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

Norman Walsh wrote:
>
> I don't see how the assertion that "each use of the URI by definition
> talks about the same concept" can be justified.

If by "concept" you mean "resource" then it is true by definition and
according to the RDF model theory http://www.w3.org/TR/rdf-mt/

If by "concept" you mean _graph_ which might include a resource and web of
resources connected by arcs, then the fact that there might be any number of
_unconnected_ graphs, is alluded to by RDF but not dealt with in infinite
detail.

I'd say that the Web as we define it is a _single graph_ of interconnected
resources, at least that's how I'd define the part of the Web that is
reachable by, say, Google. Now RDF as it stands today might have some
problems dealing with that but that is another story (RDF lacks the notion
of "context").

What I would say to resolve this is that:

Every use of a single URI(ref) refers to the same resource but perhaps in
different contexts.

>
> | <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.
>
> Well, you've used the same name. To the extent that URIs are absolute
> and context-independent, you can say they're the same, but I thought
> the point of statements like this is that they could be used to make
> assertions about things, not just the names of things.

In RDF there are named things (resources) which are denoted by a URIref, and
unnamed things (anonymous resources or b-nodes -- "b" for "blank"). Under
the RDF model theory (at least as under the WD as of today) its not possible
to dissociate a named resource from its name.

>
> |> ...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.
>
> Including some inconsistent and mutually exclusive things?

Sure, inconsistencies are not a problem to deal with -- they are just
logically false. That is to say that you and other people might say anything
they wish to about anything -- we just might not believe everything we hear
about something -- particularly if there is a contradiction, we know
something is incorrect.

Jonathan

Received on Saturday, 3 August 2002 18:59:23 UTC