Revised ImageDM-ObsCore architecture

[CresitelloDittmar, Mark]

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.


On Wed, Nov 13, 2013 at 8:10 PM, Douglas Tody <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.


>  Or some combination of the two.  So there is a distinction
> between an observation and a dataset.  An observation may have multiple
> datasets.  An individual dataset has a type, a subtype, a calibration
> level, a size, and so on.  (it is also possible to have datasets that
> are not observations).  - Doug
>

I don't think there is a use case for a Dataset that is not associated with
an Observation..
The above is saying that Observation "has" 0+ Datasets.. rather than
Observation "is" a Dataset.
I see nothing in ObsCore to indicate the former.

Mark
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