SED data model v0.92

[Ed Shaya]

> 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...

Let me rephrase my first sentence:
Hopefully, it is rare that one only has the upper lmit  but no info on 
the actual readout or measured value of the upper limit point.
So, we agree that upper limits are important scientifically. 

> I just wanted to comment that a value *measured* cannot be *below* the 
> noise. Only the noise level is meaningfull in this case

No!  Even a negative measurement on a property that is non-negative is 
scientifically meaningful.  See below.

> (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? ) ). 

You want the lower error bar to reach from the upper limit to the x-axis.

> 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?)
>
All I need say here is that if 4 independent experiments come up  with  
0.9 sigma  detections of  some measurement that it would be awful  if 
they each  published  only the upper limits of the value.
The possibility that some moron may not look at the quoted noise levels 
before coming to some silly conclusion on a measurment does not 
compensate for missing out on  potentially important real discoveries 
that properly archived data makes possible.

>
>
> 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... ;^)
>
> Best,
>
> Gilles
>