Public Identifiers

Steven R. Newcomb srn at
Mon Sep 21 13:38:51 BST 1998

Thanks, John Cowan, for your clear answer, but the language you cite
from RFC 1737 only re-opens the question and casts doubt on your
answer, at least in my mind.

> From: John Cowan <cowan at>
> Date: Sun, 20 Sep 1998 20:43:28 -0400 (EDT)
> Steven R. Newcomb scripsit:
> > Will URNs permit pointing to things that aren't now and may never be
> > on the web? I mean, things that their owners never intended to be on
> > the web and either that their owners do not want to appear on the web,
> > or that their owners may not (currently) see any interest in putting
> > on the web?
> Clearly yes.  RFC 1737, "Functional Requirements for Uniform Resource Names",
> says:
> # A URN identifies a resource or
> # unit of information.  It may identify, for example, intellectual
> # content, a particular presentation of intellectual content, or
> # whatever a name assignment authority determines is a distinctly
> # namable entity.  A URL identifies the location or a container for an
> # instance of a resource identified by a URN.  The resource identified
> # by a URN may reside in one or more locations at any given time, may
> # move, or may not be available at all.
> Note especially the last phrase.

The problems with the quotation from RFC 1737 are these:

* Who defines what constitutes a name assignment authority?  If it's
  the end user, in an ad hoc fashion, that's fine, I'm satisfied.  But
  the language of the RFC, 

> # For example, ISBN numbers, ISO
> # public identifiers, and UPC product codes seem to satisfy the
> # functional requirements, and allow an embedding that satisfies
> # the syntactic requirements described here.

  ...indicates otherwise.  Here, in all three examples, there is a
  name registration authority; the end user is evidently not allowed
  to specify the Sears 1922 Farm Catalog unless this has already
  become a formally-cataloged public entity of some kind.  (Note that
  it's not clear whether "ISO public identifiers" means "public
  identifiers in ISO syntax" or "public identifiers that begin with
  the letters 'ISO' and that define public text entities that were
  created under the auspices of the ISO".  There is a very small set
  of the latter -- a set that has little or nothing to do with what
  I'm concerned about here.)

* There is an even more problematic statement: "A URL identifies the
  location or a container for an instance of a resource identified by
  a URN."  This strongly implies that there must be a URL behind every
  URN, even if that URL is fictitious or doesn't happen to work.  It
  also implies that there is some sort of locatable online container.

> These rules are documented in RFC2141, "URN Syntax".

The fact that you make such a point of demonstrating the conversion of
my FPI into a URN makes me wonder whether you understood my question.
In the scenario I'm asking about, there is never any need to transmit
the FPI, so there's no need to convert it.


Steven R. Newcomb, President, TechnoTeacher, Inc.
srn at

voice: +1 972 231 4098 (at ISOGEN: +1 214 953 0004 x137)
fax    +1 972 994 0087 (at ISOGEN: +1 214 953 3152)

3615 Tanner Lane
Richardson, Texas 75082-2618 USA

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