Spectrum Data Model Implementation

[Doug Tody]

Hi Tamas -

On Mon, 7 Jun 2004, Tamas Budavari wrote:
> Those 3 columns are defined in the <Wavelength> tag, which in fact seems
> to be missing from the "simple" example. Thanks for pointing it out! This
> implementation was BTW following the IVOA twiki document
> 
> 	http://www.ivoa.net/internal/IVOA/IVOADMSpectraWP/spec.pdf
> 
> I think it's called something different in version 0.5 but still separate
> GROUP in VOTable terms.

The most recent version of the SSA data model I am aware of (V0.5) is the one
on the DAL wiki page from the Boston meeting, at

    http://www.ivoa.net/internal/IVOA/InterOpMay2004DAL/spec2.pdf
 
> Unfortunatelly, empty columns in the current data model (or class
> structure) can't be just omitted easily. If they were objects and not
> numbers, then we could make them nullable (or nilable). We may be able 
> to play some tricks here if really needed but in this prototype we kept
> everything even though didn't fill in all the fields.

So far as the *data model* is concerned the fields can generally be
omitted, or vector fields can be represented as scalars.  This is actually
a pretty important aspect of the SSA data model since dataset instances
will generally be much simpler then the full data model permits, with only
2-3 vector columns and many of the scalar parameters omitted or defaulted.
The interesting issue here is whether this flexibility in representation
can be implemented reasonably with XML Schema and WS.  Can we omit or
default defined elements, or extend the model with non-standard elements?

	- Doug

> 
> On Mon, 7 Jun 2004, Pierre Didelon wrote:
> 
> > 
> > 
> > Tamas Budavari wrote:
> > > I believe this is relevant for many people on the dm, dal, grid, apps and
> > > votable IVOA mailing lists, so I figured I'd send it to interop...
> > > 
> > > Following the proposal for the spectrum data model, we have completed a 
> > > first implementation of an XML Web Service that returns spectra in the 
> > > new VO (proposal) format. Please go to
> > > 
> > > 	http://www.voservices.net/SpectrumSchemaWs/
> > > 
> > > The links on the bottom of the page show you how our class gets serialized
> > > into different xml formats that might be simple or more complex depending
> > > on the content.  A VOTable version of them is also implemented for
> > > reference. 
> > Hi,
> > 
> > Concerning the simple spectra VOTAble serialisation,
> > you have only 5 FIELD definitions with 8 TD cells in each row.
> > comparing with XML, it seems that definitions of Wavelength, BinLow & BinHigh
> > are missing.
> > 
> > Fields without meaning full value (like Error, ErrorLow,ErrorHigh & Quality)
> > can't be omitted? Or given as PARAM in the header to specifiy default
> > or unknown values,
> > 
> > SY
> > 
> > 
> 
>