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Re: Datatyping Summary

From: Patrick Stickler <patrick.stickler@nokia.com>
Date: Wed, 30 Jan 2002 18:27:46 +0200
To: ext Brian McBride <bwm@hplb.hpl.hp.com>, RDF Core <w3c-rdfcore-wg@w3.org>
Message-ID: <B87DEBA2.CC24%patrick.stickler@nokia.com>
On 2002-01-30 16:47, "ext Brian McBride" <bwm@hplb.hpl.hp.com> wrote:


>>> Jeremy/Patrick:  Do you accept that without the range constraint, DanC is
>>> correct?
>> 
>> I do not accept that this is correct.
> 
> The question was:
> 
> DanC assserts that under TDL, given
> 
>  <mary> <haircolor> "red" .
> 
> and a rule:
> 
>  ?x <haircolor> "red" => ?x <rdf:type> <redhead> .
> 
> one cannot conclude
> 
>  <mary> <rdf:type> <rdfhead> .
> 
> Is he correct.  Patrick responds:
> 
>  I do not accept that this is correct
> 
> and from the text that follows, I believe that Patrick means "yes, this is
> correct".
> Patrick, please can you confirm.

It IS possible to conclude the specified inference,
based on string comparison of literals, which TDL
supports.

Therefore, I do NOT agree with Dan that you
CANNOT conclude that inference.

(BTW,I'm not shouting ;-) I'm just stressing the
important bits, since there seems a perpetual
confusion about exactly what I am disagreeing
with ;-)

>>> Given a query:
>>> 
>>>  (?x <dc:Title> ?y) & (?z <age> ?y)
>>> 
>>> existing applications will return:
>>> 
>>>  ?x = _:f, ?y = "10", ?z = <mary>
>>> 
>>> Under TDL, they would return null.
>>> 
>>> Sergey:  Does this version of the issue illustrate your point?
>>> 
>>> Jeremy/Patrick:  Do you accept this analysis; would the query return null
>>> under TDL?
>> 
>> I've provided a response to this in
>> 
>> http://lists.w3.org/Archives/Public/w3c-rdfcore-wg/2002Jan/0365.html
> 
> My reading of your response is that you agree that under TDL, the query
> would return null.  Is that correct.

Yes and no.

It's not an issue for TDL, it's an issue for the query
engine. If the query is based on string comparison of
literals only, then it will not return null, but will
bind ?y to the literal string "10" (which IMO is a
logical error).

If the query engine is comparing values, it will return
null.

TDL does not mandate either result. It allows for either.
(and, as Jeremy has pointed out, that is a benefit)
 
Patrick

--
               
Patrick Stickler              Phone: +358 50 483 9453
Senior Research Scientist     Fax:   +358 7180 35409
Nokia Research Center         Email: patrick.stickler@nokia.com
Received on Wednesday, 30 January 2002 11:27:03 EST

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