From W3C Wiki
In contrast to the World Wide Web which is a global network of file systems, the Semantic Web is a globally distributed network of databases embodied in formal logic. Accessibility allowed the World Wide Web quickly reach critical mass. Likewise, the success of the Semantic Web hinges on the average user's ability to quickly update and query Semantic Web databases. For these users, who have difficulty with simple Boolean expression, the learning curve for the logical formalisms and specifications of the Semantic Web creates the most cited barrier to adoption. In response, a growing number of systems are being proposed which allow users to harness natural (or plain) language as a tool for knowledge assertion and querying.
Ginseng allows update and query of SW databases using a restricted grammar
OWL verbalizer expresses the content of OWL ontologies in English