ImageDM: what does extension mean?

[CresitelloDittmar, Mark]

On Fri, Oct 25, 2013 at 12:57 PM, Ray Plante <rplante at illinois.edu> wrote:

>
> My question is, what does it mean technically for ImageDM to "extend"
> ObsCore?
>
> One result we might expect is that the ImageDM would not be explicitly
> "re-defining" the ObsCore metadata and UTypes; rather it would point
> to the ObsCore document for its definition.  Is there more to it,
> though?  Is there something implied about the structure of UML models?
> How about serializations?  Should a client that is only ObsCore-aware
> be able to interpret the ObsCore portion of an ImageDM serialization?
> What does it mean for how we define the extension metadata?
>
>
In my opinion, this is the way to go.
The composite models (Image, Spectral) should 'refer' to the component
models.
They can include summary or semantic details, but should defer to the
original
for definition and detail.  This reduces the 'bloat' in models and these
small variations
we are struggling with due to migrations and 'simplifications'.

For the ObsCore extension, there are some details at the top level which
need to be resolved (see the 'Convergence' thread).  But this question
brings
up a good point w.r.t. serialization.  Serializations include the model
'prefix'.
For ObsCore serializations, this is 'obs'?, other models will have a
different
prefix.  Optimally, an ObsCore aware application should be able to ignore
the
prefix and recognize the content.  This would probably work, but only
because
it is a TOP level model.

This is similar to discussions which went on for lower level objects, where
the
practice of combining utype strings make it impossible for a generic
utility
to identify the axes (for example) within a model an plot them.

Mark
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