<https://lyes.tw/blog/post/33586318-%e5%8d%97%e7%be%8e%e6%98%a5%e5%ae%a4the-pool>
<http://www.w3.org/1999/02/22-rdf-syntax-ns#type>
<https://lyes.tw/blog/post/33586318-%E5%8D%97%E7%BE%8E%E6%98%A5%E5%AE%A4the-pool>