<https://rafu.com/2013/04/%e6%97%a5%e5%b8%b8%e3%81%ae%e4%b8%ad%e3%81%ab%e6%bd%9c%e3%82%80%e9%81%8e%e5%89%b0%e6%91%82%e5%8f%96/#article>
<http://www.w3.org/1999/02/22-rdf-syntax-ns#type>
<https://rafu.com/2013/04/%E6%97%A5%E5%B8%B8%E3%81%AE%E4%B8%AD%E3%81%AB%E6%BD%9C%E3%82%80%E9%81%8E%E5%89%B0%E6%91%82%E5%8F%96/>