RDF vs. relational databases

I'm a newbie to RDF and have been facing a fundamental question as read 
more about RDF. RDF positions itself away from plain XML 
representations of data saying XML suited for representing data with 
containment hierarchies, and where "order" is important, whereas RDF 
has a flatter structure, represents only references among different 
entities. That sounds just like what a relational database is supposed 
to do, and those are critieria when deciding whether to used an XML DB 
or a relational DB to store your data. 
  Where does RDF fit in, and how does it compare to relational databases. 
I keep hearing that databases are not good for "semi-structured" data, 
but am not yet able to understand how RDF addresses that. Mozilla for 
example uses RDF for very structured (table of content) data. 
  What would be points of comparison where RDF is better suited to store 
and query my data? 
  Revi S. 




 		
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