We use the normalized weight for edge defined by equation (1) or(2) for the element m ij .
m ij =e(p i , n j ) if there is an edge between program node p i and noun node n j , m ij =e(n i , n j ) if there is an edge between noun node p i and noun node n j , and m ij =0 if there is no edge between node i and node j.