
Call for Feedback
In his post "RDFa in Drupal 7: last call for feedback before alpha release," Stéphane Corlosquet says that the Drupal 7 team wants to make sure that the platform generates "at least somewhat correct" RDFa out of the box, since not everyone will go to the trouble of installing additional semantic web modules.
One thing he'd like feedback on is the RDF terms they've used, offered in this diagram of the "default semantics of the core data structure:"

To help put the structure into context, he's also set up a testing site containing a blog post with comments along with some randomly-generated pages. A tracker generates a simple sitemap with the RDFa data, as shown here:
Learning Opportunities

Why Should You Care?
If somehow you've missed all of the discussions of the semantic web, this technology is meant to help computers understand the context that humans get intuitively when they look at a page. The key is the metadata attached to the content, and one of the standards for adding this metadata is RDFa, which lets you embed the context into your HTML.
Even if you don't feel qualified to give feedback, take a look and see what's coming, and try to wrap your head around it. Doing so will better position you over the months and years to come so you can bring your own web presence into the semantic world.
If you do feel qualified, take a look. As Boris Mann put it in another blog post, "Drupal 7 will be one of the first CMS tools that incorporate semantic web 'stuff' out of the box by default. Thus, several 10s of 1000s of sites will suddenly 'light up' semantically once Drupal 7 is released later this year. Let's make sure the default mappings look good."