[om] MathML draft Notes available for review

sal at dcs.st-and.ac.uk sal at dcs.st-and.ac.uk
Thu Jul 31 10:10:17 CEST 2003

> > 
> > the point I was making was that OpenMath must specify a unit
> > correctly and precisely. Currently for example, the pint is specified
> > as
> > 
> > "This symbol represents the measure of one pint. This is the standard
> > imperial measure for volume."
> Right - this sort of thing certainly needs to be fixed - it's become my 
> vacation project.
> > This might (incorrectly) be confused with the US pint (where in fact
> > there are two; liquid and dry). Also as stan was saying, these things
> > seem to have a habit of changing values depending on the date. Currently
> > in the units directories we say nothing about the dates of these
> > quantities.
> Um - good point. I'm not sure there's much we can do about this formally 
> other than through CD versions, but we could certainly ad text in 
> CDDescription.

Most non-metric units are thankfully defined in terms of metric ones these 
days (although I'm not sure who does this defining). Hopefully we could define

<oms symbol="imperial-pint" cd="units"> 

 by reference to a specific, dated, document that defines the imperial pint to 
be a specific number of litres.

Using this to its full exactness might require phrasebooks to, for instance, 
notice that a unit came from an old standard and apply a conversion factor (1 
+ epsilon, for pretty small epsilon) before using it.

There is a design question about whether we want to make a "default" choice of 
pint, ounce, and so on, which people will sometimes get wrong, or insist on 
people specifying "US dry pint" or "Troy ounce" every time, which will annoy 

Can one pose the riddle about a pound of feathers and a pound of Gold in 


Steve Linton	School of Computer Science  &
      Centre for Interdisciplinary Research in Computational Algebra
	     University of St Andrews 	 Tel   +44 (1334) 463269
http://www.dcs.st-and.ac.uk/~sal	 Fax   +44 (1334) 463278   

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