[QUANTITY] Why quantities always have errors

[Brian Thomas]

On Tuesday 18 November 2003 11:29 am, Martin and Brian wrote:
> > I think you are making the point that where there is no error with a
> > value, we should make it clear whether it is because we don't know the
> > error, or that there shouldn't be one.  I believe this discrimination
> > sould be in given in the 'type', as (1) it shows much more readily when
> > an error is relevent or not, and (2) it 'forces' the user of the type to
> > consider the error, rather than habitually setting it to 'None'.
>
>         Yes, agree, this is my point of view, and why I want "error" (or
>         actually, I'd call it "accuracy") on all quantities.

	Opps, I need to modify my agreement here. I think this makes sense
	(puting/connecting value with data type) when you have something like 
	"string" data type, which is always of a particular accuracy ("exact, no error"). 
	Not sure thats right for the numbers or not. Recall that some errors are "universial" 
	and apply to all values in the quantity (such as for a systematic error) but others
	apply directly on a value by value basis. Since the data type is a "universal"
	itself (all values have the same type), you have to be carefull for specifiying 
	accuracy there when numbers are involved.

	Regards,


	-b.t.

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  * Dr. Brian Thomas 

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  * Goddard Space Flight Center NASA

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