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Wikidata
Main page of Wikidata in April 2021
Type	Template:Hlist

Wikidata is a collaboratively edited multilingual knowledge graph hosted by the Wikimedia Foundation. It is a common source of open data that Wikimedia projects such as Wikipedia, 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 triples).

Concept

Template:Center

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"Template:Efn. 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 Template:Wikidata entity link, Template:Wikidata entity link, Template:Wikidata entity link, Template:Wikidata entity link, and Template:Wikidata entity link.

Item labels do not need to be unique. For example, there are two items named "Elvis Presley": Template:Wikidata entity link, which represents the American singer and actor, and Template:Wikidata entity link, which represents his 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

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

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 Template:Wikidata entity link with the value Template:Wikidata entity link under the item Template:Wikidata entity link.

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 Template:Wikidata entity link 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.

Properties

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 Template:Wikidata entity link.

Properties may also define more complex rules about their intended usage, termed constraints. For example, the Template:Wikidata entity link 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.

The most used property is Template:Wikidata entity link, which is used on more than 290,000,000 item pages Template:As of

Lexemes

Wikidata Klingon lexeme entry

In linguistics, a lexeme is a unit of lexical meaning representing a group of words that share the same core meaning and grammatical characteristics. Similarly, Wikidata's lexemes are items with a structure that makes them more suitable to store lexicographical data. Since 2016, Wikidata has supported lexicographical entries in the form of lexemes.

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 book and cow. Lexicographical entries in Wikidata can contain statements, senses, and forms. 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, with a total of 101,137 lexemes, followed by English with 38,122 lexemes. There are over 668 languages with lexicographical entries on Wikidata.

Entity schemas

Human entity schema in Wikidata

In Wikidata, a schema is a data model that outlines the necessary attributes for a data item. For instance, a data item that uses the attribute "instance of" with the value "human" would typically include attributes such as "place of birth," "date of birth," "date of death," and "place of death." The entity schema in Wikidata utilizes Shape Expression (ShEx) to describe the data in Wikidata items in the form of a Resource Description Framework (RDF). The use of entity schemas in Wikidata helps address data inconsistencies and unchecked vandalism.

In January 2019, development started of a new extension for MediaWiki to enable storing ShEx in a separate namespace. 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 E10 for the entity schema of human data instances and E270 for the entity schema of building data instances. This extension has since been installed on Wikidata 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,Template:Clarify and this makes it an important tool for quality assurance.

Content

Items for scholarly articles are the biggest part of Wikidata, followed by the collection of biographies.

Wikidata's content collections include data for biographies, 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