Spectra DM for theoretical spectra? (fwd)

[Carlos Rodrigo Blanco]

>> The Spectra datamodel is perfect for most of the issues, but the 
>> characterization in SimDB
>> provides a better description of what the theoretical spectra is.
>> 
> Dear Miguel,
> 
> May I ask you what is missing in the SpectrumDM?
> What is SimDB offering extra, specific to spectra?

The main point, as I see it, is that the SpectrumDM is designed having observed 
spectra in mind, no theoretical ones.

The model contains everything that is necesary to describe the content of a 
spectrum (the wavelength, flux and all that, and this is the same for observed 
and theoretical ones) but nothing of what is needed to __characterize__ a 
theoretical spectrum.

For instance, a theoretical spectra is usually characterized giving, at least:

- the code used to synthetize it.
- the effective temperature of the star
- the gravity (logg) of the star
- the metallicity of the star

(and sometimes some other parameters)

And, in the spectrum data model there is no utype for those properties.

Making a long history short, if two different developers make two different 
services with theoretical spectra and one chooses "Meta" for the parameter 
containing the value for the metallicity and the other chooses "Z" for the same 
parameter, a client/application does not have a way to know that both refer to 
the same concept (and UCD's are not enough for this)

By the way, I think that SimDB doesn't solve that problem either, am I right?

I think that the spectrum data model should contain a section for 
characterization of theoretical data providing utypes for, at least, a minimum 
set of parameters associated to theoretical spectra.

The fact is that SSAP/SpectrumDM was done for observed spectra, it considers a 
lot of details about them, etc but it included theoretical spectra just as a 
use case in an appendix.

If it is going to be mandatory to use the same schema for theoretical spectra 
and it is expected that we do it (let's say) for ever, a little amount of time 
should be dedicated to fill the holes in the protocol/data model when it refers 
to theoretical spectra.

Carlos