Wikidata is a collaboratively edited knowledge base operated by the Wikimedia Foundation. It is intended to provide a common source of data which can be used by Wikimedia projects such as Wikipedia, and by anyone else, under a public domain licence. 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.
Wikidata is a document-oriented database, focused on items. Each item represents a topic (or an administrative page used to maintain Wikipedia) and is identified by a unique number, prefixed with the letter Q—for example, the item for the topic Politics is Q7163. This enables the basic information required to identify the topic the item covers to be translated without favouring any language.
Information is added to items by creating statements. Statements take the form of key-value pairs, with each statement consisting of a property (the key) and a value linked to the property.
The creation of the project was funded by donations from the Allen Institute for Artificial Intelligence, the Gordon and Betty Moore Foundation, and Google, Inc., totaling €1.3 million. Initial development of the project is being overseen by Wikimedia Deutschland and has been split into three phases:
- 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
Wikidata was launched on 30 October 2012 and was the first new project of the Wikimedia Foundation since 2006. At this time, only the first phase 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.
Historically, a Wikipedia article would include a list of interlanguage links, being links to articles on the same topic in other editions of Wikipedia, if present. Initially, Wikidata was a self-contained repository of interlanguage links. No Wikipedia language editions were 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 Hebrew and 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, the power to delete them from the English Wikipedia was granted to automatic editors (bots). On 23 September 2013, phase 1 went live on Wikimedia Commons. 
The first aspects of the second phase were deployed on 4 February 2013, introducing statements to Wikidata entries. The values 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.
On 16 September 2015, Wikidata began allowing so-called arbitrary access, or access to properties of Wikidata items which were not directly connected to it. For example, in the past the article about Berlin you could not access data about Germany, but with arbitrary access it could. On 27 April 2016 arbitrary access was activated on Wikimedia Commons.
Phase 3 will involve database querying and the creation of lists based on data stored on Wikidata. As of October 2016 two tools for querying Wikidata (Wikidata:List of queries) were available: AutoList and PetScan, additionally to a public SPARQL endpoint .
- ↑ 1.0 1.1 Wikidata (Template:Webarchive)
- ↑ "Data Revolution for Wikipedia". Wikimedia Deutschland. March 30, 2012. Archived from the original on September 11, 2012. http://www.wikimedia.de/wiki/Pressemitteilungen/PM_3_12_Wikidata_EN. Retrieved September 11, 2012.
- ↑ Wikibase
- ↑ Dickinson, Boonsri (March 30, 2012). "Paul Allen Invests In A Massive Project To Make Wikipedia Better". Business Insider. Retrieved September 11, 2012.
- ↑ Perez, Sarah (March 30, 2012). "Wikipedia’s Next Big Thing: Wikidata, A Machine-Readable, User-Editable Database Funded By Google, Paul Allen And Others". TechCrunch. Archived from the original on September 11, 2012. Retrieved September 11, 2012.
- ↑ 6.0 6.1 https://meta.wikimedia.org/wiki/Wikidata
- ↑ Template:Cite mailing list
- ↑ Roth, Matthew (March 30, 2012). "The Wikipedia data revolution". Wikimedia Foundation. Archived from the original on September 11, 2012. Retrieved September 11, 2012.
- ↑ Pintscher, Lydia (14 January 2013). "First steps of Wikidata in the Hungarian Wikipedia". Wikimedia Deutschland. http://blog.wikimedia.de/2013/01/14/first-steps-of-wikidata-in-the-hungarian-wikipedia/. Retrieved 17 December 2015.
- ↑ Pintscher, Lydia. "Wikidata coming to the next two Wikipedias". Wikimedia Deutschland. http://blog.wikimedia.de/2013/01/30/wikidata-coming-to-the-next-two-wikipedias/. Retrieved January 31, 2013.
- ↑ Pintscher, Lydia (13 February 2013). "Wikidata live on the English Wikipedia". Wikimedia Deutschland. http://blog.wikimedia.de/2013/02/13/wikidata-live-on-the-english-wikipedia/. Retrieved 15 February 2013.
- ↑ Pintscher, Lydia (6 March 2013). "Wikidata now live on all Wikipedias". Wikimedia Deutschland. http://blog.wikimedia.de/2013/03/06/wikidata-now-live-on-all-wikipedias/. Retrieved 8 March 2013.
- ↑ "Wikidata ist für alle Wikipedien da"German. Golem.de. Retrieved 29 January 2014.
- ↑ "Wikipedia talk:Wikidata interwiki RFC". March 29, 2013. http://en.wikipedia.org/w/index.php?title=Wikipedia_talk:Wikidata_interwiki_RFC&oldid=547663432. Retrieved March 30, 2013.
- ↑ Lydia, Pintscher (23 September 2013). "Wikidata is Here!". Commons:Village pump.
- ↑ Pintscher, Lydia. "Wikidata/Status updates/2013 03 01". Wikimedia Meta-Wiki. Wikimedia Foundation. http://meta.wikimedia.org/wiki/Wikidata/Status_updates/2013_03_01. Retrieved 3 March 2013.
- ↑ Pintscher, Lydia (27 March 2013). "You can have all the data!". Wikimedia Deutschland. http://blog.wikimedia.de/2013/03/27/you-can-have-all-the-data/. Retrieved 28 March 2013.
- ↑ "Wikidata goes live worldwide". The H. 2013-04-25. Archived from the original on 3 January 2014.
- ↑ Lydia, Pintscher (16 September 2015). "Wikidata: Access to data from arbitrary items is here". Wikipedia:Village pump (technical). Retrieved 30 August 2016.
- ↑ Lydia, Pintscher (27 April 2016). "Wikidata support: arbitrary access is here". Commons:Village pump. Retrieved 30 August 2016.
- ↑ 21.0 21.1 21.2 Kolbe, Andrew (December 8, 2015). "Unsourced, unreliable, and in your face forever: Wikidata, the future of online nonsense". The Register.
- ↑ commons:File talk:Wikidata-logo-en.svg#Hybrid. Retrieved 2016-10-06.
- Denny Vrandečić, Markus Krötzsch: Wikidata: A Free Collaborative Knowledge Base. Communications of the ACM. ACM. 2014 (preprint).
- Claudia Müller-Birn, Benjamin Karran, Janette Lehmann, Markus Luczak-Rösch: Peer-production system or collaborative ontology development effort: What is Wikidata? In, OpenSym 2015 - Conference on Open Collaboration, San Francisco, US, 19 - 21 Aug 2015 (preprint).
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