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URNs for 'naming authority assignment', not 'permanent'

From: Larry Masinter <LMM@acm.org>
Date: Tue, 16 Sep 2003 11:25:01 -0700
To: "'Williams, Stuart'" <skw@hp.com>
Cc: uri@w3.org, urn-nid@lists.verisignlabs.com, leslie@thinkingcat.com, thiemann@acm.org
Message-id: <002001c37c7f$d7c15b90$6a552099@MasinterT40>

(giving the thread a subject line)

> I like the idea of a univerally applied principle such as you 
> suggest. Could you expand a little on "'naming authority assignment' 
> schemes". I think I know what you are getting at... but I'm trying to
see why, 
> for example, the http URI scheme wouldn't fall on the URN namespace
side of 
> this distinction - it establishes URI assignment authorities  that
then control the
> assignment of URI within some sub-space. Maybe URI assignment
> don't fall within the locus of what you mean by a 'naming authority'.

URIs are protocol elements intended for communication.
To be useful, the definition of the URI scheme should
tell the receiver of a URI what resource the URI identifies.

When you define a URI scheme, you are expected to define the
access semantics of the scheme -- how it is that a receiver
of a URI in the scheme is supposed determine the resource
that the URI identifies. For 'http', the definition URIs with
the http scheme is in the HTTP protocol specification, and
the definition is tied to the HTTP protocol.  (People might
use HTTP URIs in other ways to indicate something else, but
that use isn't part of the definition of the HTTP scheme.)

The "urn" namespace was defined as a system which had no
defined operational interpretation for determining the
resource identified; rather, it allowed namespace authorities
to create naming rules, and that the receiver of a URN
would have to use other means to actually locate the

Of course, it is possible to treat a locator (such as a HTTP
URI) as if it were a uninterpreted identifier; many applications
of URIs do this. And it is possible to devise an operational
protocol for resolution of URNs. But neither of these are

The guidelines for IETF registration of URI schemes vs.
URN namespaces could be specific that the namespace definition
needs to be explicit about whether the operational protocol
is definitional or merely a heuristic.

For doi, hdl and info, it seems that the intent is
to make the registry itself definitional, and the resolution
mechanisms heuristic. Because of this, I think they fit
into the "URN namespace" scope.  For "tag", again, the
goal is to avoid any definition of any operational means
of identification, so it would fit into a URN namespace

However, for "tdb" and "duri" (http://larry.masinter.net/duri.html),
as well as "hash", (draft-thiemann-hash-urn-00), there *is*
an operational definition for determining the resource identified,
so they would fit better as new URI schemes.

What do you think of this as a guideline? I believe there
are many namespace registrations that are hanging because
of the weak guidelines between "URN namespace vs. URI scheme",
and this might help. Except for inertia of work already
underway, are these workable as guidelines?

Received on Tuesday, 16 September 2003 14:25:19 UTC

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