Issue: Should the spec treat tables without explicit tbody's as non-conforming, or treat style rules that produce different results based on the existence of tbody elements to be non-conforming?


Current spec language: 
For a polyglot document, a table must  explicitly have a tbody element surrounding groups of tr  elements. HTML pasrsers insert the tbody element, but XML parsers do not, thus creating different DOMs.
Correct:
<table>
  <tbody>
    <tr>...

Incorrect:
<table>
  <tr>...


Notes:
Issue raised in mail sent by Sam Ruby[1]:
There are two ways to address this: treat tables without explicit tbody's as non-conforming, or treat style rules that produce different results based on the existence of tbody elements to be non-conforming.  As luck would have it, I had an opportunity to observe this exact discussion. DanC and PLH preferred it when tbody elements were included, TimBL preferred to not include tbody elements when they were not necessary.  I didn't express an opinion in that venue, but I will say that while I don't currently routinely use tbody elements, I do think it would be better approach if this document were to suggest that they were required.


[1] http://lists.w3.org/Archives/Public/public-html/2010Apr/0036.html