RE: Table Techniques - Summary

I would suggest that the presence of the <TH> element is a better indicator
of an author's decision about whether a table is a layout table or not. 

Assuming that we require that (a) all data tables have TH elements and (b)
layout tables do not have TH elements, I think that also requiring summary
on layout tables is an unnecessary requirement. The existence of TH (or lack
thereof) could just as easily be used for triggering user checks and
prompting the author to classify the table type. 

Defining table type based on the TH element also allows us to put forth a
clear and simple rule about the use of the summary attribute on layout
tables rather than suggest that they may or may not be used in certain ways
(null vs. absent) or on certain types of layout tables.

Also, if both the use of layout tables and the use of CSS are legitimate
strategies for adjusting layout, then it seems to me that these strategies
should have comparable mechanisms/requirements for including summary
information. Since the CSS approach (which is at least in theory preferable
to using tables for layout) does not include a mechanism for summarizing
layout, I see no reason to require the presence of the summary attribute on
layout tables.

-Ben