__Wikidata__ is a Wiki knowledge base hosted by the Wikimedia Foundation. It is a common source of open data that Wikimedia projects such as Wikipedia can use, and by anyone else, under a public domain license.
This is similar to the way Wikimedia Commons provides storage for media files and access to those files for all Wikimedia projects, and which are also freely available for reuse. Wikidata is powered by the software Wikibase - wikipedia
# Strategic importance
Some comments I agree with:
One thing the document concerns itself with at least as much as with Wikipedia is “data structures”—and this nods to Wikidata, which has been the new hotness for awhile, but whose centrality to the larger project is becoming clearer all the time - thewikipedian.net
Take just one easily overlooked line, about how most Wikimedia content is “long-text, unstructured articles”. You know, those lo-fi Wikipedia entries that remain so enduringly popular. They lack structure now, but they might not always. Imagine a future where Wikidata provides information not just to infoboxes (although that is a tricky subject) but also to boring old Wikipedia itself.
Forget “red links”: every plain text noun in the whole project may be connected to its “Q number”. Using AI and machine learning, entire concepts can be quickly linked in a way that once required many lifetimes.
At present, Wikipedia is the closest thing we have to the “sum of all human knowledge” but in the future, it may only be the default user interface. Now more than ever, the real action is happening behind the scenes.
Wikidata is a document-oriented database, focused on ''items''. Each item represents a topic and is identified by a unique number, prefixed with the letter Q — for example, the item for the topic is :d:Q42 — known as a "__QID__". This enables the basic information required to identify the topic the item covers to be translated without favouring any language - wikipedia
An ''item'' can have one or more statements. Information is added to items by creating statements, in the form of key-value pairs, with each statement consisting of a ''property'' (the key) and a value linked to the property.
Additionally, a qualifier can refine the meaning of the statement by providing additional information that applies to the scope of the statement. References can be provided per statement - wikipedia
A ''property'' describes the data value of a statement and can be thought of as a category of data, for example "color" for the data value "blue." Properties, when paired with values, form a statement in Wikidata.
Properties are also used in qualifiers. Properties have their own pages on Wikidata and are connected to items, resulting in a linked data structure, where the property represents a triplet's predicate.
Property pages also contain ''constraints'', which are rules about how a particular property should be used. For instance most identifiers should have only one value, so there is a ''single value constraint'' on them - wikipedia
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 of storing the language to which the lexeme refers, they have a section for ''forms'' and a section for ''senses''.
# See also