W3C home > Mailing lists > Public > www-rdf-logic@w3.org > July 2002

Re: Input sought on datatyping tradeoff

From: Brian McBride <bwm@hplb.hpl.hp.com>
Date: Sat, 13 Jul 2002 10:43:03 +0100
Message-Id: <5.1.0.14.0.20020713101644.027ca320@15.144.25.13>
To: Drew McDermott <drew.mcdermott@yale.edu>, www-rdf-logic@w3.org

At 18:32 12/07/2002 -0400, Drew McDermott wrote:


>    [Thomas Passin]
>    >Test A1 uses the same predicate and so could be compared.
>
>    [Brian McBride]
>    We considered this, and talked ourselves out of it.
>
>       http://lists.w3.org/Archives/Public/w3c-rdfcore-wg/2002Jul/0011.html
>
>I don't think this settles the issue.

I think that's right.  From my perspective, it was more of judgement call 
than a slam dunk argument.  The subPropertyOf issues and some other stuff 
to do with reification and container membership taken together looked 
unpromising.

[...]

>    [and here I edit a little, possibly completely missing Brian's point]
>
>       _:a dc:property "4th July"
>       _:b dc:property "4th July"

The original was:

       _:a dc:property _:l .
       _:b dc:property _:l .

emphasizing the point that the denotation of the object of each statement 
must denote the same thing.


>Now we have the same predicate, and hence "4th July" must denote the
>same entity, contrary to our previous conclusion.

Yes thats the point.


>I must indeed be missing something.  We've been assuming that for
>every property (here, dc:property in particular) there is a parser
>that unambiguously specifies how to interpret the strings that occur
>as its values, even if we don't know what that parser is.

I wasn't aware I was making that assumption, but maybe I was.  I think I 
was assuming that the model theory will say there must be something in the 
domain of discourse the _:l binds to.

>   Well, even
>if we don't know what it is in this case, surely we must be able to
>spell out a candidate or two.  But as far as I can see there is no
>candidate, because in the case of _:b it would have to transform "4th
>July" into one value, and in the case of _:a into another.

Yup.


>Hence the triples above are inconsistent,

There's the rub.  They are inconsistent if we have untidy literals (i.e. 
the literal "lit" can denote different things in different statements) and 
the rule:

   _:a <prop> "lit" .
   _:b <prop> "lit" .

|=

    _:a <prop> _:l .
    _:b <prop> _:l .

and we have a choice from 3:

   o have tidy literals
   o keep the rule and require subProperties to have "consistent" datatypes
     with their super properties
   o abandon the rule, in which case the answer to test case A1 is "NO, a 
processor has
     insufficient information to decide".

We chose to eliminate the rule.  We are asking for help choosing between 
the other two options.

Brian
Received on Saturday, 13 July 2002 05:45:15 GMT

This archive was generated by hypermail 2.2.0+W3C-0.50 : Monday, 7 December 2009 10:52:42 GMT