Just curious... what might be the compelling
reasons for not wanting to use XML? It doesn't
seem like you're objecting to the additional bulk in the
data, since some of your considered choices were potentially
bulkier; and (speaking as one who had to do basic SGML data
hacking
years ago, before modules) it's not as if XML tags are all
that tough or unwieldy for this sort of usage.
If/when you get around making this data portable/sharable -- trust
me, there are many who could find untold uses for it, if
you're willing to make it available -- you'll really want to
have it in XML anyway, so why not just do it that way now?