* source code:
 
   http://code.google.com/p/rdffederator/

* step:

  1.data download:
    
   drugbank:  http://download.bio2rdf.org/release/3/drugbank/  drugbank.nq.gz	19-Dec-2014 13:23	52M
   
   omim:      http://download.bio2rdf.org/release/3/omim/     omim.nq.gz	11-Nov-2014 03:50	124M	 

   pharmgkb:  http://download.bio2rdf.org/release/3/pharmgkb/

 2. ./generate_void.sh ../data/drugbank.nq drugbank_void.n3 
   
    drugbank: time taken: 91 seconds

    omim: