Wikidata

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:

• Obligatorily, an identifier (the QID), related to a label and a description.
• Optionally, multiple aliases and some number of statements (and their properties and values).

Three statements from 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 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 milk (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.[5]

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".[6]

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 "as of 2011". Values in the statements may also be annotated with references, pointing to a source backing up the statement's content.[7] As with statements, all qualifiers and references are property–value pairs.

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 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.[8]

Before a new property is created, it needs to undergo a discussion process.[9][10]

The most used property is cites work (P2860), which is used on more than 280,000,000 item pages as of October 2022.[11]

In linguistics, a 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.[12]

In January 2019 development started of a new extension for MediaWiki to enable storing Shape Expressions in a separate namespace.[13][14]

This extension has since been installed on Wikidata[15] 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.

A Wikipedia article's list of interlanguage links as they appeared in an edit box (left) and on the article's page (right) prior to Wikidata. Each link in these lists is to an article that requires its own list of interlanguage links to the other articles; this is the information centralized by Wikidata.

The "Edit links" link nowadays takes the reader to Wikidata to edit interlanguage and interwiki links.

Wikidata was launched on 29 October 2012 and was the first new project of the Wikimedia Foundation since 2006.[3][19][20] 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.[21] 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.[22] This functionality was extended to the Hebrew and Italian Wikipedias on 30 January, to the English Wikipedia on 13 February and to all other Wikipedias on 6 March.[23][24][25][26] After no consensus was reached over a proposal to restrict the removal of language links from the English Wikipedia,[27] they were automatically removed by bots. On 23 September 2013, interlanguage links went live on Wikimedia Commons.[28]

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.[29]

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.[30][31] 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.[32] On 27 April 2016 arbitrary access was activated on Wikimedia Commons.[33]

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 data silos.[34]

On 7 September 2015, the Wikimedia Foundation announced the release of the Wikidata Query Service,[35] which lets users run queries on the data contained in Wikidata.[36] The service uses SPARQL as the query language. As of November 2018, there are at least 26 different tools that allow querying the data in different ways.[37] It uses Blazegraph as its triplestore and graph database.[38][39]

The bars on the logo contain the word "WIKI" encoded in Morse code.[40] It was created by Arun Ganesh and selected through community decision.[41]