Revised ImageDM-ObsCore architecture

[Louys Mireille]

Hi all,
Le 14/11/2013 04:48, CresitelloDittmar, Mark a écrit :
> Doug,
>
> Thanks for the input..
> The "ObsCore" class of the right hand side corresponds to the Observation
> class of the ObsCore model document.  Future versions of the diagram will
> restore that name.  The left hand side (ObservationDM) is the Observation
> model used by Spectral, and presumably ImageDM.  The goal of the diagram
> is to show exactly what we need outside of ObsCore to support those 
> models.
> Explicitly stating the linkage.
>
> The best description of ObsCore is that it should be a 'view' of the 
> larger
> Observation model which serves ObsTap... so while the diagram may be
> ugly, I think it shows the relationships and provides all the 
> information needed
> to inform any request to modify the Observation model.
>
I agree with this way of expressing the relationship.
It clearly shows the richer side , on the left with the Observation DM 
package, and the excerpt or view on the right side.
This is indeed more tricky , because ObsCore uses some parts only of the 
Characterisation DM , and  SpectralDM uses a slightly different subset, 
and ImageDM might use another view or 'projection'of CharDM.

There are data model items from Curation , DataID , Spatial Resolution, 
etc... that are mandatory for the consistent description of an Image , 
and may be optional for an observation description or a spectrum.
This is the reason why I asked in Hawai'i that we should think of 
identifying clearly what is mandatory from what is optional for various 
use-cases.


>
> On Wed, Nov 13, 2013 at 8:10 PM, Douglas Tody <dtody at nrao.edu 
> <mailto:dtody at nrao.edu>> wrote:
>
>     Just to amplify on this point: in ObsTAP (ObsCore), it is permitted
>     for a record to describe either an Observation or a specific dataset
>     (data product).  So for example the Observation may be described,
>     and a
>     "package" can be downloaded containing multiple data products.  Or the
>     individual datasets (data products) may be exposed, linked by a common
>     obs_id.
>
>
> This seems to be echoing section 3.3.3 of the document.  If I 
> understand the doc
> and diagrams, the only way to get multiple individual data products 
> from the same
> observation is to have multiple instances, each having the same obs_id 
> value.
> Alternatively, one can have a tar file of products, but then the 
> observation details
> cannot be reported in detail for each product.
>
> I don't see an option for having 1 Observation with >1 Datasets fully 
> represented.
>
In the CTA data model we are trying to build , there is a need to bind 
several datasets together under one Observation .
the "1 to many" relation ship is needed. Therefore we need to extend the 
case where , in ObsCore , we had one data product for one Observation.

Thanks , Mireille.

-- 
Mireille Louys	, Maître de conférences
Centre de Données astrophysiques de  	Icube & Télécom Physique Strasbourg				Pôle API
Observatoire de Strasbourg 		300, boulevard Sébastien Brant
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