Public Identifiers

Chris Maden crism at
Tue Sep 22 16:50:07 BST 1998

[Steven R. Newcomb]
> [John Cowan:]
> > Global uniqueness *is* a requirement of URNs, in the sense that
> > two distinct things ought not be described by the same URN, and
> > someone has to define what counts as "distinct things".
> OK. I necessarily conclude from your answer that URNs can't do what
> FPIs can do.

I am not sure how this follows.  Are you saying that two distinct
things *ought* to be described by the same FPI?  I'm having a hard
time thinking of a case in which this would be a good idea, except
maybe -//crism//DOCUMENT Random Text of the Day//EN, in which case the
FPI does, in some sense, point to a single resource (the semantic
concept of a randomly selected document).

> > My understanding is that the widespread use of unregistered FPIs
> > merely reflects the lack of easy access to registration until
> > recently.
> My understanding is that there is a need to refer to things that
> nobody has registered and that nobody who needs them to be
> registered has the authority to register.  Surely you're not
> proposing that Joe User should take it upon himself to register
> Sears and/or it's 1922 Farm Catalog on behalf of Sears, if Sears
> hasn't done this already for itself.

I don't understand this statement.  There is a need to refer to things
that nobody has registered, yes.  But you then say that Joe User
shouldn't register Sears, but that's exactly what he did in your
-//Sears//... example.  If Sears has not created an FPI for their 1922
catalog, then Joe User should say -//Joe User//NONSGML Sears Roebuck
and Co. 1922 Catalog//EN.

> I gather from what you say, however, that URNs can only be used to
> reference things that their owners have arranged to be referencable
> via URIs,

This is a truism, since URNs are a subset of URIs.  I think you meant
URLs, but...

> by going to the expense and trouble of registering themselves and/or
> their published information assets.

This isn't true.  The URN spec, as John quoted, specifically allows
the case of URNs that are not resolvable to a concrete electronic
resource.  And since FPIs can be used as URNs,
is a perfectly legitimate URN that points to the lump of paper in my

<!ENTITY crism PUBLIC "-//O'Reilly//NONSGML Christopher R. Maden//EN"
"<URL> <TEL>+1.617.499.7487
<USMAIL>90 Sherman Street, Cambridge, MA 02140 USA" NDATA SGML.Geek>

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