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RE: Where I am about floats, etc. - ISSUE-126

From: Boris Motik <boris.motik@comlab.ox.ac.uk>
Date: Mon, 7 Jul 2008 00:15:51 +0100
To: "'OWL Working Group WG'" <public-owl-wg@w3.org>
Message-ID: <000001c8dfbe$3c20c520$0200a8c0@wolf>

Hello,

I wholly support removal of xsd:float and xsd:double from OWL 2 and supporting the remaining numeric types as subsets of owl:real,
and even introducing owl:rational. I see no problems in supporting those in practice and their specification should be really easy.
If implementors want, they can always choose to support floats.

Regards,

	Boris

> -----Original Message-----
> From: public-owl-wg-request@w3.org [mailto:public-owl-wg-request@w3.org] On Behalf Of Bijan Parsia
> Sent: 06 July 2008 23:00
> To: OWL Working Group WG
> Subject: Where I am about floats, etc.
> 
> 
> I'm now inclined toward having two primitive built in datatypes
> string and some flavor of real. I'm pretty ok in allowing all of the
> types derived or derivable (using facets we permit) from them in the
> XSD scheme. (So, I'd definitely put in xsd:decimal, for example). Any
> additional ones need to be considered carefully and perhaps much
> later in the game. (Even something like anyURI would need a fair bit
> of attention. Alas :()
> 
> I think I'm specifically against including xsd:float and xsd:double
> as types at all at this stage, and even as our specing them out as
> optional. (We shouldn't forbid them; just be silent.)
> 
> It's pretty evident that there's a fairly wide set of views on float
> and double, including a set of varyingly negative ones (or rather,
> ones that would like to effectively eliminate them). Given that we've
> already had some thinko-s about them and their various
> characteristics, I don't think it's a good idea to try to meddle with
> them. (Note that we've had varying, absolutely confident reports on
> which bits were necessary (think of the discussion around NaN). I'm
> not confident that we can get good data on what's "really wanted"
> here esp. since some of the ramifications aren't obvious.) Tweaking
> their semantics somewhat randomly just seems like a very bad idea to
> me, and a waste of effort. I'd rather nail down the particulars of
> fewer types and get excellent, wide support for them. Working with
> implementors outside of the group on float and double support seems a
> better bet at this stage.
> 
> I recognize that this does not address some important use cases and
> makes OWL tougher for dealing with scientific data (in particular).
> But given that xsd1:float has some issues (e.g., 1 zero and only 1
> NaN), it might be better all aroudn to punt on it.
> 
> (A work around would be to have a named string user defined type. It
> wouldn't do syntax checking, but my understanding of the use case
> (and it's a recollection because email search sucks hard) is that the
> issue is transmission of data, not reasoning about it. Another work
> around would be to lobby implementors. Yet another workaround would
> be to use the corresponding integers. None of these are thrilling.
> However, if the use pattern is dump to a format and load into
> another, they may be tolerable.
> 
> For this use case, I'd be a bit leary of XSD1:float, given its
> quirks. I have no idea if scientific computing uses the various
> distinct NaNs in some fashion, but it wouldn't surprise me. It seems
> to be identified as important here: <http://math.nist.gov/
> javanumerics/reports/jgfnwg-01.html>. Signaling vs. non-signaling may
> be significant...I don't know.[1])
> 
> Cheers,
> Bijan.
> 
> P.S. This is a nice paper: http://hal.archives-ouvertes.fr/docs/
> 00/28/14/29/PDF/floating-point-article.pdf
> 
> [1]  I couldn't find a specific example, but <http://docs.sun.com/app/
> docs/doc/800-7895/6hos0aou4?a=view> sez:
> 
> """In IEEE 754, NaNs are often represented as floating-point numbers
> with the exponent emax + 1 and nonzero significands. Implementations
> are free to put system-dependent information into the significand.
> Thus there is not a unique NaN, but rather a whole family of NaNs.
> When a NaN and an ordinary floating-point number are combined, the
> result should be the same as the NaN operand. Thus if the result of a
> long computation is a NaN, the system-dependent information in the
> significand will be the information that was generated when the first
> NaN in the computation was generated. Actually, there is a caveat to
> the last statement. If both operands are NaNs, then the result will
> be one of those NaNs, but it might not be the NaN that was generated
> first."""
> 
> This suggests that picking a special NaN concept would limit the
> utility of transmitting scientific data via OWL.
Received on Sunday, 6 July 2008 23:17:28 UTC

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