SED data model v0.92

[Pepi Fabbiano]

> 1) Ed Shaya wrote:
> 
> > Hopefully, it is rare that one only has upper limit info.  The 
> > observers certainly should provide the measured value even if it is 
> > below the noise.  There is non-zero information in that value.
> 
> Well, although having only upper limits may seem pitiful, a number of 
> sound scientific results have been drawn in the past from 
> undetectablilty results. Upper limits are really a result for SEDs, and 
> used as such by astronomers. Since they are used, they are published and 
> they will go  in the  VO...
>  I just wanted to comment that a value *measured* cannot be *below* the 
> noise. Only the noise level is meaningfull in this case (the text notes, 
> and this is customary indeed, that authors usually "choose to render 
> measurements as upper limits if the flux value is less than some 
> multiple (e.g. 3) of the lower error" (note: shouldn't  be *Upper* 
> error? ) ). The risk would be, if any *measured* value is set, that is 
> is taken at face value, when only the noise level has sense. Could you 
> use some kind of blanking value for the measured value in this? (or is 
> there a general concept of upper limit that would go in the 
> Quantity::Accuracy data model?)

As someone who has written many papers using both detections and a significant 
number of upper limits, I entirely agree with the above comment.
 
> 2) in http://hea-www.harvard.edu/~jcm/vo/docs/spec.html, Errors are 
> OPTIONAL?? Errors are part of any measurement, and should be enforced by 
> the data model. Or is there provision for a sort of common error for all 
> measurements? Because a measurement without errorbars should simply not 
> exist  (but the reverse may exist, see above)!
> 

true 

> 3) http://hea-www.harvard.edu/~jcm/vo/docs/spec.html use  non standard  
> old 'ergs'  (cgs) units... All documents produced in the 21st Century 
> should promote MKSA units, and conversion to the dear cgs units of our 
> grandfathers should be implicit and computer-assisted... ;^)
>

I like cgs....
 
> Best,
> 
> Gilles

Cheers. -pepi


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