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RE: [moved] RE: unsupported datatypes

From: Gary Ng <Gary.Ng@networkinference.com>
Date: Wed, 16 Jul 2003 15:28:57 +0100
Message-ID: <3BE4D3F0FB726240966DEF40418472B53E9530@ni-lon-server1.ad.networkinference.com>
To: "Jim Hendler" <hendler@cs.umd.edu>, "Ian Horrocks" <horrocks@cs.man.ac.uk>
Cc: <public-webont-comments@w3.org>

Yes, of course.

Cheers,

G

> -----Original Message-----
> From: Jim Hendler [mailto:hendler@cs.umd.edu]
> Sent: 16 July 2003 14:42
> To: Gary Ng; Ian Horrocks
> Cc: public-webont-comments@w3.org
> Subject: [moved] RE: unsupported datatypes
> 
> Gary-
>   Ian has suggested that he is happy to continue this discussion on
> www-rdf-logic, is that okay?
>   thanks
>   Jim Hendler
> 
> 
> At 6:26 PM +0100 7/15/03, Gary Ng wrote:
> >>  -----Original Message-----
> >>  From: Ian Horrocks
> >>  Sent: 15 July 2003 18:02
> >>  To: Gary Ng
> >>  Cc: public-webont-comments@w3.org
> >>  Subject: Re: unsupported datatypes
> >>
> >>  On July 15, Gary Ng writes:
> >>  >
> >>  >
> >>  > Another question, this time about unsupported datatypes.
> >>  >
> >>  > In the reference doc, it says:
> >>  >
> >>  > "For unsupported datatypes, lexically identical literals should
be
> >>  > considered equal, whereas lexically different literals would not
be
> >>  > known to be either equal or unequal. Unrecognized datatypes
should
> >be
> >>  > treated in the same way as unsupported datatypes."
> >>  >
> >>  > The first half of the sentence would suggest to treat a literal
of
> >>  > unknown type as just a string. However, I am not entirely sure
what
> >is
> >>  > expected from a reasoner with respect to the behaviour of "would
not
> >be
> >>  > known to be either equal or unequal".
> >>
> >>  Unknown or unrecognised datatypes are treated as being the lexical
> >>  form (a string) of some unknown datatype. It is obviously the case
> >>  that, whatever the datatype, identical lexical forms map to the
same
> >>  element of the value space, and can thus be considered equal. For
> >>  non-identical lexical forms, however, it *cannot* be assumed that
they
> >>  do not map to the same element of the value space and are thus
> >>  unequal.
> >>
> >>  E.g., the lexical forms "1.0" and "01.00" would map to the same
value
> >>  (and thus be considered equal) in some datatypes (e.g., decimal),
but
> >>  not in others (e.g., string).
> >>
> >Yes, I got that.
> >
> >But from a practical point of view of handling values from an
> >unsupported datatype within a reasoning tool, this sounds like I
can't
> >even implement them as strings because since two different strings
would
> >be considered unequal. So the question is, how should I implement
them?
> >
> >Consider the following:
> >
> ><Measurement rdf:ID="a_measurement">
> >	<hasAValueOf
> >rdf:datatype="someUnsupportedType">XYZ</hasAValueOf>
> ></Measurement>
> >
> ><Measurement rdf:ID="b_measurement">
> >	<hasAValueOf
> >rdf:datatype="someUnsupportedType">ABC</hasAValueOf>
> ></Measurement>
> >
> >by the definition, "XYZ" and "ABC" are neither equal nor unequal.
> >So what should be the answer to the following question?
> >
> >Retrieve all instances of (complementOf(exists hasAValueOf XYZ))
> >
> >Because we cannot *prove* that XYZ = or != to ABC, thus
> >The answer would be empty. Am I correct?
> >
> >If I am correct, then this behaviour is the same as if XYZ and ABC
are
> >classes/instances. So really we can't implement values from
unsupported
> >datatypes as strings.
> >
> >Correct?
> >
> >G
> 
> --
> Professor James Hendler
hendler@cs.umd.edu
> Director, Semantic Web and Agent Technologies	  301-405-2696
> Maryland Information and Network Dynamics Lab.	  301-405-6707
(Fax)
> Univ of Maryland, College Park, MD 20742	  *** 240-277-3388
(Cell)
> http://www.cs.umd.edu/users/hendler      *** NOTE CHANGED CELL NUMBER
***
Received on Wednesday, 16 July 2003 10:29:08 GMT

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