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Re: ISSUE-126 (Revisit Datatypes): A new proposal for the real <-> float <-> double conundrum

From: Dave Peterson <davep@iit.edu>
Date: Mon, 7 Jul 2008 16:21:32 -0400
Message-Id: <a06240818c497fcf40aba@[192.168.1.100]>
To: paul@sparrow-hawk.org, Alan Ruttenberg <alanruttenberg@gmail.com>
Cc: Rob Shearer <rob.shearer@comlab.ox.ac.uk>, public-webont-comments@w3.org, public-owl-wg@w3.org, www-xml-schema-comments@w3.org

At 10:38 AM -0600 2008-07-07, Paul "Sparrow Hawk" Biron wrote:
>Alan Ruttenberg wrote:
>>
>>I'm sorry for the overgeneralization and didn't mean to insult. 
>>It's just that as much as I think about it, I can't understand the 
>>idea that the value space of floats and the value space of decimal 
>>are disjoint. Fundamentally these represent some of the same real 
>>numbers and this isn't reflected in the spec. In addition, many 
>>numbers that can be finitely expressed and be calculated with find 
>>no place in *any* of the value spaces, e.g. 1/3. It is this sense 
>>of "mathematical" that I was referring to.
>
>The best explanation that I know of was written by Mark Reinhold, a 
>member of the original schema WG (...and, if memory serves me, was a 
>member of the team that wrote the Java floating-point spec).
>
>During the development of the Schema 1.0 (i.e., a few years before 
>we went to Rec) we had MANY discussions about the numeric types, and 
>especially about float and double.  As part of that discussion, Mark 
>wrote a note entitled "Floating-point datatypes are not real 
>datatypes" [1] that goes into great detail on this point.  It also 
>serves as a good entry point to the archives for the discussions the 
>WG had on these issues.

Thanks, Paul, for the history.  That discussion happened during a 9-month
period when I had to be away from Schema, so I wasn't really aware of it.

Interesting to note that the whole discussion of a parent for decimal,
float, and double (and even precisionDecimal) was reopened and discussed
during the early XSD 1.1 development, and again rejected (with and without
including precisionDecimal).  Apparently for much the same reasons.
-- 
Dave Peterson
SGMLWorks!

davep@iit.edu
Received on Monday, 7 July 2008 22:19:27 GMT

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