Re: Web Rule Language - WRL vs SWRL

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Bijan Parsia wrote:

> On Jun 22, 2005, at 1:18 PM, Jos de Bruijn wrote:
>
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>> Jim Hendler wrote:
>>
>>> Jos-
>>> that's not quite right as I understand it - to use an example from
>>> the
>>
>> paper I cited -
>>
>>>
>>> Given an ontology containing only a single RDF triple:
>>> <#pat> <#knows> <#jo>.
>>> the answer to a query asking if pat knows exactly one person would be
>>
>> "no" under
>>
>>> RDF's open world semantics, but "yes" under the closed world
>>> semantics
>>
>> of Datalog.
>>
>>>
>>> there's no negation explicit here.
>>
>>
>> If you would write down the query you mentioned, you would see that
>> the query includes negation.
>
> [snip]
>
> That's the point, right? Queries that you might expect to return the
> same results on that data *don't* depending on the semantics you
> have for the *data*. Of course your query language might be (will
> be!) more expressive than your data language (see SQL).

No! As I showed in an earlier email, the ground entailments for both
semantics are *equivalent* and thus the queries would return the same
result.


Best, Jos

>
> So the question is how to make this work. Are we already in the land
> of multiple extensions (in the default theory sense)? One hopes not.
>
> One reason to be less shy of, e.g., NAF in query languages rather
> than in the data is that the author of the query is most likely the
> person evaluating the query, so its context is rather clearer.
>
> Cheers,
> Bijan.
>
>
>


- --
Jos de Bruijn, http://www.uibk.ac.at/~c703239/
+43 512 507 6475         jos.debruijn@deri.org

DERI                      http://www.deri.org/
- ----------------------------------------------

Only two things are infinite, the universe and
human stupidity, and I'm not sure about the
former.
    -- Albert Einstein
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Received on Wednesday, 22 June 2005 18:06:38 UTC