Re: danger of null value for summary attribute [Re: fear of "invisible metadata"]

I was going to talk about <summary> again but in the course of
composing this email I decided I'm pretty happy with what
table@summary and table/caption offer today:

<table summary="The columns
indicate sales in different regions and the rows indicate the months of
the year. The last row and last column show a total for the month or
region.">
<caption>Sales of widgets for the
financial year 2005-2006</caption>
...
</table>

Personally I would omit @summary in favour of brevity; trusting in
screen readers and their users to cope with the table structure (using
good thead/th elements to help with that naturally). I would sometimes
use <summary> for additional verbose description - which I feel is
appropriate in a <caption> - but I've survived this many years without
and I can't say it has caused me any grief.