Tagging makes information searchable by humans. The semantic web, on the other hand, is searchable by computers via the Resource Description Framework (RDF) being integrated into webpages. Most Web 2.0 tools, such as Wikis, do not have such a framework but depend on human tagging.
There is wiki software that has integrated both – the Semantic MediaWiki. This framework enables computers to process the knowledge created and stored in a Semantic MediaWiki. It does this by introducing additional markup to the text. It is then stored in proper RDF format – so that if a semantic web application were to search it, it would be able to find the desired information. The wiki becomes a data source for semantic web applications.