Spectral DM document update

[Doug Tody]

On Mon, 9 Oct 2006, Jonathan McDowell wrote:

> I've incorporated the recommendations from Moscow
> into the Spectrum document; it's at
> http://hea-www.harvard.edu/~jcm/vo/docs/spec98/spec98d.pdf
> There have been no changes to the list of UTYPEs but I have
> added mandatory/recommended/optional markers, and altered the
> FITS part following comments from STScI.

> I have not yet addressed the issue of the XML schema serialization
> of the data segment: the two alternate versions include a simple
> XML <Point>.... </Point> which is very verbose, and a more compact
> attribute-laden Point which was developed following Lazlo's example
> in the JHU service. However Lazlo himself suggested that we replace
> this with arrays like <Flux>1.2 1.3 1.4 ... </Flux> where all data
> point attributes are in separate arrays, instead of having
> Point No. 1 (flux, err, spco, ...) then Point No. 2 (flux, err, spco...)
> etc. I didn't get much feedback in Moscow about whether this was
> considered by others to be a good idea, since the email discussion
> got sidetracked onto the format-specifying issue that Lazlo raised
> in the same email.

This approach would make sense, as not only is it more efficient
for large spectral arrays of several thousand points, it is more
consistent with the other serializations, which are also array-based.
Data handling and transformations between formats would thus be
more straightforward.

 	- Doug