Re: owl:sameAs - Is it used in a right way?

Hi David,

We've discussed this in the past. You confuse what a uri refers to with the
framework by which a reasoner tries to figure out what entailments can be
made given some set of assertions.

It's as if I say something about my friend Jonathan Rees, and you think you
have sanction to interpret what I say to be about some other Jonathan Rees,
because I wasn't specific enough to narrow down the set of Jonathan Reeses
to just one.

-Alan


On Sunday, March 17, 2013, David Booth wrote:

> Hi Alan,
>
> On 03/16/2013 01:49 PM, Alan Ruttenberg wrote:
>
>> David's assertion that a uri can mean different things in different
>> graphs is an opinion
>>
>
> An opinion?  It is direct consequence of standard RDF Semantics!  Read the
> spec:
> http://www.w3.org/TR/rdf-mt/
> The RDF semantics is only defined for a *given* RDF graph.  It does not
> constrain a URI's resource identity across *different* graphs.  And here is
> a trivial existence proof that demonstrates that a URI does *not*
> necessarily denote the same resource in different graphs.
>
> Graph 1 (assuming standard owl: prefix):
>
>   <http://example/h> a <http://example/WhiteHorse> .
>   <http://example/WhiteHorse>
>        owl:disjointWith <http://example/BlackHorse> .
>
> Graph 2:
>
>   <http://example/h> a <http://example/BlackHorse> .
>   <http://example/WhiteHorse>
>        owl:disjointWith <http://example/BlackHorse> .
>
> Each graph (by itself) has satisfying interpretations per standard RDF
> (and OWL) semantics.  And <http://example/h> denotes a resource in each
> graph.  But clearly it denotes a *different* resource in each graph.
>
>  that does not concur with either the
>> web specifications
>>
>
> Correct.  As I pointed out, the AWWW's statement that "a URI identifies
> one resource" is a good goal, but it does not concur with standard RDF
> semantics.
>
> nor the goals they were built to satisfy. Caveat emptor.
>
> Not true!  As I said before, I *agree* with the goal stated in the AWWW,
> that a URI should denote one resource!  But that does not change the
> reality: that a URI does *not* necessarily denote only one resource.
> I also think world peace is a good goal, but it is *not* the reality.
>
> If we're going to make the semantic web work, we need to keep the goals in
> mind while *also* recognizing the reality.  Facing reality should not be
> construed as dismissing the goals.  We cannot simply wish the reality away.
>  We need to do the engineering to make it work.
>
> David
>