# Re: Unresolvable URNs

David Robison (robison@nwnet.net)
Fri, 18 Feb 1994 10:29:12 -0800 (PST)

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    Date: Fri, 18 Feb 1994 10:29:12 -0800 (PST)

    From: David Robison <robison@nwnet.net>

    Subject: Re: Unresolvable URNs

    To: Jim McBeath <redback!jimmc@eskimo.com>

    In-Reply-To: <9402172203.AA28955@redback.>

    Message-Id: <Pine.3.89.9402181018.D11063-0100000@norman.nwnet.net>

A correction is in order here: ISBNs are not opaque. They are made up of
4 discrete sections: the first represents language/country; the second is
the publisher number; the third is the book number (simply and ordinal);
the last digit is a check digit.

This model is quite applicable to the URN scheme as the publisher is
assigned an identifire and it is up to them to correctly assign each
document a unique number within their range (i.e. publisher number). One
downside to the ISBN scheme is that the numbers are limited to 10 digits,
so a publisher that is assigned a many-digit number can only publish a
few title (no less than 10 [0-9]) with a certain publisher number. This
certainly has scaling problems.

On Thu, 17 Feb 1994, Jim McBeath wrote:

> I have been trying to understand how URNs will actually be used by
> comparing them to how references are generally used in printed media.
> I don't know if this is a valid comparison, but it seems like there
> must be something we can extract from the years of experience people
> have using printed references.
>
> Karen Sollins writes:
> > Resolution: It is quite possible that there will be URNs that
> > cannot be resolved for all time. Two reasonable situations in which
> > this may occur if a URN is created as a place holder for a resource
> > that does not yet exist or in the case that a resource is either
> > temporarily or permanently inaccessible (deleted, killed, etc.) In
> > this latter case, the fact that there was/is a reference may be
> > important, even if the resource is not currently accessible.
>
> In printed media, a reference to another document generally includes
> not only an opaque unique identifier (such as an ISBN number), but
> a small amount of additional information, such as Author and Title.
>
> Theoretically, only the ISBN is required, from which the referenced
> document can be retrieved. But what if the reference can not be
> resolved? With only an opaque identifier, the reader can get no information
> about the contents of the referenced document. With a name and an author,
> it is at least possible to have an inkling of what the document is about,
> and to attempt to chase down other related references, for example by
> the same author.
>
[stuff deleted]
>
> -Jim McBeath
> jimmc@eskimo.com
>
With a discrete and unique publisher number in the URN, you would have
important information in an otherwise unresolvable URN.

David Robison
robison@nwnet.net

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