Spectrum data model

[Doug Tody]

Hi Mark -

On Wed, 13 Sep 2006, Mark Taylor wrote:
> I follow this but I still have a problem: the Dataset.DataModel and
> Access.Format are not sufficient to describe fully the format of a remote
> data file (which I would like to know, for instance, if I'm a client
> who has the SSAP query response and wants to know whether it's
> worthwhile retrieving the remote resource or whether it's unreadable
> to me).
>
> The reason is that there may be multiple different and incompatible
> serializations which share the same Data Model and MIME type.
> For instance, an instance of the Spectrum V1.0 DM could be encoded
> as application/fits either using the serialization suggested in
> Part 4 of the current Spectral DM document or as, say, a 1D FITS
> array, or any number of other FITS-based serializations I could
> dream up.  Possibly the intention is that the *only* legal serialization
> of Spectrum V1.0 into FITS is following the prescription in
> spec98c Part 4 (though I'm not sure that would be a good idea),
> but as far as I know that is not explicitly stated anywhere.
>
> Hence my request for an additional specification somewhere (in the
> SSAP response) which ties down the serialization more tightly.

Thanks, I see your point and you are correct that there could be multiple
FITS (for example) serializations of the same data model.  The file
format alone is not enough to describe this.  The intention was that for
Spectrum only the documented serializations would be used, but I agree
that we do not yet have a way yet to fully specify the serialization
and that this would be a useful thing to add.  (Perhaps something like
DataFormat to go along with DataModel; this would be different than the
file format specified in a MIME type level of granularity).

	- Doug