6. The method of claim 5 , further comprising: updating the predefined weight of each of the one or more first nodes and the predefined weight of each of the one or more second nodes in the generated graph.
7. The method of claim 6 , wherein the updating of the predefined weight comprises determining a weight for each node of the one or more first nodes and the one or more second nodes using 
 minΣ( i,j )∈ E|a i −a j | where E corresponds to an extended keyword graph, a i corresponds to a weight by which a unigram probability estimate for keyword I is incremented, and a j is defined for keywords in set M=L∪D, L and D correspond to nodes and edges.