The basis unit of clustering rules of NG in Fig 3 can be represented as Fig 4, which indicates that: if the co-occurrence number of Ii and Ck is Uik, and that of Ii and Zij is dij, the number of Zij belonging to community Ck is αijk. In this paper, the main idea of CM is to determine whether node Zij can be allocated to community Ck, but the clustering rule in Fig 4 still fails to intuitively judge the credibility of node Zij belongings to community Ck. As a result, BPF is adopted to figure out the credibility of a node belonging to each community.