translate>
<!--T:97-->
The constraint types listed in this section can be used for properties that have a {{ll|<tvar name="string-based">Help:Data type#string-based</tvar>|string-based datatype}}.
</translate>

; [[Special:MyLanguage/Help:Property constraints portal/Format|{{Label|Q21502404||format}}]]: <translate><!--T:38--> Values for this property should have a certain format. Often used for identifiers (''n'' digits long, starts with a certain letter, consists of digits, …).</translate>

<translate>
=== Constraints for Commons links === <!--T:98-->
</translate>

; [[Special:MyLanguage/Help:Property constraints portal/Commons link|{{Label|Q21510852||commons link constraint}}]]: <translate><!--T:33--> Values for this statement should be valid links to Wikimedia Commons. Examples: {{P|P18}} (“File” namespace), {{P|P373}} (“Category” namespace).</translate>

<translate>
== Constraints alphabetically == <!--T:4-->
</translate>

* [https://query.wikidata.org/#select%20%3Flabelen%20%3Fconstrainttype%20%3FconstrainttypeLabel%20%3FconstrainttypeDescription%20%7B%0A%20%20%3Fconstrainttype%20wdt%3AP279%2a%20wd%3AQ21502402%20.%0A%20%20SERVICE%20wikibase%3Alabel%20%7B%20bd%3AserviceParam%20wikibase%3Alanguage%20%22%5BAUTO_LANGUAGE%5D%2Cen%22.%20%7D%0A%20%20optional%20%7B%20%3Fconstrainttype%20rdfs%3Alabel%20%3Flabelen%20filter%28lang%28%3Flabelen%29%20%3D%20%22en%22%29%20.%20%7D%0A%7D%20order%20by%20%3Flabelen <translate><!--T:60--> A table that shows the list of constraint in the query service in your language, augmented with the English label if you need this in a discussion in English</translate>]

<translate>
<!--T:7-->
Several constraints have their own predefined templates and are listed at <tvar name="help-pc-list">{{ll|Help:Property constraints/list of constraints}}</tvar>.

== Usage instructions == <!--T:8-->

<!--T:63-->
Constraint reports are shown for all logged in users when they visit an entity page.</translate>

[[File:Douglas_Adams_Constraint_Violation.png|center|thumb|upright=1.5|<translate><!--T:64--> A constraint violation report displayed on an item page.</translate>]]

<translate><!--T:12-->
You can also check all constraints for an item on [[Special:ConstraintReport]]. This page is provided by [[mw:Extension:WikibaseQualityConstraints|WikibaseQualityConstraints]] (also known as "constraints extension"). A bot also maintains reports of constraint violation; see a summary of violations across Wikidata on [[Wikidata:Database reports/Constraint violations]].</translate>

{{Anchor|constraint-type-items}}
<translate>
== Constraint type items == <!--T:14-->

<!--T:15-->
There is an item for each constraint type, e.g. <tvar name="q">{{Q|Q21503250}}</tvar>.

== Constraint statements on properties == <!--T:16-->

<!--T:17-->
Constraints for a property are specified as statements on the property, using <tvar name="p2302">{{P|P2302}}</tvar> and the [[<tvar name="item">#constraint-type-items</tvar>|constraint type item]].
For example: <tvar name="example">{{St|{{P|3373}}|P2302|Q21510862}}</tvar>.
Deprecated statements are ignored, so changing a constraint statement’s rank to “deprecated” is a convenient way to temporarily disable a constraint without completely removing it.

=== Constraint parameters === <!--T:18-->

<!--T:19-->
Many constraints are configurable: '''one of''' has a list of the permitted values, '''type''' contains the type, etc.
These settings which configure the constraint are called ''parameters''.

<!--T:20-->
Constraint parameters are specified as qualifiers on the statement.
For example:</translate>
{{C|{{P|P25}}|P2302|Q21503250|P2309|Q21503252|P2308|Q5}}

<translate><!--T:21-->
There are several general parameters that can be added to any constraint statement:</translate>

; <translate><!--T:22--> <tvar name="P2316">{{P|P2316}}</tvar>: With the value <tvar name="Q21502408">{{Q|Q21502408}}</tvar>, this parameter can be used to mark a constraint as ''mandatory''. Violations of mandatory constraints are more severe than violations of non-mandatory ones. Non-mandatory constraints should have a value of <tvar name="Q62026391">{{Q|Q62026391}}</tvar>.</translate>
; <translate><!--T:72--> <tvar name="P2303">{{P|P2303}}</tvar>: Lists known exceptions to the constraint. On the items listed under this parameter, the constraint is not checked.</translate>
; <translate><!--T:73--> <tvar name="P2304">{{P|P2304}}</tvar>: Contains a property by the values of which constraint violations should be grouped. That is, when the [[<tvar name="db-rep">Wikidata:Database reports/Constraint violations</tvar>|database reports]] list violations for a constraint (for all items), the items with violations are grouped by the value they have for the property given in the <tvar name="P2304">{{P|P2304}}</tvar> parameter. (The constraints extension does not use this parameter.)</translate>
; <translate><!--T:74--> <tvar name="P4680">{{P|P4680}}</tvar>: Specifies in which part of a statement the constraints applies, using the three special values <tvar name="Q46466787">{{Q|Q46466787}}</tvar>, <tvar name="Q46466783">{{Q|Q46466783}}</tvar> and <tvar name="Q46466805">{{Q|Q46466805}}</tvar>. Use any combination of these values to specify where a constraint should be checked. If the parameter is not specified, the default scope depends on the constraint type. (Note that the [[<tvar name="db-rep">Wikidata:Database reports/Constraint violations</tvar>|database reports]] only list violations on the main value of a statement.)</translate>
; <translate><!--T:75--> <tvar name="P6607">{{P|P6607}}</tvar>: Provides a simple explanation for the purpose of the constraint (why it exists) and recommended actions to resolve the constraint.</translate>

<translate>

== When constraints aren’t checked == <!--T:78-->

<!--T:79-->
Each individual constraint can list exceptions in its constraint parameters (see above); on any statements of that item, that constraint will not be checked at all. (There is currently no mechanism for specifying other entity types as exceptions, or for listing exceptions in a different way.)

<!--T:80-->
On properties like <tvar name=1>{{P|P1855}}</tvar>, <tvar name=2>{{P|P2271}}</tvar>, etc., as defined in <tvar name="3"><code>wgWBQualityConstraintsPropertiesWithViolatingQualifiers</code></tvar>, all constraint checks on qualifiers are skipped. For these properties, qualifiers have a different meaning than usual: they’re more similar to main statements than qualifiers of that statement, so it doesn’t really make sense to check constraints on those qualifiers. 

<!--T:81-->
WikibaseQualityConstraints only uses normal-rank and preferred-rank constraint statements and ignores deprecated-rank ones, so setting a constraint’s rank to deprecated can be used to “hide” it from WikibaseQualityConstraints. 
(KrBot uses all constraint statements regardless of rank.)

==Custom constraints== <!--T:23-->

<!--T:24-->
With some knowledge of [[<tvar name="wd-sparql">Special:MyLanguage/Wikidata:SPARQL query service</tvar>|SPARQL]]  one can make very complex constraints for certain properties, above and beyond the restrictions mentioned above. More information is available at <tvar name="tpl-cc">[[Template:Complex constraint]]</tvar>. The reports are maintained by a third-party bot and not part of Wikibase software. See also the list of [<tvar name="links-to-tpl-cc">https://www.wikidata.org/w/index.php?title=Special%3AWhatLinksHere&target=Template%3AComplex+constraint&namespace=121</tvar> properties using complex constraints].

==See also== <!--T:76-->

<!--T:77-->
* [[Wikidata:Curious Facts]] - a tool that displays random constraint violations</translate>

{{Property constraints}}
{{Translation categories|category=Help:Properties}}