W3C home > Mailing lists > Public > www-tag@w3.org > July 2003

Re: erratum Re: resources and URIs

From: Jonathan Borden <jonathan@openhealth.org>
Date: Mon, 21 Jul 2003 10:46:56 -0400
Message-ID: <00e801c34f96$f22ba0a0$b6f5d3ce@svhs.local>
To: "Michael Day" <mikeday@yeslogic.com>, "pat hayes" <phayes@ihmc.us>
Cc: <www-tag@w3.org>

Actually ...


>
> >  > Think about it: it that were true, then by writing "1404 West La Rua
> >>  St., Pensacola" you would have created a link to something that does
> >>  not exist, which is impossible.
> >
> ><a href="http://this.does.not.exist.com/index.html"> Link </a>
> >
> >Have I not just created a link to something that does not exist?

You have created a link to a resource which may or may not return a
representation on dereferencing the URI ... I'd assume that it would return
a 404 ... BUT ... by creating the URI you actually do 'create' a resource.
It does 'exist' as the resource whose URI is
http://this.does.not.exist.com/index.html ... now Pat uses an example of an
address *for the physical world* which may or may not physically exist. In
URI space, as long as the URI is valid, the resource 'exists'. There is
nothing preventing the owner of 'exist.com' from creating such a resource
... the only issue I can see here is that since you don't own 'exist.com'
the URI you've created is 'illegal'. URI space as opposed to 'physical
space' contains a point for every legal URI ... such points might be called
'resources', and for every URI there does exist a resource (in URI space).

We might similarly say that "1404 West La Rua St., Pensacola" is an
_invalid_ address per the rules of either the postal service or of
Pensacola, FL ... just as per the rules of "exist.com"
http://this.does.not.exist.com/index.html might be invalid.

...
>
> >A citation of a book giving page number, paragraph and line number is
> >still a link, even if the book no longer exists. Not all links can be
> >traversed or dereferenced.
> >
> >"Creating a link to" == referencing, in some cases quite optimistically
>
> Ah.  OK, with that usage, then I would agree; but that is a VERY
> strange usage of "link", at least to one reader.  And I think it is
> highly misleading, since "link" usually *does* imply at least the
> possibility of dereferencing, in principle, in an ideal world, etc.;
> whereas this sense of 'link' to simply mean 'refer to' clearly never
> has, and never had, any such implication.  (What a referring name
> enables you to do is to *think* and *talk* about something, not to
> actually get your hands on it.)

In the Web Architecture, you never can actually get your hands on the
resource, rather the representation. I don't see the problem with: "create a
link to" == reference.

In any case the URI "urn:isbn:xxx" does allow you to reference a book, and
using this URI you might be able to 'dereference' a physical copy of the
book i.e. via an indirection service such as amazon.com


With this sense of 'link' it is
> clearly just a mistake to think that there must always be a unique
> thing 'linked to', for example: notoriously, one can refer to things
> that do not and never have existed, and one can, and often does,
> refer ambiguously.

right an such resources (that never have physically existed) may indeed have
representations e.g. a picture of a unicorn, or a written description.

Jonathan
Received on Monday, 21 July 2003 10:47:04 UTC

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