[Wikidata] Metadata about Persistent Identifiers

At PIDapalooza 2018 https://pidapalooza.org/ I discussed with a few people - not Wikidatans - how to document Persistent (or Unique) Identifiers. As an example, I created 'KoreaMed Unique Identifier': https://www.wikidata.org/wiki/Q47489994 How could we improve that? What additional properties might we need? What properties already exist, that we could make use of? Also, this query: http://tinyurl.com/y6wdrbhd returns over 5000 instances/ subclasses of "unique identifier" (Q6545185) but includes both /types/ of identifiers (like the example above) and individual identifier values, like ".ar" as an internet TLD (domain name itself - Q32635 - is a subclass, not an instance, of UID) - how should we distinguish between the two classes? -- Andy Mabbett @pigsonthewing http://pigsonthewing.org.uk