A semantic wiki is a wiki that stores some portion of its data in a way that can be queried elsewhere. Typical uses of such data include querying it within the wiki (sometimes using standard query languages like SPARQL), aggregating it in displays like tables, maps and calendars; exporting it via formats like RDF, OWL or CSV; and reasoning with it, to calculate new facts from the given facts. Semantic wikis do not necessarily need to include standards or technologies considered part of the Semantic Web, although they usually do, to some extent.
Semantic wikis can use either pre-defined ontologies, or their own, self-contained "folksonomies".
Semantic wiki engines
Many semantic wiki engines were proposed and developed in the mid-2000s, especially by academic research groups, but the number of engines that are still under active development and usage has trailed off significantly since then. See the page semantic wiki projects for a full listing of wiki engines listed on this site, and the status of each.