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From: Jonathan H Lundquist (jhl_at_[hidden])
Date: 2001-10-05 10:49:38

> From: "Eric Ford" <eford_at_[hidden]>

>> 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.

I think they have to be more than pure numbers, they're units of
measure in that bins can be converted to cartons, etc. But the
conversion factors do depend on the qualifiers.

>> 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.

We're converting to some fictional unit of volume, usually from another
unit of volume. However, we also have to convert from units of weight
to units of volume. A given number of lbs. of apples is a known number
of carton equivalents (approximated).

>> 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.

I meant dimensions, in loose english usage <g>. Perhaps I meant layers.
Since my original post there have been some posts about qualifiers/tags.
At the time I wrote, I thought most of the discussion treated what is
now being called tags as analagous to user defined units of measure.

I think the least which is needed are SI units, user defined units, and
tags. I also think tags have to be able to express what is and is not
fungible.