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Re: datatypes: new information - email delayed awaiting WG response

From: Graham Klyne <Graham.Klyne@MIMEsweeper.com>
Date: Wed, 03 Jul 2002 20:44:31 +0100
Message-Id: <5.1.0.14.2.20020703201857.03e35440@joy.songbird.com>
To: Brian McBride <bwm@hplb.hpl.hp.com>
Cc: RDF Core <w3c-rdfcore-wg@w3.org>

At 04:58 PM 7/3/02 +0100, Brian McBride wrote:

>I was about to send out the datatypes message to rdf interest, but I'm 
>concerned that we have new information that means I need to change it.
>
>Have we agreed that test A does not hold for untidy literals?  Patrick 
>has, and I think Jeremy has.  If so then I need to modify (simplify) the 
>message - tests B and C can be dropped.
>
>The reasons we might decide that test A does not hold are:
>
>   o it requires a special case in the reification machinery
>   o it requires a special case in the container machinery
>   o it interacts badly with rdfs:subPropertyOf
>
>http://lists.w3.org/Archives/Public/w3c-rdfcore-wg/2002Jul/0004.html
>http://lists.w3.org/Archives/Public/w3c-rdfcore-wg/2002Jul/0009.html

Hmmm... I could live with one special case (for reification), but I'm less 
comfortable with two (for containers as well).  I think it would be 
perfectly possible to have special semantics for these cases, but it starts 
to feel less reasonable.  Which, to me, makes the entailment:

     a someProp "lit" .
     b someProp "lit" .
|=
     a someProp _:x .
     b someProp _:x .

look less feasible in the absence of:

     a someProp "lit" .
     b anotherProp "lit" .
|=
     a someProp _:x .
     b anotherProp _:x .

But I do think this is a matter of taste, rather than a forced outcome.

As for:
>http://lists.w3.org/Archives/Public/w3c-rdfcore-wg/2002Jul/0011.html

I'm inclined to say "relax", but I'd be too tentative to be convincing.

If we have:

     a someProp "lit" .
     b someProp "lit" .
|=
     a someProp _:x .
     b someProp _:x .

I think it's pretty clear that:

    _:a dc:title "4th July" .
    _:b dc:date  "4th July" .
    dc:title rdfs:subPropertyOf dc:property .
    dc:date  rdfs:subPropertyOf dc:property .
|=
    _:a dc:property _:l .
    _:b dc:property _:l .

So the problem you raise is what happens when different datatypes are 
applied to dc:title and dc:date?  If the datatypes have no literal->value 
mappings in common, then I think that simply means the graph is not 
satisfiable.  I.e. there is no (DT-)interpretation that satisfies the 
antecedent so the entailment is trivially valid.

(Datatyping, as currently discussed, applies only to a specific property 
and not necessarily to its superproperties.)

#g


-------------------
Graham Klyne
<GK@NineByNine.org>
Received on Wednesday, 3 July 2002 18:07:56 EDT

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