[QUANTITY] doc availability

[Jonathan McDowell]

Pierre,
 I'm sorry, the doc numbering problem is my fault. 
We originally had the doc as 0.5 and the day we were putting
it out there was a discussion about IVOA version numbering
which led me to rename it as 0.2 on the IVOA site, but I forgot
to renumber it on my own site.
 The document you have is, within a few minor improvements of
language, the same one as version 0.21 on my own site
 http://hea-www.harvard.edu/~jcm/vo/docs

 Let's concentrate on trying to get this document self-consistent
now. I'm not so concerned with the XMLSpy stuff at this point,
but we need to make sure that in the Q doc the UML, the English description
and the XML serialization are all consistent with each other.
As a second step we need to split the English description into a
pure English-for-astronomers bit and a computer-science-class-description
bit.
 Finally we need to list the pieces that are controversial even within
the Q paradigm: should BasicQ have errors, should it be called AtomicQ, etc.

 With all respect to Martin, I am not so worried about the bigger question
of whether Q is the right model to be doing. We should do other models
too, along the lines Martin suggests, and perhaps they will turn out
more useful in the end. I don't think we can settle that argument in advance.

 As far as the issue of a serialization goes, we must recognize that 
the serialization is the key thing we need if the rest of the VO is to
do anything with this model. Yes, there will be alternate serializations
(pure XML, VOTable etc) but only a small number and we must write them
down, not just infer them from the model, or we can't interoperate.

 The Latex source for the document is at qty.tex on my site;
anyone who wants to have a whack at improving the document, feel
free to do so or to send your edits to me or the list.

  Jonathan