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Re: Input sought on datatyping tradeoff

From: Drew McDermott <drew.mcdermott@yale.edu>
Date: Fri, 12 Jul 2002 18:12:54 -0400 (EDT)
Message-Id: <200207141533.g6EFXmi03476@pantheon-po03.its.yale.edu>
To: www-rdf-comments@w3.org
CC: drew.mcdermott@yale.edu

I have posted on rdf-logic why I don't think the questions below are
the right questions.  However, I can answer them under the assumption
that they are the right questions.

   A few simple test cases:

   Test A:

      <Jenny> <ageInYears> "10" .
      <John>  <ageInYears> "10" .

   Should an RDF processor conclude that the value of the ageInYears 
   properties for Jenny and John are the same?

Yes, because no matter how the argument to <ageInYears> is parsed, the
same input string must yield the same literal.  (Escape clause: If
<ageInYears> is allowed to consider its first argument, then I switch
to "No conclusion."  Perhaps <Jenny> and <John> are entities of
different types, which parse their <ageInYears> properties
differently.  I assume this is not allowed.)

   There are variations on this test which should be considered before answering.

   Test A2:

      <Jenny> <ageInYears> "10" .
      <Jenny> <testScore>  "10" .

   Should an RDF processor conclude that the value of Jenny's ageInYears 
   property is the same as the value of Jenny's testScore property?

No.  Nor can it conclude that they are different.

   Test A3:

      <Jenny> <ageInYears>   "10" .
      <Film>  <title>        "10" .

   Should an RDF processor conclude that the value of Jenny's age property is 
   the same as the value of the Film's title property?  

No.  As in case A2, it can't conclude they're not the same either.

   The answer must be the same for all three of these A tests.

I disagree; see above.

   These test cases only relates to the situation where there are no range 
   constraints on the properties.

Assuming nonmonotonicity is to be avoided, that's why we have to
respond "I don't know" in cases A2 and A3.  The situation in which
"there are no range constraints" is undefined in RDF, because you
could always discover some range constraints later, and nothing
concluded earlier can be removed.

   Now for a different kind of test.  How do the values of the two idioms relate?

   Test D:

      <Jenny>      <ageInYears> "10" .
      <ageInYears> rdfs:range xsd:decimal .

      <John>  <ageInYears>   _:a .
      _:a     xsdr:decimal   "10" .


   Should an RDF processor conclude that Jenny and John have the same 
   age?  

Yes.  

   [Note: in this example the range constraint is expressed using 
   rdfs:range.  We may have to introduce a special datatyping range property, 
   but that is an independent detail for now.]

   It is not possible to have the answers to Tests A and Test D both be 
   yes.  Either the A's can be yes or D can be yes, but not both.  We have to 
   decide which of these is the most important to have.

I don't see why they can't both be Yes.  (I've read Brian's message of
July 1 arguing that they can't, but I'll respond on the rdf-logic
mailing list.)

                                             -- Drew McDermott
Received on Sunday, 14 July 2002 11:33:55 GMT

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