Blank nodes & classes

Hi all,

I have a question regarding blank nodes in RDFa, I don't know if the  
issue has been raised already and I apologize if it has. In the RDFa  
Primer I saw that you can create unnamed blank nodes using the 'rel'  
attribute as in the example:

<dl class="foaf:Person" about="#card" id="card">
....
  <dt>Address</dt>
  <dd rel="foaf:address">
   <span property="foaf:address_line_1">77 Massachusetts Ave.</ 
span><br />
     <span property="foaf:address_line_2">MIT Room 32-G524</span><br />
   <span property="foaf:city">Cambridge</span> MA 02139<br />
   <span property="foaf:country">USA</span>
  </dd>
....
</dl>

This works for predicates layered in an instance definition, do you  
plan having a similar principle for classes? I'd like to have:

<span class="foaf:Person" >
	some things about the person
</span>

to be considered as a blank node, currently in RDFa On Rails(http:// 
rdfa.rubyforge.org/) I generate blank node names this way:

<span class="foaf:Person" about="#BNode1">
	some things about the person
</span>

incrementing the number through the page generation, but this is  
ugly. The other solution is that I can just forbidden the use of  
classes if no uri or explicit blank node name is given.

Hope this does make some sense and look forward to get you point of  
view.

Best Regards!
---
Cédric Mesnage
PhD Student
cedric.mesnage@lu.unisi.ch
http://www.inf.unisi.ch/phd/mesnage/
http://myunderstanding.wordpress.com/