<https://kishida-seiwado.com/blog/%e6%89%8b%e6%9b%b8%e3%81%8d%e5%8d%b0%e5%88%b7%e3%81%ae%e6%84%8f%e5%a4%96%e3%81%aa%e5%8a%b9%e6%9e%9c/#article>
<http://www.w3.org/1999/02/22-rdf-syntax-ns#type>
<https://kishida-seiwado.com/blog/%E6%89%8B%E6%9B%B8%E3%81%8D%E5%8D%B0%E5%88%B7%E3%81%AE%E6%84%8F%E5%A4%96%E3%81%AA%E5%8A%B9%E6%9E%9C/>