Spectra DM for theoretical spectra?

[Gerard]

Hi Carlos

> 
> I think that there is a minimum set given by:
> 
> Teff: effective temperature of the star
> Logg: logarithm of the gravity
> Metallicity (for some authors this is the fraction of 
> elements heavier than Hidrogen and for other it is something 
> different, I can ask for a better definition to some real 
> astronomer :-)
> 
> Some models need more parameters, but this would be a nice 
> start (those are the ones that I use for most of the services 
> that I'm using).
> 
> In any case, I'm going to do a better list and I send it to you
> 
> Maybe other people need other parameters... for instance, 
> recently some people from a group in France emailed me asking 
> for a data model to describe their theoretical spectra in the 
> VO and they sent me some quite complicated examples of what 
> they were doing, I'll ask them too
> 
> (by the way, I would wish to keep this list simple, 
> containing only those parameters so important that "nothing 
> can be done without them", and then having the usual 
> discussion on how that list can be extended or not and if 
> something sofisticated is needed for the general case)
> 

All of this can be modelled in SimDB, using the SimDB:InputParameter and
SimDB:ParameterSetting classes.

In XML you could describe this somewhat like the following (and let's not
argue about the term <simulator> 
which you might prefer to be <model> or who knows what)

First you describe your simulation code (model code):

<simulator>
<name>My favorite stellar model</name>
...
<inputParameter>
<name>Teff</name>
<description>effective temperature of the star</description>
<label>Some term from a semantic vocabulary that allows one to indicate
physical concepts and observables.</label>
</inputParameter>

<inputParameter>
<name>Logg</name>
<description>logarithm of the gravity</description>
<label>Some other term from a semantic vocabulary that allows one to
indicate physical concepts and observables.</label>
</inputParameter>

<inputParameter>
<name>Metallicity</name>
<description>fraction of elements heavier than Hidrogen </description>
<label>Some other term from a semantic vocabulary that allows one to
indicate physical concepts and observables.</label>
</inputParameter>

</simulator>

This has to be defined only once, and now all runs (models?) can refer to
this code and list parameter settings:

<simulation>
  <simulator>My favorite stellar model</simulator>
  <parameterSetting>
    <parameter>Teff</parameter>
    <value>1234</value>
  </parameterSetting>
... 
</simulation>


Now one may argue that this is not as explicit as for example

<MyFavoriteModel>
<Teff>1234</Teff>
<Logg>1</Logg>
</MyFavoriteModel>


But that model ONLY works for MyFavoriteModel, whereas the SimDB version
works for all models that have input parameters.
Moreover, the simulation code itself is explicitly described in the model
itself.
I don't think this is very difficult?

It may be possible for a selected sub discipline to define an explicit set
of parameters for which "nothing 
can be done without them". Possbily stellar atmospheres, evolution. These
were actually singled out in last year's EuroVO DCA theory workshop and it
was suggested that they get together and try to define this kind of explicit
models.
There was interest amongst participating scientists to contribute to such an
effort. I can give names and email addresses if this is of interest.

But note that this group is not defined because they produce synthetic
spectra.
But because they use similar types of models (or SimDB:Protocols in
SimDB-speak). 

For example people producing galaxy spectra will have a different opinion
about what input parametesr they can not do without.




Gerard