Question and answer based search engine using DBpedia?
Automated natural language question answering systems are different from “search engines”. For me, “semantic” generally refers to the W3C specified “semantic web” technologies, which include DBpedia. Natural language, or “conversational”, *dialog systems* may or may not be “question answering systems” and may or may not be “semantic” per se.
As far as I know, there is currently no general purpose dialog system available based primarily on conventional “semantic web” technologies; however, I believe that Paul Allen‘s “Digital Aristotle” Project Halo [1] is or was heavily based on DBpedia. See my quick and dirty literature review on “DBpedia & Natural Language Agents 2011” [2].
[1] projecthalo.com
[2] meta-guide.com/home/bibliography/google-scholar/dbpedia-natural-language-agents