VOTable multi-dimensional arrays too restrictive

[Markus Demleitner]

Hi Gerard,

On Thu, Feb 18, 2021 at 12:45:25PM +0000, Gerard Lemson wrote:
> Not that I propose using it, but what are the reasons *against*
> going full XML and have something like <TD><A> ... </A></TD>, where
> the content of the <A></A> could be a bunch of <V></V>-s and each
> <V> could contain another <A></A>? Would keep it fully XML and
> maybe dissuade people from using it too much?

If TABLEDATA were all we have, that would be rather straightforward.
But it's not, and embedding such XML fragments in BINARY2 would suck,
in particular for floats and ints, where you'd suddenly see all of
TABLEDATA creep in.

But in the end for characters it's the same idea as SI (<A>), SO
(</A>) and ESC (which in XML is a bit more complex), so there nothing
wrong with it in principle.

> If some special syntax is chosen, would be acceptable for all array
> values inside VOTable cells, or only multi-dimensional ones?

Me, I'm really sure whatever we cook up here would only be activated
by some magic value in a FIELD's arraysize attribute.  Changing
anything in our other serialisation rules would quite certainly break
quite a bit of software that is actually being used.

Where, of course, I suspect we can't avoid breaking clients when the
arrays of variable-length arrays are actually used -- but the clients
would clearly say "I don't understand this arraysize" rather than
produce garbage.

         -- Markus