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Re: a few issues with daml+oil+concrete (XMLSchema Datatypes)

From: Peter F. Patel-Schneider <pfps@research.bell-labs.com>
Date: Fri, 16 Feb 2001 09:40:53 -0500
To: sandro@w3.org
Cc: www-rdf-logic@w3.org, ht@w3.org
Message-Id: <20010216094053K.pfps@research.bell-labs.com>
A few comments on Sandro's message.

From: Sandro Hawke <sandro@w3.org>
Subject: a few issues with daml+oil+concrete (XMLSchema Datatypes)
Date: Thu, 15 Feb 2001 23:11:02 -0500

> 
> 2.  The proposal treats datatypes as if they were the classes which
>     conventionally have the same name (eg "integer"), but according to
>     the XMLSchema spec, they are not.  For example, [2] contains:
[...]
>     which both seem to be treating these XMLSchema datatypes (integer
>     and decimal, respectively) as if they were the classes of numbers.
> 
>     But the XML Schema Datatypes spec [4] says that "a datatype is a
>     3-tuple, consisting of a) a set of distinct values, called its
>     value space, b) a set of lexical representations, called its
>     lexical space, ..."  
[...]

I don't see this as a problem.  An XMLSchema datatype may be a three-tuple,
not a set, but classes are not sets.  Just as we have an type relationship
between an abstract object and an abstract class, which is modelled in the
model-theoretic semantics as set membership, we can have a similar
relationship between the integer 10 and the XML schema datatype 
http://www.w3c.org/xml/xmlschema#integer, which is also modelled in the
model-theoretic semantics as set membership.

> 3.  Using the property rdf:value to link from a point in the value
>     space (eg 10) to a point in the lexical space (eg "10") seems
>     completely backwards.   That's saying:
> 
>           the number 10 has a value which is the string "10"
> 
>     when the correct form (IMHO) is
> 
>           the number 10 has a lexical representation which is the 
>           string "10"
> 
>     I know rdf:value is given in RDF M&S, but that doesn't make it
>     right.  We need a property lexicalRepresentation (and probably
>     canonicalLexicalRepresentation) to be clear here.  [...]

Agreed.  I also think that this is the wrong way around.  However rdf:value
is used for precisely this relationship in RDF M&S.  One other reason for
using rdf:value is that it is shorter than rdf:lexicalRepresentation.

>    -- Sandro Hawke

Peter Patel-Schneider
Received on Friday, 16 February 2001 09:41:48 GMT

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