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Re: mergeg in current Semantics ED

From: Peter Patel-Schneider <pfpschneider@gmail.com>
Date: Thu, 7 Mar 2013 14:56:37 -0800
Message-ID: <CAMpDgVwkgHrxsi9+BJO25Bjtb3uCRknvbz=JWUuPmEH8kEWK+A@mail.gmail.com>
To: Pat Hayes <phayes@ihmc.us>
Cc: RDF WG <public-rdf-wg@w3.org>
On Thu, Mar 7, 2013 at 2:41 PM, Pat Hayes <phayes@ihmc.us> wrote:

>
> On Mar 7, 2013, at 3:12 PM, Peter Patel-Schneider wrote:
>
> > I think that the current document makes the entailment not work.
> >
> > G1 is Ex p1(s1,x)
> > G2 is Ex p2(s2,x)
>
> No, its not. If they share a blank node, they must be in  the same scope;
> and the existential is defined at the scope, not at the graph, level. So
> under the conditions given by Antoine, the Ex is outside the conjunction of
> G1 and G2.
>

I see exactly the opposite of this in the current document.

"If E is an RDF graph then I(E) = true if [I+A](E) = true for some mapping
A from the set of blank nodes in the scope of E to IR, otherwise I(E)=
false."

So, consider I with I(s1) = s1, I(s2) = s2, I(p1) = p1, I(p2) = p2,
IEXT(p1) = {<s1,s1>}, IEXT(p2) = {<s2,s2>}
(add the other stuff to minimally turn this into a simple interpretation).

Then I(G1) = true, from the mapping A1:x->s1
and I(G2) =true, from the mapping A2:x->s2
but there is no mapping for x that makes I({G1,G2}) = true.

So, yes, the existential in {G1,G2} is global in the current document, but
that is precisely what makes the difference.

peter
Received on Thursday, 7 March 2013 22:57:04 GMT

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