W3C home > Mailing lists > Public > uri@w3.org > January 2002

Re: URx Questions

From: Patrick Stickler <patrick.stickler@nokia.com>
Date: Wed, 23 Jan 2002 12:43:47 +0200
To: URN <urn-ietf@lists.netsol.com>, URI <uri@w3.org>
Message-ID: <B8746083.C1BC%patrick.stickler@nokia.com>
On 2002-01-22 19:38, "ext Tim Kindberg" <timothy@hpl.hp.com> wrote:

> At 04:26 PM 1/22/2002 +0200, Patrick Stickler wrote:
>> I fully appreciate the benefit of guarunteed global and temporal
>> uniqueness (hence support for UUIDs), but I feel that there are
>> other means of anchoring names in time, not just by date, such
>> as version numbers, and there is nothing to prevent you from including
>> a date in an 'hrn:' root, similar to 'tag:' -- it simply isn't
>> manditory.
> But 'version numbers' don't necessarily cross organisations whereas dates
> do. Our view is that you have to mandate some type of framework for the
> coherence of the name space.

But "mandates" in general seldom succeed. You must support the
practices and traditions of the minting authorities.

It is up to the minting authority to determine what is needed,
and in my experience, it is seldom that the current practice
does not suffice.

Forcing all organizations worldwide to change the way they
construct identifiers (apart from educating them on the issues
relating to globally and temporally unique idenfiers in a
web context and showing them how they can best achieve that)
is not going to work.

Most large organizations have very well established methods for
achieving unique names within the scope of that organization, and
the 'hrn:' scheme is a way for them to capture those methods in
a URI without having to re-engineer those methods or processes
(unless they choose to).

>>> As for the hierarchical nature of hrns -- sure, hierarchies are nice. But
>>> why mandate a syntax to that extent for the 'local' part of the identifier?
>>> It's nobody else's business; it just has to be unique.
>> I'm not sure I follow you -- though per my unsure understanding,
>> you would like to leave everything beyond the authority portion
>> opaque?
> That's what we do.

But why should the rest of the world also live with that
restriction. Many folks *need* hierarchical identifiers.
>> Well, there's no restriction about having "local" syntax for
>> partitioning of any sort, and you can have any valid URI string
>> (sans '/' characters) in your local part, with just one level
>> of naming.
> But my point is: why frame or constrain where there is no global need to do
> so? We should agree on as little as possible (Occam's Razor for naming
> schemes).

Where on earth do you get the idea that there is no need to
do so. Just because you don't need to, or just because
everybody doesn't need to, does not mean it is not a widespread
>> Having a standardized representation for hierarchy, though,
>> is very useful for scoping identifier models which define the
>> identity of resources in terms of superordinate context.
>> E.g. work/expression/realization/instance is a common hierarchy
>> in the library/literature fields.
> I'm happy to let such communities develop their own standards but it's none
> of my business.

Then why are you commenting on the 'hrn:' scheme?

It is a standard for global naming for communities which
desire hierarchical URNs.

If you don't care about hierarchical URNs, then you
shouldn't care about the 'hrn:' URN scheme. No?

>> I will admit, however, that the intended purpose and utility
>> of the 'tag:' and 'hrn:' URN schemes do overlap, and one
>> advantage of the 'hrn:' scheme (having of course a biased
>> view) is that the semantics of the 'hrn:' scheme expect an
>> instance of that scheme to denote a retrievable digital
>> resource whereas the 'tag:' URN/URT scheme may be used for
>> either digital or non-digital resources, which introduces
>> problems for software applications needing to decide what
>> to do with one.
> One of our intended use models is indeed that people can attach tags to
> physical entities but the point of doing so is for users to retrieve
> digital resources from them
> (http://www.hpl.hp.com/techreports/2001/HPL-2001-95.html). So I don't see
> the difference.

I don't follow. How do you retrieve a digital resource
"from" a non-digital resource?

Do you mean e.g. a book which may both be printed and available
in digital form?

In such a case, we have several "entities", we have the abstract
work, and an expression of that work (e.g. in a given language),
and for that expression, two manifestations, one which is physical
and one which is digital. Only the last, the digital manifestation,
would be a URN denoted resource, leading from the definition of
a URN as an indirect point of access for a digital (web) resource.

C.f. http://www.ifla.org/VII/s13/frbr/frbr.htm



Patrick Stickler              Phone: +358 50 483 9453
Senior Research Scientist     Fax:   +358 7180 35409
Nokia Research Center         Email: patrick.stickler@nokia.com
Received on Wednesday, 23 January 2002 05:43:01 UTC

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