<https://blog.dynanmemo.com/archives/tag/%e3%82%b3%e3%83%91%e3%83%bb%e3%82%b9%e3%83%80%e3%83%a1%e3%83%aa%e3%82%ab%e3%83%bc%e3%83%8a>
<http://www.w3.org/1999/02/22-rdf-syntax-ns#type>
<https://blog.dynanmemo.com/archives/tag/%E3%82%B3%E3%83%91%E3%83%BB%E3%82%B9%E3%83%80%E3%83%A1%E3%83%AA%E3%82%AB%E3%83%BC%E3%83%8A>