While URIs are the foundational building block of identification on the Web, the “URN URI namespace” has its own recognition, and is managed through IANA as well. Technically, it’s “just a URI scheme”, but logically, it is one that is more openly managed than most others. For this reason, it makes sense to add URN Namespaces as a new concept to
The initial list of namespaces is very short, and it will be interesting to see how many of the IANA-registered namespaces are still popular enough to get added to this list over time. As usual, feel free to add via PR (preferred), or simply raise an issue if you would like to see a URN namespace added.