Wikidata is a
document-oriented database, focused on items, which represent any kind of topic, concept, or object. Each item is allocated a unique,
persistent identifier, a positive integer prefixed with the upper-case letter Q, known as a "QID". Q is the first name of Qamarniso Vrandečić (née Ismoilova), an Uzbek Wikimedian married to the Wikidata co-developer
Denny Vrandečić. This enables the basic information required to identify the topic that the item covers to be translated without favouring any language.
identifier (the QID), related to a label and a description.
Optionally, multiple aliases and some number of statements (and their properties and values).
Statements are how any information known about an item is recorded in Wikidata. Formally, they consist of
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
color (P462) with the value
white (Q23444) under the item
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.
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
official website (P856) may only be paired with values of type "URL".
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. As with statements, all qualifiers and references are property–value pairs.
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
subproperty of (P1647).
Properties may also define more complex rules about their intended usage, termed constraints. For example, the
capital (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.
Before a new property is created, it needs to undergo a discussion process.
lexeme is a unit of
lexical meaning. Similarly, Wikidata's lexemes are items with a structure that makes them more suitable to store
lexicographical data. Besides storing the language to which the lexeme refers, they have a section for forms and a section for senses.
In January 2019, development started of a new extension for MediaWiki to enable storing
Shape Expressions in a separate namespace.
This extension has since been installed on Wikidata and enables contributors to use Shape Expressions 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, and this makes it an important tool for quality assurance.
Centralising interlanguage links – links between Wikipedia articles about the same topic in different languages.
Providing a central place for
infobox data for all Wikipedias.
Creating and updating list articles based on data in Wikidata and linking to other Wikimedia sister projects, including
Meta-Wiki and the own Wikidata (interwikilinks).
Wikidata was launched on 29 October 2012 and was the first new project of the Wikimedia Foundation since 2006. At this time, only the centralization of language links was available. This enabled items to be created and filled with basic information: a label – a name or title, aliases – alternative terms for the label, a description, and links to articles about the topic in all the various language editions of Wikipedia (interwikipedia links).
Historically, a Wikipedia article would include a list of interlanguage links (links to articles on the same topic in other editions of Wikipedia, if they existed). Wikidata was originally a self-contained
repository of interlanguage links. Wikipedia language editions were still not able to access Wikidata, so they needed to continue to maintain their own lists of interlanguage links.
On 14 January 2013, the
Hungarian Wikipedia became the first to enable the provision of interlanguage links via Wikidata. This functionality was extended to the
Italian Wikipedias on 30 January, to the
English Wikipedia on 13 February and to all other Wikipedias on 6 March. After no consensus was reached over a proposal to restrict the removal of language links from the English Wikipedia, they were automatically removed by
bots. On 23 September 2013, interlanguage links went live on Wikimedia Commons.
Statements and data access
On 4 February 2013, statements were introduced to Wikidata entries. The possible values for properties were initially limited to two data types (items and images on Wikimedia Commons), with more
data types (such as
coordinates and dates) to follow later. The first new type, string, was deployed on 6 March.
The ability for the various language editions of Wikipedia to access data from Wikidata was rolled out progressively between 27 March and 25 April 2013. On 16 September 2015, Wikidata began allowing so-called arbitrary access, or access from a given article of a Wikipedia to the statements on Wikidata items not directly connected to it. For example, it became possible to read data about Germany from the Berlin article, which was not feasible before. On 27 April 2016 arbitrary access was activated on Wikimedia Commons.
According to a 2020 study, a large proportion of the data on Wikidata consists of entries imported en masse from other databases by
Internet bots, which helps to "break down the walls" of
The bars on the
logo contain the word "WIKI" encoded in
Morse code. It was created by Arun Ganesh and selected through community decision.
In November 2014, Wikidata received the Open Data Publisher Award from the
Open Data Institute "for sheer scale, and built-in openness".
In December 2014, Google announced that it would shut down
Freebase in favor of Wikidata.
As of November 2018[update], Wikidata information was used in 58.4% of all English Wikipedia articles, mostly for external identifiers or coordinate locations. In aggregate, data from Wikidata is shown in 64% of all
Wikipedias' pages, 93% of all
Wikivoyage articles, 34% of all
Wikiquotes', 32% of all
Wikisources', and 27% of Wikimedia Commons's. Usage in other
Wikimedia Foundation projects is a testimonial.
As of December 2020[update], Wikidata's data was visualized by at least 20 other external tools and over 300 papers have been published about Wikidata.
^Samuel, John (15 August 2018). "Experimental IR Meets Multilinguality, Multimodality, and Interaction". Experimental IR Meets Multilinguality, Multimodality, and Interaction.
CLEF 2018. Lecture Notes in Computer Science. Vol. 11018. p. 129.
^Mora-Cantallops, Marçal; Sánchez-Alonso, Salvador; García-Barriocanal, Elena (2 September 2019). "A systematic literature review on Wikidata". Data Technologies and Applications. 53 (3): 250–268.