DPK argues that the thing that made the early web "click", the thing that allowed it to "break out" in the 1990s, was not HTML, not HTTP, but the standardization on URIs as "addresses".
So, it must be the URI. Yes: The URI, initially "UDI" (Universal *Document* Identifier, not "Resource" identifier), or more specifically the URL, is a brief, declarative, machine-followable, secure instruction, telling you where in the vast existing maze of the Internet one might find a file to download, and more specifically *how* to find it.
I agree.