Re: URI-protocol mapping (was Re: How to add new "protocols" ?)

touch@isi.edu
Thu, 20 Feb 1997 11:04:39 -0800


From: touch@isi.edu
Date: Thu, 20 Feb 1997 11:04:39 -0800
Message-Id: <199702201904.AA04605@ash.isi.edu>
To: touch@isi.edu, liberte@ncsa.uiuc.edu
Subject: Re: URI-protocol mapping (was Re: How to add new "protocols" ?)
Cc: uri@bunyip.com

>  > I've been using URL as the last step in that chain.
> 
> So for you a URN necessarily maps to a URL or perhaps another URN or a
> description of the resource, but never to the resource itself.  I
> don't think that restriction is necessary.

At some point you must know
	who you're talking with
	what protocol to use

If you return that in a record from a URN server, that's 
OK too, but that's what I've been calling a URL. A URL is
a context-independent absolute identifier.

> Indirection is necessary to get the mobility that names allow, but
> indirection is possible also for URLs.  A URL is symbolic too.

We just disagree on this. I consider a URL a collapsed version
of a URN-DNS response. Everything else is a URN to me.

The value in stating it this way is that, in the end, you
must know the two things above. 

> Certainly one must eventually get down to lower level primitives.
> But both URNs and URLs can do that, unless you restrict that URNs
> can not do that.

That's what I've been doing - the point is that, at some level, you
need the lowest level primitives. What do you call them, if not URLs?

Joe
----------------------------------------------------------------------
Joe Touch - touch@isi.edu		    http://www.isi.edu/~touch/
ISI / Project Leader, ATOMIC-2, LSAM       http://www.isi.edu/atomic2/
USC / Research Assistant Prof.                http://www.isi.edu/lsam/