[QUANTIT] Use-cases, role in larger scheme (Was: Re: [QUANTITY] Quantity "arguments")

[DIDELON Pierre]

> From Edward.J.Shaya.1 at gsfc.nasa.gov Mon Nov 17 17:05:49 2003
> Date: Mon, 17 Nov 2003 10:59:03 -0500
> From: Ed Shaya <Edward.J.Shaya.1 at gsfc.nasa.gov>
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> To: DIDELON Pierre <dide at discovery.saclay.cea.fr>
> CC: dsb at ast.man.ac.uk, dtody at nrao.edu, brian.thomas at gsfc.nasa.gov, dm at ivoa.net
> Subject: Re: [QUANTIT] Use-cases, role in larger scheme (Was: Re: [QUANTITY]
>     Quantity "arguments")
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> 
> 
> DIDELON Pierre wrote:
> 
> >just one more argument in favor of my favorite Quantity model (pat's one),
> >but let's try to be more complete and explicit.
> >
> >I prefer VERY SIMPLE object instead of complex ones, 
> >mainly considering a bottom-up approach, because :
> >  
> >
[SNIP]
> 
> Likewise, it is inappropriate to have a separate class for the quantity 
> with no error because it is unknown or so precisely measured that it is 
> zero, as in the case of knowing that there are exactly 2 planets closer 
> to the sun than Earth.  It is fair to say that there is a special class 
> for a number with units that the user sets as a parameter in a query or 
> a directive to an application, that *logically* has no error.  But, do 
> you really want this to be a direct subclass of Thing so that it is 
> totally unrelated ontologically to quantity?  Afterall, its main purpose 
> is to be directly compared with quantity objects.  In OWL the expedient 
> thing to do was to slightly broaden the definition of quantity by making 
> Error an optional property.  Then if you want to one can subclass these 
> into two, one with an Error required and one without.  And, of course 
> you can give these three classes totally different names, but the  
> principle remains the same.  But, it will remain that the thing with no 
> Error is a fairly rare beast because it absolutely can not take an 
> Error.  Perhaps a Range though.


I don't understand. I am lost.
Errors exist in Pat's model, it is agregate one level "above" in Measurement. 
Some measurements (or whaever name will be agreed on) will have errors and some not.
Why trying to forbidd the concept of number without error
if it can be introduce (for free) and claim as necessary by some people?
 

Pierre