To the exact questions you asked, the answer is mu because of <https://www.w3.org/TR/uri-clarification/ https://www.w3.org/TR/uri-clarification/>. Correcting f

To the exact questions you asked, the answer is mu because of <https://www.w3.org/TR/uri-clarification/ https://www.w3.org/TR/uri-clarification/>. Correcting for the intention: yes, books are easy to identify! <https://www.iana.org/assignments/urn-formal/isbn https://www.iana.org/assignments/urn-formal/isbn> You also want to able to dereference. I edited my DOM copy of your comment to add the hyperlink <a href="urn:isbn:9780062515872"> to the book's name, then clicked it. Firefox prompted me to pick a local executable. ISTR Netscape used to handle this a bit more gracefully. It is perfectly okay that not every UA implements every conceivable scheme, the particularities of the failure do not diminish the idea of the Web. I happen to know archivists and librarians. They use specialised information systems that are not part of the Web. There does not seem to be an urgent need to uplift the legacy. IMO the grade is not "no", but "the foundations are there ready to be built upon".