The [[wp:DBpedia]] project aims to interconnect the world's open data sets. (There are other similar projects like [[wp:Freebase]].)
<blockquote>DBpedia is a crowd-sourced community effort to extract structured information from Wikipedia and make this information available on the Web. DBpedia allows you to ask sophisticated queries against Wikipedia, and to link the different data sets on the Web to Wikipedia data. We hope that this work will make it easier for the huge amount of information in Wikipedia to be used in some new interesting ways. Furthermore, it might inspire new mechanisms for navigating, linking, and improving the encyclopedia itself.</blockquote>
One main dataset they "translate" into RDF is the Wikipedia data. Although the freeform content of Wikipedia is not data, the extensive use of 'infoboxes' does give structure to the content (and visual styling too). Then this content ''can'' be mapped into actual ontologies (if they aren't already semantically mapped in Wikipedia itself <ref>[https://www.mediawiki.org/wiki/Extension:Page_Forms Page Forms] are often used to make it easy for users to enter the data, which is mapped into a semantic template.</ref>.)
[[Category:Semantic]]
[[Category:Data]]
[[Category:Wiki]]