[QUANTITY] Needs Coverage and Quality meta-data? (Was: Re: [QUANTITY] Plea for pragmatism)

[Brian Thomas]

On Wednesday 29 October 2003 08:43 am, David Berry wrote:
> I was thinking of COVERAGE and COMPLETENESS as a components of the
> OBSERVATION rather than the QUANTITY. You may want to use a QUANTITY to
> define the coverage. For instance, the spectral coverage of an observation
> could be specified by a 1D QUANTITY holding a bandpass.

	I agree with this design decision as well. The quantity model should be as
	spare, and reusable, as possible. As not all things need "coverage" (which I 
	understand as a sophisticated ensemble of min/max ranges on important
	astrophysical quantities), so it isnt needed by the quantity model.

	Perhaps a compromise is to allow some limited "range" meta-data in the 
	quantity which is reused at the higher component level for both coverage and
	completeness purposes.
	
> > QUALITY - gives a set of flags and/or enumerated values for each value in
> > the DATA component.
>
> This is a very complex information, very diffucult to attribute, which can
> evolve with time, depend on the subject studied...
> One data set unusable for a certain study, can be perfect (if not better)
> for another one.
> 
> Again, this is not suppose to characterise the overall usefullnes of the
> observation for some purpose, but just simply to assign specified flags to
> individual data values (e.g. "this value is saturated", "this value
> is vignetted", etc ). Characterising the usefullness of the whole
> observation would not be the task of a QUANTITY.

	I also agree again with David. The quantity should have a 'hook' for finding
	whatever "quality" flags the user/group defined at some higher level (like
	"component" or "observation"), but nothing more than that.
	I do believe this is the approach of most in the quantity community right now.

		-b.t.