<https://eishinken.com/blog/4%e5%a5%b3%e3%83%80%e3%82%a6%e3%83%b3%e3%80%9c/>
<http://www.w3.org/1999/02/22-rdf-syntax-ns#type>
<https://eishinken.com/blog/4%E5%A5%B3%E3%83%80%E3%82%A6%E3%83%B3%E3%80%9C/>