Char DM and Sim DM: a use case

[glemson]

Hi Francois
We do need to understand characterisation better, hopefully in a way that 
defines the common concepts in the different approaches and allows us to see 
how the sppecific models derive from this. I made an attempt at starting 
this discussion in a DM session in last year's interop in Beijing, and would 
be interested in persuing this further. 

Cheers 

Gerard 

PS
This is what I hope to discuss with you tomorrow while I am still in 
Strasbourg, and what I have been discussing with Andreas in the train to 
yesterday. 

Francois Bonnarel writes: 

> Dear all, 
> 
>     As I was looking to the SIM data model, I was asked about the characterisation
> of some specific derived  data coming out of the Horizon simulation. I am
> speaking of these "maps" (either cubes or images) where the observable is a
> physical quantity (density, temperature, metalicity, etc ....). These data look 
> much closer to observational images and cubes than let's say ... snapshots of
> particules. But indeed the physical quantity playing the role of Observable is
> definetly a "property" in the sense of SIM DM, as far as I understand. 
>  
>      Presently the characterization class of Sim DM related to individual
> properties and gathering some figures such as nominal value, min, max,
> mean value, stdv is actually not inferred from the IVOA char DM. The
> statistical moments needed by Sim DM are not currently present in Char
> DM. But I am wondering if in the long term it could not be a problem for
> IVOA to have this kind of discrepancy between two classes sharing the
> same name and playing very similar roles. The use case I adressed above:
> "Metallicity-kind maps" typically belongs to the two worlds.  
> 
> As we, in the "Observation subgroup" of the DM WG are trying to upgrade 
> Characterisation data model in the direction of a fine grain description
> with correct definitions and as SimDM is not yet recommended I am wondering
> if it would not be possible to work on an harmonization .... What do you think ? 
> 
> Cheers
> François 
> 
> =====================================================================
> Francois   Bonnarel               Observatoire Astronomique de Strasbourg
> CDS (Centre de donnees          11, rue de l'Universite
> astronomiques de Strasbourg)    F--67000 Strasbourg (France) 
> 
> Tel: +33-(0)3 90 24 24 11       WWW: http://cdsweb.u-strasbg.fr/people/fb.html
> Fax: +33-(0)3 90 24 24 25       E-mail: bonnarel at astro.u-strasbg.fr
> ---------------------------------------------------------------------