Danish Agency for Libraries and Media is Registration Authority for ISO 15511 Information and documentation - International Standard Identifier for Libraries and Related Organizations (ISIL).
I think it's worth exploring with some care what URIs were meant to be, and how they are being used in practice. In particular, I want to look at what illumination might be contributed from our understanding of how other kinds of identifiers work.
The International Standard Text Code (ISTC) is a new identifier for the book industry. Whereas International Standard Book Numbers (ISBNs) provide a unique identity in the supply chain for each individual product format (either physical products—hardback, paperback; or digital products and formats—downloadable audiobook, PDF e-book, etc.), an ISTC identifies the underlying creative textual work.