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

HTTP Range Middle ground?

From: Paul Prescod <paul@prescod.net>
Date: Wed, 30 Jul 2003 01:36:53 -0700
Message-ID: <3F2783A5.4040209@prescod.net>
To: Norman Walsh <Norman.Walsh@Sun.COM>, www-tag@w3.org

Norman Walsh wrote:
> ...
> 
> Some people (I won't attempt to put words in your mouth) respond to
> this by saying that the machines won't be able to tell. But machines can't
> tell anything. I've lost the focus about why disambiguating
> 
>   <http://www.tbray.org/ongoing/misc/Tim> rdf:type ex:Person .
>   <http://www.tbray.org/ongoing/misc/Tim> rdf:type ex:WebPage .
> 
> which (might) conflict is anymore important or difficult or different than
> disambiguating
> 
>   <http://www.example.com/kr#foo> rdf:type ex:Peacock .
>   <http://www.example.com/kr#foo> rdf:type ex:GardenSlug .
> 
> Surely garden slugs and peacocks are disjoint.

The second two statements are in straightforward contradiction. The SW
agent can merely report it and ask the user to choose which statement to
discard.

The first two statements are not meant to be in contradiction. If you
throw out the first statement then the resource is useless as a Person
(presumably the whole point of the URI). If you throw out the second
statement then the SW agent must discard the fact that the URI can be
dereferenced. But more important, the agent must discard statements
about the resource that only apply to WebPages, not persons, like
statements about available MIME types or reliability.

If we throw out neither statement then we must state the set of Persons
and WebPages is not disjoint. But your common sense said that they were
disjoint (like Peacocks and GardenSlugs).

I propose that the Semantic Web world merely say that it is a BAD
PRACTICE to assert that HTTP URIs are anything other than "HTTP
Resources" because it becomes impossible to make assertions about them
AS HTTP resources without ambiguity.

At the same time, the TAG could invent some particular syntax whereby
one URI could be said to represent the HTTP responder for another URI
and vice versa. Then we could say that:

<http://www.tbray.org/ongoing/misc/Tim> rdf:type ex:Person .
<http://www.tbray.org/ongoing/misc/Tim/resp> rdf:type ex:WebPage.

<http://www.tbray.org/ongoing/misc/Tim/resp> tag:responderResourceFor
<http://www.tbray.org/ongoing/misc/Tim>.

But a better (less confusing) way of handling the same situation would be:

<http://www.tbray.org/ongoing/misc/Tim> rdf:type ex:WebPage .
<http://www.tbray.org/ongoing/misc/Tim#Tim> rdf:type ex:Person.

<http://www.tbray.org/ongoing/misc/Tim> tag:responderResourceFor
<http://www.tbray.org/ongoing/misc/Tim#Tim>.

If neither statement is present, then we use the current SW default
which is that the base HTTP URI is the responder URI for a resource with
a hash-mark following it. If there is no hash mark then it is impossible
to talk about one of the two resources until somebody mints an
appropriate URI.

  Paul Prescod
Received on Wednesday, 30 July 2003 04:37:03 UTC

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