<https://kariyasui.com/%e4%bf%9d%e9%99%ba%e4%bb%a3%e7%90%86%e6%a5%ad/post-275/>
<http://www.w3.org/1999/02/22-rdf-syntax-ns#type>
<https://kariyasui.com/%E4%BF%9D%E9%99%BA%E4%BB%A3%E7%90%86%E6%A5%AD/post-275/>