<https://sushi-naniwa.info/2015/03/14/%e6%9c%a8%e7%93%9c%e3%81%ae%e8%8a%b1/#article>
<http://www.w3.org/1999/02/22-rdf-syntax-ns#type>
<https://sushi-naniwa.info/2015/03/14/%E6%9C%A8%E7%93%9C%E3%81%AE%E8%8A%B1/>