Re: SIunits and quantity library concerns

From: Eric Ford (eford_at_[hidden])
Date: 2001-10-04 21:43:23

> Quantities can be measured in bins, cartons, bags, etc., all of
which are
> user-defined units of measure.  

These can all be considered pure numbers.  You're counting something.  
You could think of this in terms of qualified units as a number: a
pure number qualified by what you're counting (_of_bins or _of_bags)
and a second qualification for what's in them (_of_bins_of_apples or
_of_bags_of_oranges).  In these cases I beleive you're more interested
in strong typeing for pure numbers than you are in a unit library.

> The only way to total them is by conversion to
> some
> common unit of measure, which the industry calls
'carton-equivalents'.  The
> conversion factors are subject to change from time to time.

You have to decide how you're converting.  You may decide you want to
measure weight in units of weight of one carton of apples.  Or you may
choose to use volumes instead.  You could define carton as a unit of
volume.  Then it could fit into the framework of SIunits.  You still
might want might want to add a qualifier to make something like
carton_of_apples, which presently is not possible with SIunits.

> Just thought I'd try to throw in a little real-world discussion.  I
think
> there
> are more dimensions to my particular problem than have been
discussed so
> far.

Do you really mean dimensions here?  Or just "it's more complicated"? 
If the former, please try to identify some dimensions other than
currency which are not possible in the framework of SIunits.

E