[SPECTRUM] Revised spectral data model

[Jonathan McDowell]

I've placed a copy of my ADASS poster at
http://hea-www.harvard.edu/~jcm/vo/papers/adass03.poster.ps
with a more easily printable text version 
http://hea-www.harvard.edu/~jcm/vo/papers/adass03.ps
This document reflects work by the CfA VO group in elaborating
the earlier spectral model suggestions, and I hope it
will serve as one reference point for our discussions on
spectra at Interop - this is likely to be centered in the
DAL working group session, which Doug Tody is leading.

  Jonathan McDowell