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Re: Datatyping Summary

From: Dan Connolly <connolly@w3.org>
Date: 30 Jan 2002 09:41:44 -0600
To: Brian McBride <bwm@hplb.hpl.hp.com>
Cc: Jeremy Carroll <jjc@hplb.hpl.hp.com>, RDF core WG <w3c-rdfcore-wg@w3.org>
Message-Id: <1012405304.18171.35.camel@dirk>
On Wed, 2002-01-30 at 08:54, Brian McBride wrote:
> Ok Jeremy,
> 
> As I understand what you are suggesting here, is that under TDL, the rule 
> could be rewritten to get the desired effect, i.e. reflecting the "literal 
> is a pair" directly in an extended n-triples represention:
> 
>    <mary> <haircolor> (_, "red") .
> 
> and
> 
>    ?x <haircolor> (_, "red") => ?x <rdf:type> <redhead> .
> 
> one can conclude:
> 
>    ?x <rdf:type> <redhead> .
> 
> DanC - Do you buy this one.  Rewrite the rule and you get what you want.

I accept the reasoning above; it doesn't address my objection;
it' just shows that my example wasn't very good. Sergey's
example makes the point better:

--8<--

  _:f <rdf:type> <film> .
  _:f <dc:Title> "10" .
  <mary> <age> "10" .

Given a query:

  (?x <dc:Title> ?y) & (?z <age> ?y)
--8<--

As to the claim that query is irrelevant, I disagree;
it's clearly analagous to an entailment test:

premise:

  _:f <rdf:type> <film> .
  _:f <dc:Title> "10" .
  <mary> <age> "10" .

conclusion:

  _:x <dc:Title> _:y.
  _:z <age> _:y.

pass or fail?

Clearly when viewed in TDL-extended-N3 as above...

  _:f <rdf:type> <film> .
  _:f <dc:Title> (_:t1, "10") .
  <mary> <age> (_:t2, "10") .

it's not valid to conclude

  _:x <dc:Title> _:y.
  _:z <age> _:y.

The TDL proponents claim this is a feature: the two occurences
of "10" might indeed denote different things. I see it as a bug:
I think RDF users expect "10" to match "10".
This seems to put the two positions in pretty stark contrast.

-- 
Dan Connolly, W3C http://www.w3.org/People/Connolly/
Received on Wednesday, 30 January 2002 10:42:31 EST

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