unit systems representations

[Henry Miller]

I've become interested in what I call representations for my application.  I have most of a spec in my company already, I'm wondering if the broader community of open source desktops is interested.  If there is already a spec that works I cannot find it, but I'll be happy if someone points it to me.

This is about what users see on the user interface.  I believe all "business logic" code should strictly work in metric units,  "the system" should have a layer (or possibly in the widget toolkit), to do this translation for the user.  Of course even when working in metric sometimes the correct unit to work with changes - if you are working with something very large or very small then using a meter will result in unacceptable floating point loss of precision, but this is still less dimensions to keep track of. (and hopefully avoid anything like a spaceship crashing because someone assumed the wrong units) 

The US of course hard our weird system. Astronomers typically use light year not the metric petametre. In every country historians will have do deal with whatever was used before the country adopted metric. There are also regions that have not really fully switched to metric resulting in measures like kg/acre being in use.

There are a lot of other complex factors that go into what to show.  Often it is easy/cheap to measure weight, but if the user wants to see volume the conversion gets complex - gravity isn't a constant, your material might not be pure, temperature, and pressure are sometimes vary enough to matter, some of those variables are easy to measure as well, but others require a lab.  

Even when the measure you want to show is simple, the exact unit can differ for different things - airplanes are measured in mm, while most other things that large are meters.  Or you might want to see 5meters, 3cm instead of 5.03m.

I am working on an idea that I think captures all the complexity of what measures really do in the real world.  Would the freedesk.org community be interested in making it into a standard. 

-- 
  Henry Miller
  hank at millerfarm.com