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   Re: Public Identifiers

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  • From: John Cowan <cowan@locke.ccil.org>
  • To: xml-dev@ic.ac.uk
  • Date: Mon, 21 Sep 1998 13:44:41 -0400 (EDT)

Steven R. Newcomb scripsit:

> * 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, 

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".

My understanding is that the widespread use of unregistered FPIs
merely reflects the lack of easy access to registration until recently.

> > # 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.

I think that Sears itself might be quite unhappy about people invading
its FPI namespace in this fashion.  Such an FPI is more like a
prose description of the resource.

>   (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.)

I think that the identifiers of ISO 9070 are intended 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.

Not so.  You take that sentence out of its context, which makes clear that
it's quite possible for an URN to never have any corresponding URLs.

> In the scenario I'm asking about, there is never any need to transmit
> the FPI, so there's no need to convert it.

I don't understand this point.  An FPI that's never transmitted
remains within the brain of its inventor only.  The point of 
URI-encoding is simply to make clear where the delimiters of the URI are.
Allowing embedded spaces is good for human readability, but not ffor

John Cowan					cowan@ccil.org
		e'osai ko sarji la lojban.

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