# Re: Suggest meaning for URN

Peter Deutsch (peterd@bunyip.com)
Tue, 8 Jun 1993 12:42:32 -0400

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    Message-Id: <9306081642.AA01746@expresso.bunyip.com>

    From: Peter Deutsch <peterd@bunyip.com>

    Date: Tue, 8 Jun 1993 12:42:32 -0400

    In-Reply-To: Tim Berners-Lee's message as of Jun  7, 14:47

    To: timbl@nxoc01.cern.ch

    Subject: Re: Suggest meaning for URN

Hi Tim,

Come on, play fair!

[ You wrote: ]
. . .
> Ed, you say "symbolic reference". A "reference" can normally be
> dereferenced. If it can't, then fair enough but say that it
> supports equality but that's it.
>
> If it can, then you have to have an algorithm in mind, which will
> almost certainly involved the user knowing a little about the inside
> of a URN, to know the first step to dereferencing it.

Actually, I think the user need know very little about the
structure of a URN to use it, any more than most people
know much about the working of an internal combustion
engine to drive their car, or DNS to find an IP address
(sure, it's nice to know that `.ch' is Switzerland, but
nobody _needs_ to know this to use DNS).

Of course, our software needs to be able to find
appropriate servers, ask appropriate questions and
understand the responses but I think we are vastly
overrating the difficulty of this. After all, Users of DNS
have been doing this successfully for some time now and
nobody looks all that surprised. Imagine if everyone had
said "but you can't use a lookup service for IP addresses!
It wont scale to googleplex hostnames!".

Fact is, a single server (replicated for performance and
redundancy) can handle several million records today. As
the quantity of URNs to be served passes this magic
number, we can add independent servers for each namespace.
(ie. a set of servers for ISOC, a set for ISBN and so on).

> Th eonly proposals I have heard of which doesn't need this structure
> are Peter's, whereby however many documents everyone can write, he
> can still buy a bigger disk to index them ;-), and a suggestion of
> Robert Acskyn that one could have a large distributed and replicated
> set of servers into which one would hash the URN. The last is the
> only attempt I have heard of to scale up the dereferencing of opaque
> names.

Actually, I don't think I every advocated a single server
for the entire world to the end of time. I have argued
that indexing a couple of million anythings is just not
the hard problem people seem to think it is, but that's
not the same at all.

Let's face it, DNS is currently tracking something like
two million host names. Both archie and veronica are
serving over two million filenames and so on. And when the
numbers require it for individual namespaces, we can start
distributing the contents a la DNS. There's nothing in our
current proposal that rules that out.

> So, Ed, can you dereference a URN?

Sure, why not? And as we end up with more and more people
creating and serving URNs, we will see distributed
solutions, probably marrying DNS (to find the appropriate
server) and a simple table lookup protocol (to hand in a
URN and get back zero or more URLs). This is simply not
brain surgery. Or if it is, then we're all brain surgeons.

- peterd

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