Re: Unit validation in spreadsheets

[Jody Goldberg <jody gnome org>]

On Sat, Mar 06, 2004 at 08:57:29PM -0800, Paul A. Steckler wrote:
> In our Excel prototype, rather than put the units in format strings, we 
> put them in annotations.  That's OK, but then the annotation 
> fields aren't available for other duty.  It would be better 
> to have separate fields for unit annotations.  Having units 
> in format strings might tend to clutter things.   
 
We'd probably tack them in via an extension to the value format

> Also, because some units are inferred, it might be confusing 
> to see units in the formats of some numbers, but not others.
> For finite formulas, our prototype only required unit annotations 
> at the leaf cells.  All other units are inferred.  The main 
> technical contribution that we made (IMO) was the technique 
> we devised for inferring units for formulas with circular 
> dependencies.  Does the system there now handle circularity?

We do handle circularity.  However, it's important to keep clear on
the distinction between user visible expressions and calculation
inside functions.  We'd need to handle those on a one off basis
somewhat.  So if someone wanted to add a metre to a litre via '+' we
could catch it, but SUM would take more work.

> I'd certainly like to participate in the design of a unit 
> inferencer; some of the others who worked on our Excel prototype 
> -might also want to do so.

Great.  The key will be in getting a coherent design.

> Myself, I'm probably unable to devote enough cycles to do 
> the bulk of the coding (although I can probably do bits of it).
> My hope is that someone in the Gnumeric community might be interested 
> enough to take that on.

I'd be interested in helping code it, but things are stretched
pretty thin.  Alot would depend on how intrusive the design changes
are.