SED Data Model: Questions and Comments

[Pierre Didelon]

Gilles DUVERT wrote:

> Hi,
> 
> DM is not just the sum of its parts. One has to make choices. The need 
> is to insure data QUALITY and MAINTAINABILITY. Keep things simple. DM 
> should describe the physics of the data, that unite, not the habits of 
> the data producer, that divide.
> 
> So:
> Jonathan McDowell wrote:
> 
>> Reply to Igor's message of Jan 21:
>>
>>
>> Ideology:
>>
>> 2. No flux calibration.
>>
>> I'm still thinking about this one. In your case (shape right,
>> flux cal absent) one could just put a huge systematic error
>> bar on, but it would be better to have a special tag.
>>
>> The harder case is when the shape is globally wrong. This
>> is also common: no division by instrument sensitivity, so
>> that the shape is locally right (you can see lines and measure
>> redshifts) but globally wrong. So we need
>> a 'counts spectrum' case too.
>>  
>>
> A measure is a value and an error. 
counts are measurements and can have errors
> If there is no flux calibration, the 
> measurement does not exist, 
?
even before counts volt or amper at amplifiers stage exists!

>and a data model shall not be concerned by 
> this.
Your opinion!
If local shape can be of some interest to some people
why excluding it a priori?
And normalizing the spectra give a way to handle data like in way 1!
> DO NOT PERMIT TO WRONG OR UNRELIABLE DATA TO BE OUT IN THE VO!!!

IMO Even with a good model/protocol/technical_tools but without a good policy
bad/wrong/unreliable data can be pushed in VO!

SY
-- 
Pierre 
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