the 1980s, before the Web began, there were several technologies to process typed links between collectively maintained hypertext pages, such as NoteCards, KMS, and gIBIS. Extensive research was published on these tools by the collaboration software, computer-mediated communication, hypertext, and computer supported cooperative work communities. The first known usage of the term "Semantic Wiki" was a Usenet posting by Andy Dingley in January 2001. Its first known appearance in a technical paper was in a 2003 paper by Austrian researcher Leo Sauermann. Many of the existing semantic wiki applications were started in the mid-2000s, including ArtificialMemory (2004), Semantic MediaWiki (2005), Freebase (2005), and OntoWiki (2006). June 2006 saw the first meeting dedicated to semantic wikis, the "SemWiki" workshop, co-located with the European Semantic Web Conference in Montenegro. This workshop ran annually until 2010. The site DBpedia, launched in 2007, though not a semantic wiki, publishes structured data from Wikipedia in RDF form, which enables semantic querying of Wikipedia's data. In March 2008, Wikia, the world's largest wiki farm, made the use of Semantic MediaWiki available for all their wikis on request, thus allowing all the wikis they hosted to function as semantic wikis. However, since upgrading to version 1.19 of MediaWiki in 2013, they have stopped supporting Semantic MediaWiki for new requests on the basis of performance problem. In July 2010, Google purchased Metaweb, the company behind Freebase. In April 2012, work began on Wikidata, a collaborative, multi-language store of data, whose data could then be used within Wikipedia articles, as well as by the outside world. Semantic wiki software There are a number of wiki applications that provide semantic functionality. Some standalone semantic wiki applications exist, including OntoWiki. Other semantic wiki software is structured as extensions or plugins to standard wiki software. The best-known of these is Semantic MediaWiki, an extension to MediaWiki. Another example is the SemanticXWiki extension for XWiki. Some standard wiki engines also include the ability to add typed, semantic links to pages, including PhpWiki and Tiki Wiki CMS Groupware. Freebase, though not billed as a wiki engine, is a web database with semantic-wiki-like properties. Common features Semantic wikis vary in their degree of formalization. Semantics may be either included in, or placed separately from, the wiki markup. Users may be supported when adding this content, using forms or autocompletion, or more complex proposal generation or consistency checks. The representation language may be wiki syntax, a