summary attrib not forced in tables

i think everything must validate with tidy and W3C

Agree.

Why does for e.g. table not force a summary attibute?

Because it is optional according to http://www.w3.org/TR/html4/struct/tables.html#adef-summary

I thought Drupal does only produce valid XHTML and is using XHTML 1.0 Transition or higher.

Yes, Drupal uses XHTML 1.0 Transitional and it does not fully validate (www.drupal.org) as stated within the HTML. Anyway I successfully developed themes that are fully validated under the XHTML 1.0 Strict. OTOH, the new Garland theme is XHTML 1.0 Strict and fully validates.

I was told drupal core does not create valid code

It does.

"summary" with a helpfull value if they create a table in HTML

Yes it would, and there are more issues in the queue to make a more accessibility aware Drupal.

Note to myself: I wish a fully http://www.w3.org/WAI/ and http://www.w3.org/TR/WAI-WEBCONTENT/ Drupal 6.0

So now we're looking at Drupal 7 & WCAG 2.0, see http://www.w3.org/TR/WCAG20-TECHS/H73.html

We are now pretty much table free within Drupal core though. Not sure though what mechanisms within core affect summaries within tables though.

Might be good to raise this point here - http://groups.drupal.org/accessibility

Drupal Core 6 & 7 Validate xHTML Strict throughout I think. We're working on raising the bar too.

Looking at this issue I'm not sure that I am clear on the requested deliverable. If there is a table within Drupal that would benefit from the optional summary attribute then perhaps an issue should be filed against that module / theme.

As far as I can tell this issue can be closed.

Setting status to won't fix. The table summary attribute is optional in xhtml and wcag 2.0. If there is a particular table in Drupal which would benefit from the summary attribute an issue should be filed against that module / theme.