RDF Containment for xul:tree

Hi all,

I'm sure I remember either Neil or Axel saying that RDF for generating tree containment had to use rdf:Seq/Bag/Alt, is this correct?  I really 
want to create a hierarchy from the following RDF without adding any additional containment assertions:


<rdf:Description rdf:about="urn:level_1" dc:title="Level 1"/>
	
<rdf:Description rdf:about="urn:level2"	dc:title="Level 2">
   <dc:related rdf:resource="urn:level_1"/>
</rdf:Description>

<rdf:Description rdf:about="urn:level3"	dc:title="Level 3">
   <dc:related rdf:resource="urn:level_2"/>
</rdf:Description>



Where the dc:related assertion indicates the parent it is a child of.

Any thoughts if this is even remotely possible?

Cheers,

N