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Units (inches and centimetres, etc)

From: Graham Klyne <gk@ninebynine.org>
Date: Mon, 16 Jun 2003 15:25:27 +0100
Message-Id: <>
To: RDF interest group <www-rdf-interest@w3.org>

I find myself wondering if the proposals for unit conversions are slightly 
missing a deeper, more pervasive issue.

A statement to the effect that 1 inch is 2.54 centimetres I think has two 
important parts:

(a) a universally quantified assertion;  e.g. forall x, x inches is the 
same as f(x) centimetres, for some specified f.  This seems a bit like a 
"rule" to me.

(b) arithmetic relations:  the function 'f' alluded to above being defined 
in terms of common arithmetic operations.

(I observe that similar case not amenable to a simple conversion factor 
would be to express the equivalence of temperatures expressed in Fahrenheit 
or Celsius scales.)

To date, RDF has not standardized any form or arithmetic 
relationship.  Means to represent numerical values are relatively new, 
currently proposed by RDFcore.  CWM has built-in properties that correspond 
to arithmetic relationships [1].

This suggests to me that we don't really need anything new that isn't 
already being done.  There's a lot of activity devoted to the development 
of rules [2] [3].  It seems that there already exists a design for RDF 
properties dealing with relations based on arithmetic operations [1], 
though I could see a case for making that work a little more "forceful" -- 
e.g. by publication as a W3C Note, with a view to taking it to the 
recommendation track in future RDF working groups.


[1] http://www.w3.org/2000/10/swap/doc/CwmBuiltins.html (see math: predicates).

[2] http://lists.w3.org/Archives/Public/www-rdf-rules/

[3] http://www.daml.org/rules/

Graham Klyne
PGP: 0FAA 69FF C083 000B A2E9  A131 01B9 1C7A DBCA CB5E
Received on Monday, 16 June 2003 10:28:48 UTC

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