But it's not the only scenario I would consider. If we're going to be stuck with multiple registries, it's important that we be able to register services for any URN in any registry. I would refine this further so that the naming authority can register any subset of its URN space to a set of resolution services for that subset. It's false only if everyone runs a proxy. Perhaps if we accept the idea that clients can do anything they want, then we don't need to talk about the special cases.
Caching proxies are essential for the scalability of the web.
To me, the latter looks more promising. Hmm, we're talking about different things. The second stage is directed by the info found from the first stage. I see no need to have a common prefix for all names. We can't require any such thing, anyway, and we'd be arrogant to try.