<http://midori-fu.com/>
<http://www.w3.org/1999/02/22-rdf-syntax-ns#type>
<http://midori-fu.com/blog/%E2%99%AA%E7%B4%B9%E4%BB%8B%E2%91%AD-%E8%AE%83%E5%B2%90%E3%81%86%E3%81%A9%E3%82%93-%E5%B9%85%E5%B1%8B%E2%99%AA/>