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{{Short description|Free knowledge database project}}
{{for|Wikipedia's information page on Wikidata|Wikipedia:Wikidata|selfref=true}}
{{Multiple issues|
{{Primary sources|date=December 2020}}
{{Update|part=Screenshots; and more|date=June 2025}}
}}
{{Use dmy dates|date=January 2021}}
{{Infobox website
| logo = Wikidata-logo-en.svg
| logo_alt = Logo of Wikidata, a bar code with red, green, and blue stripes
| collapsible = yes
| screenshot = Wikidata main page screenshot.png
| caption = Main page of Wikidata in April 2021
| url = {{Official URL}} {{Wikidata|references|linked|P407}}
| commercial = No
| type = {{hlist|class=nowrap |[[Knowledge base]] |[[Wiki]]}}
| registration = Optional
| language = Multiple languages
| owner = [[Wikimedia Foundation]]
| editor = {{Wikidata|properties|linked|references|linked|P50}}
| author =
| name = Wikidata
| location =
| launch_date = {{start date and age|2012|10|29|df=y}}{{Wikidata|references|P571}}
}}

'''Wikidata''' is a [[Wiki|collaboratively edited]] multilingual [[knowledge graph]] hosted by the [[Wikimedia Foundation]].<ref>{{Cite news|last=Chalabi|first=Mona|date=April 26, 2013|title=Welcome to Wikidata! Now what?|url=https://www.theguardian.com/news/datablog/2013/apr/26/wikidata-launch|access-date=October 2, 2021|archive-date=2 October 2021|archive-url=https://web.archive.org/web/20211002152920/https://www.theguardian.com/news/datablog/2013/apr/26/wikidata-launch|url-status=live}}</ref> It is a common source of [[open data]] that Wikimedia projects such as [[Wikipedia]],<ref name="Wikidata Main Page archive"/><ref>{{cite web |url=http://www.wikimedia.de/wiki/Pressemitteilungen/PM_3_12_Wikidata_EN |title=Data Revolution for Wikipedia |date=March 30, 2012 |publisher=Wikimedia Deutschland |access-date=September 11, 2012 |archive-url=https://web.archive.org/web/20121023170149/http://www.wikimedia.de/wiki/Pressemitteilungen/PM_3_12_Wikidata_EN |archive-date=October 23, 2012 |url-status=live}}</ref> and anyone else, are able to use under the [[CC0]] [[public domain]] license. Wikidata is a wiki powered by the software [[MediaWiki]], including its extension for [[semi-structured data]], the [[Wikibase]]. As of early 2025, Wikidata had 1.65 billion item statements ([[semantic triple]]s).<ref>{{Cite web |title=Grafana |url=https://grafana.wikimedia.org/d/000000175/wikidata-datamodel-statements?orgId=1&refresh=30m |access-date=2024-03-21 |website=grafana.wikimedia.org}}</ref>

== Concept ==
[[File:Datamodel in Wikidata.svg|thumb|upright=2.74|center|{{center|This diagram shows the most important terms used in Wikidata.}}]]

Wikidata is a [[document-oriented database]], focusing on ''items'', which represent any kind of topic, concept, or object. Each item is allocated a unique [[persistent identifier]] called its ''QID'', a positive integer prefixed with the upper-case letter "Q"{{efn|Q is the first initial of Qamarniso Vrandečić (née Ismoilova), an Uzbek Wikimedian married to Wikidata co-developer [[Denny Vrandečić]].<ref>{{cite book |last1=Vrandečić |first1=Denny |last2=Pintscher |first2=Lydia |last3=Krötzsch |first3=Markus |title=Companion Proceedings of the ACM Web Conference 2023 |chapter=Wikidata: The Making of |date=30 April 2023 |pages=615–624 |chapter-url=https://dl.acm.org/doi/10.1145/3543873.3585579 |doi=10.1145/3543873.3585579|isbn=9781450394192 |s2cid=258377705 }}</ref>}}. This makes it possible to provide translations of the basic information describing the topic each item covers without favouring any particular language.

Some examples of items and their QIDs are {{Wikidata entity link|Q8470}}, {{Wikidata entity link|Q316}}, {{Wikidata entity link|Q42775}}, {{Wikidata entity link|Q303}}, and {{Wikidata entity link|Q36611}}.

Item ''labels'' do not need to be unique. For example, there are two items named "Elvis Presley": {{Wikidata entity link|Q303}}, which represents [[Elvis Presley|the American singer and actor]], and {{Wikidata entity link|Q610926}}, which represents his [[Elvis Presley (album)|self-titled album]]. However, the combination of a label and its ''description'' must be unique. To avoid ambiguity, an item's QID is hence linked to this combination.

=== Main parts ===
[[File:Wikidata layout Phase I.png|alt=Wikidata screenshot|center|700px|thumb|<br /><br />A layout of the four main components of a phase-1 Wikidata page: the label, description, aliases, and interlanguage links]]

Fundamentally, an item consists of:

* An [[identifier]] (the QID), related to a label and a description.
* Optionally, multiple aliases and some number of statements (and their properties and values).

=== Statements ===
[[Image:Wikidata statements Mars.png|alt=Wikidata screenshot|thumb|700px|center|Three statements from [[Wikidata:Q111|Wikidata's item on the planet Mars]] (Q111). Values include links to other items and to [[Wikimedia Commons]].]]

''Statements'' are how any information known about an item is recorded in Wikidata. Formally, they consist of [[attribute–value pair|key–value pairs]], which match a ''property'' (such as "author", or "publication date") with one or more entity ''values'' (such as "[[Sir Arthur Conan Doyle]]" or "1902"). For example, the informal English statement "milk is white" would be encoded by a statement pairing the property {{Wikidata entity link|P462}} with the value {{Wikidata entity link|Q23444}} under the item {{Wikidata entity link|Q8495}}.

Statements may map a property to more than one value. For example, the "occupation" property for [[Marie Curie]] could be linked with the values "physicist" and "chemist", to reflect the fact that she engaged in both occupations.<ref>{{cite web|url=https://www.wikidata.org/wiki/Help:Statements|title=Help:Statements – Wikidata|website=www.wikidata.org|access-date=20 February 2019|archive-date=25 March 2019|archive-url=https://web.archive.org/web/20190325054926/https://www.wikidata.org/wiki/Help:Statements|url-status=live}}</ref>

Values may take on many types including other Wikidata items, strings, numbers, or media files. Properties prescribe what types of values they may be paired with. For example, the property {{Wikidata entity link|P856}} may only be paired with values of type "URL".<ref>{{cite web|url=https://www.wikidata.org/wiki/Help:Data_type|title=Help:Data type – Wikidata|website=www.wikidata.org|access-date=20 February 2019|archive-date=23 March 2019|archive-url=https://web.archive.org/web/20190323184623/https://www.wikidata.org/wiki/Help:Data_type|url-status=live}}</ref>

Optionally, ''qualifiers'' can be used to refine the meaning of a statement by providing additional information. For example, a "population" statement could be modified with a qualifier such as "point in time (P585): 2011" (as its own key-value pair). Values in the statements may also be annotated with ''references'', pointing to a source backing up the statement's content.<ref>{{cite web|url=https://www.wikidata.org/wiki/Help:Sources|title=Help:Sources – Wikidata|website=www.wikidata.org|access-date=20 February 2019|archive-date=17 April 2019|archive-url=https://web.archive.org/web/20190417231251/https://www.wikidata.org/wiki/Help:Sources|url-status=live}}</ref> As with statements, all qualifiers and references are property–value pairs.

=== Properties ===
[[File:Wikidata - simple statement.svg|thumb|center|500px|Example of a simple statement consisting of one property–value pair]]

Each property has a numeric identifier prefixed with a capital P and a page on Wikidata with optional label, description, aliases, and statements. As such, there are properties with the sole purpose of describing other properties, such as {{Wikidata entity link|P1647}}.

Properties may also define more complex rules about their intended usage, termed ''constraints''. For example, the {{Wikidata entity link|P36}} property includes a "single value constraint", reflecting the reality that (typically) territories have only one capital city. Constraints are treated as testing alerts and hints, rather than inviolable rules.<ref>{{cite web|url=https://www.wikidata.org/wiki/Help:Property_constraints_portal|title=Help:Property constraints portal|website=Wikidata|access-date=20 February 2019|archive-date=1 June 2019|archive-url=https://web.archive.org/web/20190601180538/https://www.wikidata.org/wiki/Help:Property_constraints_portal|url-status=live}}</ref>

Before a new property is created, it needs to undergo a discussion process.<ref>{{cite web|url=https://openpreservation.org/blogs/wikidata-as-a-digital-preservation-knowledgebase/|title=Wikidata as a digital preservation knowledgebase|last=Cochrane|first=Euan|date=30 September 2016|website=openpreservation.org|access-date=5 January 2022|archive-date=5 January 2022|archive-url=https://web.archive.org/web/20220105110113/https://openpreservation.org/blogs/wikidata-as-a-digital-preservation-knowledgebase/|url-status=live}}</ref><ref>{{cite conference |last=Samuel |first=John |title=Experimental IR Meets Multilinguality, Multimodality, and Interaction |chapter=Analyzing and Visualizing Translation Patterns of Wikidata Properties |series=Lecture Notes in Computer Science |book-title=Experimental IR Meets Multilinguality, Multimodality, and Interaction |conference=[[Conference and Labs of the Evaluation Forum|CLEF]] 2018 |date=15 August 2018 |volume=11018 |page=129 |doi=10.1007/978-3-319-98932-7_12 |isbn=978-3-319-98931-0 |chapter-url=https://books.google.com/books?id=hD5qDwAAQBAJ&pg=PA129}}</ref>

The most used property is {{Wikidata entity link|P2860}}, which is used on more than {{formatnum:290000000}} item pages {{as of|2023|11|lc=y|post=.}}<ref>{{cite web|url=https://www.wikidata.org/wiki/Wikidata:Database_reports/List_of_properties/Top100|title=Wikidata:Database reports/List of properties/Top100|accessdate=18 November 2023|archive-date=24 February 2023|archive-url=https://web.archive.org/web/20230224212120/https://www.wikidata.org/wiki/Wikidata:Database_reports/List_of_properties/Top100|url-status=live}}</ref>

=== Lexemes ===
[[File:L34909 tlhIngan wo' – Lexeme on Wikidata.png|thumb|left|208x208px|Wikidata Klingon [[wikidata:Lexeme:L34909|lexeme entry]]]]In [[linguistics]], a [[lexeme]] is a unit of [[Lexical semantics|lexical]] meaning representing a group of words that share the same core meaning and grammatical characteristics.<ref>{{Citation |last=Andreou |first=Marios |title=Lexemes |date=2019-03-27 |work=Linguistics |url=https://oxfordbibliographies.com/view/document/obo-9780199772810/obo-9780199772810-0232.xml |access-date=2024-08-17 |publisher=Oxford University Press |language=en |doi=10.1093/obo/9780199772810-0232 |isbn=978-0-19-977281-0|doi-access=free |url-access=subscription }}</ref><ref>{{Cite book |last1=Bonami |first1=Olivier |url=https://zenodo.org/record/1402520 |title=The Lexeme In Descriptive And Theoretical Morphology |last2=Boyé |first2=Gilles |last3=Dal |first3=Georgette |last4=Giraudo |first4=Hélène |last5=Namer |first5=Fiammetta |date=2018-08-23 |publisher=[[Language Science Press]] |doi=10.5281/zenodo.1402520}}</ref> Similarly, Wikidata's ''lexemes'' are items with a structure that makes them more suitable to store [[Lexicography|lexicographical]] data. Since 2016, Wikidata has supported lexicographical entries in the form of lexemes.<ref>{{Citation |last=Nielsen |first=Finn Årup |title=Ordia: A Web Application for Wikidata Lexemes |date=2019 |work=The Semantic Web: ESWC 2019 Satellite Events |series=Lecture Notes in Computer Science |volume=11762 |pages=141–146 |editor-last=Hitzler |editor-first=Pascal |url=http://link.springer.com/10.1007/978-3-030-32327-1_28 |access-date=2024-08-17 |place=Cham |publisher=Springer International Publishing |language=en |doi=10.1007/978-3-030-32327-1_28 |isbn=978-3-030-32326-4 |editor2-last=Kirrane |editor2-first=Sabrina |editor3-last=Hartig |editor3-first=Olaf |editor4-last=de Boer |editor4-first=Victor|url-access=subscription }}</ref>

In Wikidata, lexicographical entries have a different identifier from regular item entries. These entries are prefixed with the letter L, such as in the example entries for [[wikidata:Lexeme:L16168|book]] and [[wikidata:Lexeme:L3726|cow]]. Lexicographical entries in Wikidata can contain statements, senses, and forms.<ref>{{cite web |title=Wikidata:Lexicographical data/Documentation – Wikidata |url=https://www.wikidata.org/wiki/Wikidata:Lexicographical_data/Documentation |url-status=live |archive-url=https://web.archive.org/web/20181113210533/https://www.wikidata.org/wiki/Wikidata:Lexicographical_data/Documentation |archive-date=13 November 2018 |access-date=13 November 2018 |website=www.wikidata.org}}</ref> The use of lexicographical entries in Wikidata allows for the documentation of word usage, the connection between words and items on Wikidata, word translations, and enables machine-readable lexicographical data.

In 2020, lexicographical entries on Wikidata exceeded 250,000. The language with the most lexicographical entries was [[Russian language|Russian]], with a total of 101,137 lexemes, followed by [[English language|English]] with 38,122 lexemes. There are over 668 languages with lexicographical entries on Wikidata.<ref>{{Cite journal |last=Nielsen |first=Finn |orig-date=2020-05 |editor-last=Ionov |editor-first=Maxim |editor2-last=McCrae |editor2-first=John P. |editor3-last=Chiarcos |editor3-first=Christian |editor4-last=Declerck |editor4-first=Thierry |editor5-last=Bosque-Gil |editor5-first=Julia |editor6-last=Gracia |editor6-first=Jorge |title=Lexemes in Wikidata: 2020 status |url=https://aclanthology.org/2020.ldl-1.12/ |journal=Proceedings of the 7th Workshop on Linked Data in Linguistics (LDL-2020) |date=May 2020 |language=English |location=Marseille, France |publisher=European Language Resources Association |pages=82–86 |isbn=979-10-95546-36-8}}</ref>

=== Entity schemas ===
[[File:Bagian Wikidata - Skema Entitas.svg|thumb|275x275px|[[wikidata:EntitySchema:E10|Human entity schema]] in Wikidata]]
In Wikidata, a schema is a data model that outlines the necessary attributes for a data item.<ref name=":0">{{Cite book |last=Werkmeister |first=Lucas |url=https://www.fiz-karlsruhe.de/sites/default/files/FIZ/Dokumente/Forschung/ISE/Masterarbeiten/master-thesis-Lucas-Werkmeister.pdf |title=Schema Inference of Wikidata |date=2018 |publisher=Fakultät für Informatik, [[Karlsruhe Institute of Technology]] |location=Karlsruhe |language=en-GB}}</ref><ref>Hernández, Daniel; Hogan, Aidan; Krötzsch, M. (2015). "[https://www.semanticscholar.org/paper/Reifying-RDF%3A-What-Works-Well-With-Wikidata-Hern%C3%A1ndez-Hogan/07b520b6ee7b86caa4331cd5365708f6a9647592 Reifying RDF: What Works Well With Wikidata?]".</ref> For instance, a data item that uses the attribute "[[wikidata:Property:P31|instance of]]" with the value "[[wikidata:Q5|human]]" would typically include attributes such as "[[wikidata:Property:P19|place of birth]]," "[[wikidata:Property:P569|date of birth]]," [[wikidata:Property:P570|"date of death]]," and "[[wikidata:Property:P20|place of death]]."<ref>{{Citation |last1=Erxleben |first1=Fredo |title=Introducing Wikidata to the Linked Data Web |date=2014 |work=Lecture Notes in Computer Science |pages=50–65 |url=http://dx.doi.org/10.1007/978-3-319-11964-9_4 |access-date=2024-08-18 |place=Cham |publisher=Springer International Publishing |isbn=978-3-319-11963-2 |last2=Günther |first2=Michael |last3=Krötzsch |first3=Markus |last4=Mendez |first4=Julian |last5=Vrandečić |first5=Denny|doi=10.1007/978-3-319-11964-9_4 |url-access=subscription }}</ref> The entity schema in Wikidata utilizes [[ShEx|Shape Expression]] (ShEx) to describe the data in Wikidata items in the form of a [[Resource Description Framework]] (RDF).<ref>{{Citation |last1=Thornton |first1=Katherine |title=Using Shape Expressions (ShEx) to Share RDF Data Models and to Guide Curation with Rigorous Validation |date=2019 |work=The Semantic Web |volume=11503 |pages=606–620 |editor-last=Hitzler |editor-first=Pascal |place=Cham |publisher=Springer International Publishing |language=en |doi=10.1007/978-3-030-21348-0_39 |isbn=978-3-030-21347-3 |last2=Solbrig |first2=Harold |last3=Stupp |first3=Gregory S. |last4=Labra Gayo |first4=Jose Emilio |last5=Mietchen |first5=Daniel |last6=Prud’hommeaux |first6=Eric |last7=Waagmeester |first7=Andra |editor2-last=Fernández |editor2-first=Miriam |editor3-last=Janowicz |editor3-first=Krzysztof |editor4-last=Zaveri |editor4-first=Amrapali|doi-access=free |hdl=10651/53418 |hdl-access=free }}</ref> The use of entity schemas in Wikidata helps address data inconsistencies and unchecked vandalism.<ref name=":0" />

In January 2019, development started of a new extension for MediaWiki to enable storing ShEx in a separate namespace.<ref>{{cite web |url=https://www.mediawiki.org/wiki/Extension:EntitySchema |access-date=10 September 2021 |website=mediawiki.org |title=Extension:EntitySchema – MediaWiki |archive-date=25 June 2021 |archive-url=https://web.archive.org/web/20210625050439/https://www.mediawiki.org/wiki/Extension:EntitySchema |url-status=live }}</ref><ref>{{cite web|url=https://gerrit.wikimedia.org/r/plugins/gitiles/mediawiki/extensions/EntitySchema/+/26654db17345beefbd5518af48ed1bcd17288bc9|title=Initial empty repository|website=Gerrit|date=15 January 2019|access-date=12 June 2022|archive-date=19 March 2022|archive-url=https://web.archive.org/web/20220319091240/https://gerrit.wikimedia.org/r/plugins/gitiles/mediawiki/extensions/EntitySchema/+/26654db17345beefbd5518af48ed1bcd17288bc9|url-status=live}}</ref> Entity schemas are stored with different identifiers than those used for items, properties, and lexemes. Entity schemas are stored with an "E" identifier, such as [[wikidata:EntitySchema:E10|E10]] for the entity schema of human data instances and [[wikidata:EntitySchema:E270|E270]] for the entity schema of building data instances. This extension has since been installed on Wikidata<ref>{{cite web |url=https://www.wikidata.org/wiki/Special:Version |access-date=10 September 2021 |website=Wikidata.org |title=Version – Wikidata |archive-date=19 October 2021 |archive-url=https://web.archive.org/web/20211019080834/https://www.wikidata.org/wiki/Special:Version |url-status=live }}</ref> and enables contributors to use ShEx for validating and describing Resource Description Framework data in items and lexemes. Any item or lexeme on Wikidata can be validated against an entity schema,{{Clarify|date=March 2024|reason=What is an Entity Schema?}} and this makes it an important tool for quality assurance.

==Content==
[[File:Wikidata content 2024.svg|thumb|right|300px|Items for scholarly articles are the biggest part of Wikidata, followed by the collection of biographies.]]
Wikidata's content collections include data for biographies,<ref>{{Cite journal |last1=Chisholm |first1=Andrew |last2=Radford |first2=Will |last3=Hachey |first3=Ben |date=April 2017 |editor-last=Lapata |editor-first=Mirella |editor2-last=Blunsom |editor2-first=Phil |editor3-last=Koller |editor3-first=Alexander |title=Learning to generate one-sentence biographies from Wikidata |url=https://aclanthology.org/E17-1060/ |journal=Proceedings of the 15th Conference of the European Chapter of the Association for Computational Linguistics: Volume 1, Long Papers |location=Valencia, Spain |publisher=Association for Computational Linguistics |pages=633–642|arxiv=1702.06235 }}</ref> medicine,<ref>{{cite journal |last1=Turki |first1=Houcemeddine |last2=Shafee |first2=Thomas |last3=Hadj Taieb |first3=Mohamed Ali |last4=Ben Aouicha |first4=Mohamed |last5=Vrandečić |first5=Denny |last6=Das |first6=Diptanshu |last7=Hamdi |first7=Helmi |title=Wikidata: A large-scale collaborative ontological medical database |journal=Journal of Biomedical Informatics |date=November 2019 |volume=99 |article-number=103292 |doi=10.1016/j.jbi.2019.103292|pmid

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