To try this from a different angle…
Let’s say one wanted to capture information about an identifier itself. Not the thing the identifier identifies, but the identifier itself.
So, for example, ISSNs are issued by specific agencies. Bowker, in the example below, manages ISBNs. So, the identifiers themselves might have metadata associated with them (when they were created, who applied for it, etc). If Bowker or an ISSN agency wanted to publish linked data about the identifier, how might you go about modelling that?