<https://www.mount-bird.jp/topics/%e8%ac%b9%e8%b3%80%e6%96%b0%e5%b9%b4%ef%bc%88%e3%82%8f%e3%81%8b%e3%81%b0%e3%81%ae%e5%ae%b6%ef%bc%89/>
<http://www.w3.org/1999/02/22-rdf-syntax-ns#type>
<https://www.mount-bird.jp/topics/%E8%AC%B9%E8%B3%80%E6%96%B0%E5%B9%B4%EF%BC%88%E3%82%8F%E3%81%8B%E3%81%B0%E3%81%AE%E5%AE%B6%EF%BC%89/>