[QUANTITY] Why quantities always have errors

[Brian Thomas]

On Tuesday 18 November 2003 11:52 am, Martin Hill wrote:
> >       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.
>
> Gah I don't understand this, probably because we're using the same words
> for different things.  To me type=class/interface (so Flux, Co-ordinate,
> even Quantity if there is such a thing, are all types); are you using it
> for 'primitive types'?  Why is a data type universal?  is a 'value' not
> a quantity?

	My bad. By "universial" I mean that that meta-data applies to all 
	the values (e.g. if one values is "integer" then all the others are
	too). Sometimes, errors are "universial" (e.g. one piece of meta-data
	suffices to describe the error on all values, such as is the case with
	many systematic errors) but often, they are not, and you need one error
	for each value. 

	Thats all I meant to say. Hope that clearer.
	

	-b.t.


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  * Dr. Brian Thomas 

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