A Proposal for subject setting by @class

We've recently had a discussion about what to do when one wants to
publish a calendar event on a page without necessarily naming it.

The recommendation was:

<div class="cal:Vevent" rel="rdf:li">
...

or rel="foaf:topic"

(note that I'm using the @class notation though this issue has now been
reopened, so assume

the_attribute_that_shall_not_be_named="cal:Vevent"

where I say @class.)

I propose that, when a @class appears with a namespaced-value, there be
an implicit @about set for contained statements, exactly as if there
were a @rel. I suspect someone else has brought this up before, but I
can't seem to find it in the archive.

So, for example:

<div class="cal:Vevent">
  <span property="cal:dtstart">2007-07-07</span>
</div>

would yield:

_:div0 rdf:type cal:Vevent ;
       cal:dtstart "2007-07-07" .

This is a small but noticeable change, and it may invalidate some
existing markup (though unlikely, since most use case here involve using
an @about on the same @div, in which case the @about takes precedence.)

Thoughts, comments?

-Ben