W3C home > Mailing lists > Public > w3c-rdfcore-wg@w3.org > November 2001

Re: Literals: lexical spaces and value spaces

From: Pat Hayes <phayes@ai.uwf.edu>
Date: Mon, 5 Nov 2001 20:31:00 -0600
Message-Id: <p05101033b80cfaf1d714@[65.212.118.166]>
To: Graham Klyne <Graham.Klyne@MIMEsweeper.com>
Cc: w3c-rdfcore-wg@w3.org
>My particular beef with XML schema datatypes concerns non-integral 
>numbers.  I think the starting point for this value space should be 
>the set of all rational numbers, since any number represented in and 
>manipulated directly by a computer must necessarily be rational 
>(**).  All fixed- and floating-point forms represent rational 
>values.  But (as I recall) XML schema datatypes define non-integral 
>number value spaces based on either fixed-point decimal character 
>representations or IEEE floating point reprersentations.  This means 
>that some simple, everyday values cannot be represented directly 
>using primitive XSD numeric datatypes (e.g. 1/3, or the exact 
>conversion factor for millimetres->inches: 10/254).  This isn't a 
>purely academic argument:  we found rational numbers to be useful in 
>CONNEG work, and they have been defined for CC/PP.
>
>[(**) OK, you could devise exotic schemes where this isn't the case, 
>but for practical purposes I still claim that rational numbers 
>underpin just about all use of numbers in computers.]

Well, pi to you, Sir.

Seriously, I think that while you might be right about all arithmetic 
*computations* in computers, there is still in a descriptive language 
like RDF the possibility of naming, and making assertions about, 
certain irrational numbers. There are lots of mechanical algebraic 
reasoners out there for example which know things like sin(pi/2)=1.

Pat

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Received on Monday, 5 November 2001 21:31:01 EST

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