[Cube/ImageDM] NDImageDataset Comments

[Louys Mireille]

Hi Mark,
Hi all,

I am trying to recap on the various diagrams you have produced . It is a 
huge amount of work , as said before which accomplishes a global 
adjustment of all the concepts worked out so far in the DM WG effort.
Please take my comments as constructive criticism only.

Here a few comments about the ND Image Dataset diagram:
Let me just reformulate what I have understood from the diagram, and how 
I can interprete it for an Image processing application  :

an NDImageDataset is a subclass of ObsDataset, and contains a set of 
PixelatedData, that I can reference by using the reference "data".
"data" could possibly be implemented as the pointeur to the ND-array of 
all the Voxels that are read in a FITS file when I load the file content 
in memory , for let say astrometric calibration , registration , 
regridding , etc.

As mentionned by FB and MCD , the composition is tricky here :
I would not expect an abstract class to be an element of Voxel ( here 
/AstroAxisCoordinate/) .
I guess , we have an easier way in composing directly the different 
'something'AxisCoordinate classes , for which we can specify the 
cardinality one by one .

I suppose that the ND array inside the PixelatedData will be read from a 
file.
Where is this file name stored in the model ?
If I look in DatasetOverview diagram , I can probably extrapolate the 
filename I am talking about from the DataID Class, but I think , it 
would be much simpler to use the Access class that was designed in ObsCore.

More in separate mails.
best regards , Mireille



  Le 30/04/2014 21:47, CresitelloDittmar, Mark a écrit :
> Francois,
>
>
> On Wed, Apr 30, 2014 at 1:32 PM, François Bonnarel 
> <francois.bonnarel at astro.unistra.fr 
> <mailto:francois.bonnarel at astro.unistra.fr>> wrote:
>
>     Hi all,
>        Hummm you got more answer on you other email on datatypes than
>     on this one.
>        Very nice diagrams again. The general changes for SparseData
>     and NDImage seem very good to me.
>
>
> Thanks.
......
>
> If we relate to earlier incarnations:
>   - pixelatedData == storage of ND data array.  The PixelCoordSys is 
> associated with this object because it contains the PixelFrame 
> descriptions for that array and their Transforms to the broader world 
> coordinate system(s).  Different data arrays may have different 
> transforms from their pixel coordinates to the same world coordinate 
> systems.  The AstroCoordSys definitions are valid for, and owned by 
> the Dataset as a whole, so it is associated with the ObsDataset.   It 
> may help to show that in this diagram.
>
>   - voxel == I am using 'voxel' to represent the fundamental ND volume 
> of coordinate space.  It has associated with it, the various 
> 'coordinates' of the volume in the ND space (pixelAxes, 
> independentAxes), and the 'observable' value AT that location 
> (dependentAxis).  I am not positive the composition relation is 
> correct here, but I think it is.
>    The actual values of the AstroAxisCoordinates may be defined 
> (generally would be), as a transform of the pixelAxisCoordinates (via 
> WCS info), and computed.  This is shown in the STCMod:Coordinates 
> diagram.  AstroAxisCoordinate is an extension of Coordinate, and has a 
> reference to the associated Frame which holds the Transform 
> information needed to compute the value. (STC: Overview)
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