<https://mutsumi-kai.com/2020/07/25/%e5%89%8d%e3%82%92%e5%90%91%e3%81%8f%e3%81%a8%e3%81%84%e3%81%86%e3%81%9d%e3%82%8c%e3%81%a0%e3%81%91%e3%81%a7/#article>
<http://www.w3.org/1999/02/22-rdf-syntax-ns#type>
<https://mutsumi-kai.com/2020/07/25/%E5%89%8D%E3%82%92%E5%90%91%E3%81%8F%E3%81%A8%E3%81%84%E3%81%86%E3%81%9D%E3%82%8C%E3%81%A0%E3%81%91%E3%81%A7/>