W3C home > Mailing lists > Public > www-tag@w3.org > August 2002

Re: [httpRange-14] What do HTTP URIs Identify?

From: Jonathan Borden <jonathan@openhealth.org>
Date: Thu, 1 Aug 2002 22:53:05 -0400
Message-ID: <005601c239cf$ba15f590$0201a8c0@ne.mediaone.net>
To: "Tim Bray" <tbray@textuality.com>, <www-tag@w3.org>

Tim Bray wrote:


>
> Roy T. Fielding wrote:
> ...As such, allowing the
> > identifier to identify more than one concept is a non-starter.
>
> Er... and how do you disallow identifiers from identifying whatever
> people think they identify?

A slightly subtle point, but when we say that a URI necessarily identifies
only one concept, this is saying that the _name_ of the concept is the URI.
Now people may assert different things about the concept, and these
assertions may be contradictory, but they are identifying the same concept
if they use the same name for the concept, i.e. the same URI.

> A single set of assertions that need to be
> internally consistent had better use the same URIs to identify the same
> things.  But across the broad information space of the web, how do can
> you ever sustain a promise that a URI will be used for only one concept?

Across the broad information space of the Web, the problem is sustaining any
"promise" that what each person says about the URI will be consistent. But
again the name of the concept is the URI so each use of the URI by
definition talks about the same concept.
>
> This gives TBL all sorts of grief, but I think that it is *inevitable*
> that there will be places where different people use the URI to identify
> different things.

By _thing_ perhaps you mean "set of defining assertions": that might indeed
be the case. By convention the name of the thing is the URI, so the URI
always identifies the same _thing_. It may be inevitable that different
people will make different assertions about a resource. e.g.

<rdf:Description rdf:about="http://example.org">
    <ex:Color rdf:resource="#Red"/>
</rdf:Description>

and somewhere else

<rdf:Description rdf:about="http://example.org">
    <ex:Color rdf:resource="#Red"/>
</rdf:Description>

The _thing_ i.e. http://example.org is the same, even though the statements
made might be contradictory.

> ...The
> Semantic Web has to be able to tolerate the fact that you can't know
> what a resource is, and thus different parties may not have a shared
> perception of this, just like the Web needed 404 to work. -Tim
>

On the Semantic Web you might not ever know everything there is to know
about a resourse, but you can know some things.

Jonathan
Received on Thursday, 1 August 2002 23:08:46 UTC

This archive was generated by hypermail 2.3.1 : Wednesday, 7 January 2015 15:32:33 UTC