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Re: Alan Ruttenberg: Re: notes from OWL and RIF datatype coordination meeting

From: Chris Welty <cawelty@gmail.com>
Date: Tue, 17 Feb 2009 23:05:34 -0500
Message-ID: <499B890E.6080503@gmail.com>
To: Sandro Hawke <sandro@w3.org>
CC: public-rif-wg@w3.org, Alan Ruttenberg <alanruttenberg@gmail.com>, Boris Motik <boris.motik@comlab.ox.ac.uk>

Alan,

As I mention on our call, there are plenty of scientists and engineers who will 
dispute your abstract notion of  "mathematical properties of numbers".  Floats 
and decimals *are* different, and represent different things. For example, when 
a float represents a measurement taken with a certain precision, then it is 
simply *not the case* that 1.0000^^xs:float == 1^^xs:decimal.  They really are 
not the same.

It is true that the RIF decision was motivated much more by the need to comply 
with our existing implementation base, however that base is itself grounded in 
very real science and engineering, and very real and practical understanding of 
the mathematical properties of numbers.


-Chris


Sandro Hawke wrote:
> 
> My take on this: RIF justifies the choice of making xs:float and
> xs:decimal disjoint on the basis that this is needed in order for
> implementations of RIF to be based on existing implementation of xpath
> operators. The consequences of this choice for OWL go beyond simply
> making the types disjoint but bring addition constraints on types of
> facet values and additional complexity due to the possibility of
> implementation dependent results for the numeric operators. The
> adoption of xpath operators brings forward a number of issues that seem
> inadequately considered and this choice may turn out to be unworkable,
> in practice, even for RIF.
> 
> In order for OWL to be precisely defined we need to base our
> specification on the mathematical properties of numbers, not the
> properties of implementations.

-- 
Dr. Christopher A. Welty                    IBM Watson Research Center
+1.914.784.7055                             19 Skyline Dr.
cawelty@gmail.com                           Hawthorne, NY 10532
http://www.research.ibm.com/people/w/welty
Received on Wednesday, 18 February 2009 04:06:22 GMT

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