From: Bijan Parsia <bparsia@cs.manchester.ac.uk>

Date: Wed, 18 Feb 2009 07:28:21 +0000

Cc: Chris Welty <cawelty@gmail.com>, Sandro Hawke <sandro@w3.org>, public-rif-wg@w3.org, Boris Motik <boris.motik@comlab.ox.ac.uk>, W3C OWL Working Group <public-owl-wg@w3.org>

Message-Id: <A40B8BE6-CB4F-4061-B5CB-CC73366D7386@cs.manchester.ac.uk>

To: Alan Ruttenberg <alanruttenberg@gmail.com>

Date: Wed, 18 Feb 2009 07:28:21 +0000

Cc: Chris Welty <cawelty@gmail.com>, Sandro Hawke <sandro@w3.org>, public-rif-wg@w3.org, Boris Motik <boris.motik@comlab.ox.ac.uk>, W3C OWL Working Group <public-owl-wg@w3.org>

Message-Id: <A40B8BE6-CB4F-4061-B5CB-CC73366D7386@cs.manchester.ac.uk>

To: Alan Ruttenberg <alanruttenberg@gmail.com>

On 18 Feb 2009, at 04:45, Alan Ruttenberg wrote: [snip] > So I must respectfully disagree with your assessment here. While there > very well may be *some* engineers and scientists that think of > floating point numbers in the way you suggest, there is not a single > way in which floating point numbers are used nor a single way in which > decimal numbers are used. The representation issue you mention is not > unique to floating point numbers, either in their specification, or in > their use. I remain of the opinion that the proper way to specify > machine representations of numbers is to define their behavior in > terms of their mathematical properties. [snip] And there is not an univocal structure that underlies "float". There are many possible mathematical structures. One of them entails that decimals are disjoint from floats. Another does not. (I have to do some interpretation to figure out what you mean by "specify machine representations of numbers...". I presume you mean that we should define the number system of OWL via standard mathematical apparatus (we do) such that they align with common mathematical connotation of the natural language terms (for which either disjointness or non-disjointness is justifiable). There is no univocal set of mathematical properties associated with the term "float" even up to reasonable isomorphism. So there is no "given" to adjudicate which mathematical structure we select. That is, you are *not* on the mathematical or philosophical high ground here, and I would appreciate it if you would stop writing as if you were.) It is perfectly proper to appeal to all sorts of considerations to justify the choice of mathematical properties we want of our datatype system including mathematical well-behavedness, intuitive appeal, usability, implementability, and alignment with other efforts. AFAICT, the considerations overwhelmingly favor disjointness. The main reason we went *off* disjointness was a rather tendentious argument about usability, a proven wrong argument about implementability, and fatigue. Implementability is firmly on the side of disjointness, the usability argument is further undermined by the usability costs of diverging from RIF (and standard interpretations of XML Schema), and I have a second wind :) Finally, I think it would be helpful at this stage to do some work to gauge the opinion/mood of the OWL WG. Given that the initial champion of disjointness has changed their mind in light of implementation experience (hence, new information), then, unless there are actual, new technical arguments in the offing, we should get a sense of whether there is consensus to continue with disjointness. If not, then we should see if there's "more" consensus to change. Cheers, Bijan. P.S. You may want to read Carnap's "Empiricism, Semantics, and Ontology" and Benacerraf's "What number's cannot be" -- just to pick two classic works that would, I hope, help dispel your confusions.Received on Wednesday, 18 February 2009 07:28:58 GMT

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