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Re: OWL2 RDF mapping and skolemization [was Re: OWL equivalentClass question]

From: Peter F. Patel-Schneider <pfpschneider@gmail.com>
Date: Sun, 15 Jul 2012 22:46:50 -0400
Message-ID: <5003809A.7030301@gmail.com>
To: nathan@webr3.org
CC: David Booth <david@dbooth.org>, Pat Hayes <phayes@ihmc.us>, Alan Ruttenberg <alanruttenberg@gmail.com>, Michael Schneider <schneid@fzi.de>, semantic-web@w3.org

On 07/15/2012 10:26 PM, Nathan wrote:
> David Booth wrote:
>> Correction . . .
>>
>> On Sun, 2012-07-15 at 19:10 -0400, David Booth wrote:
>>> Hi All,
>>>
>>> Thanks for your comments.  To get to the crux of the matter . . .
>>> On Fri, 2012-07-13 at 23:35 -0500, Pat Hayes wrote:
>>>> [ . . . ] If you start with a graph G containing a bnode and skolemize
>>>> it to get another graph GS where the bnode has been replaced by a URI,
>>>> then G does not entail GS. 
>>> Unless we're making a closed world assumption, that sounds wrong to me,
>>
>> I read Pat's statement backwards, so my response above said the opposite
>> of what I meant (as Peter pointed out).  What I *meant* was that I think
>> GS should entail G . . . 
>
> it does?

Yes.  Skolemization adds information, so a skolemized graph (GS) entails the 
original (G).

The "trick" of skolemization is that this additional information can be proven 
to be irrelevant for many entailments, thus letting GS stand in for G in many 
situations.

peter
Received on Monday, 16 July 2012 02:47:20 UTC

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