Spectra DM for theoretical spectra?

[Rick Wagner]

Hi Miguel,

> After the last interop I had find confusing how to represent a  
> theoretical spectra in the VO.
> Most of my problem is related with the characterization/description  
> about how the spectra has been
> obtained. It is a very important issue for theoretical spectra,  
> specially if it is going to be used as
> input in any workflow (e.j. stellar SED used as input for  
> photoionization).
>
> 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.
>
> I had heard in the interop, that if there is a DM of any quantity  
> (like spectra) it must be used
> this DM, but in the case of theoretical spectra I find it  
> incomplete (there is no place where I
> can said how the model has been computed and its inputs, that is  
> fundamental to
> understand what is modeled...).
>
> Is there any way to take the best of both DM? How?
> It is spectra DM mandatory for theoretical spectra or may I make  
> use of SimDB there?

This exact topic came up in a discussion about characterization  
between Gerard, Pat Dowler, Mireille Louys and myself. Briefly, (from  
my memory) the consensus we reached was that some theory data may  
need to be presented using both models; but, which model to use would  
also depend on the data was being accessed.

Some more information...

For clarity, I am going to use the term "synthetic observations" to  
refer to images and spectra generated from theory data or models.  
Another common term is "virtual telescope", but I worry about this  
phrase causing confusion with the more fundamental expression  
"virtual observatory".

Currently, the simulation data model has two concrete classes of  
Protocols (i.e., software): Simulators; and PostProcessor. Each of  
these can be used (with a set of ParameterSettings) to create an  
instance of a Simulation or PostProcessing, respectively. The  
PostProcessor class is very generic, and is intended to describe a  
large range of possible analysis tools, such as halo finding,  
extractions or projections.

Now, for the exact reasons you stated above, we may wish to add  
another type of Experiment, SyntheticObservation. The results of this  
would not be a Snapshot, but rather an SyntheticImage or  
SyntheticSpectra class, that could be linked to an instance based on  
the Spectral Data Model, or a future Image Data Model.

 From here, we describe from the theory perspective, how and why the  
data was created, and what we find interesting about. Also, if we  
wish to use a service type like SSA or SIA, we have the information  
we need, plus a means to add theory specific metadata.

Please, do not take this as the result of any kind of decision. This  
is just my memory of another conversation around a white board.

For now, the decision to be made is whether not we need these classes  
for our initial data model. Or, can we wait, and add them later. My  
preference is that we wait, and extend the model in a later version.  
But, this is a very important topic, and I'm glad you brought it up.

Ciao,
Rick

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Rick Wagner, Graduate Student Researcher
San Diego Supercomputer Center
9500 Gilman Drive
La Jolla, CA  92093-0505
Email:  rwagner at physics.ucsd.edu
WWW:    http://lca.ucsd.edu/projects/rpwagner
(858) 246-0745 Phone
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Creative algorithms are cool,
creative variable names are not.
--Rick Wagner
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