<https://www.hps-pigging.com/heres-why-you-should-use-hps-for-your-pigging-project/#article>
<http://www.w3.org/1999/02/22-rdf-syntax-ns#type>
<https://www.hps-pigging.com/heres-why-you-should-use-hps-for-your-pigging-project/>