<https://blog.eotona.com/%e3%82%b5%e3%82%ae%e3%81%ae%e3%83%90%e3%83%88%e3%83%ab/>
<http://www.w3.org/1999/02/22-rdf-syntax-ns#type>
<https://blog.eotona.com/%E3%82%B5%E3%82%AE%E3%81%AE%E3%83%90%E3%83%88%E3%83%AB/>