code: public static SortedSet<StructureName> getRepresentatives(int sequenceIdentity) {
  		SortedSet<StructureName> representatives = new TreeSet<StructureName>();
  
  		if (!seqIdentities.contains(sequenceIdentity)) {
  			System.err.println("Error: representative chains are not available for %sequence identity: "
  							+ sequenceIdentity);
  			return representatives;
  		}
  
  
  		try {
  
  			URL u = new URL(clusterUrl + sequenceIdentity);
  
  			InputStream stream = URLConnectionTools.getInputStream(u, 60000);
  
  			String xml = null;
  
  			if (stream != null) {
  				xml = JFatCatClient.convertStreamToString(stream);
  
  				SortedSet<String> reps = RepresentativeXMLConverter.fromXML(xml);
  
  				for (String s : reps) {
  					StructureName k = new StructureName(s);
  					representatives.add(k);
  				}
  
  			}
  
  		} catch (Exception e) {
  			e.printStackTrace();
  		}
  
  		return representatives;
  	}
docs: Returns a representative set of PDB protein chains at the specified sequence
  identity cutoff. See http://www.pdb.org/pdb/statistics/clusterStatistics.do
  for more information.
  @param sequenceIdentity sequence identity threshold
  @return PdbChainKey set of representatives