Web Mining and Social Networking: Techniques and ... - tud.ttu.ee

90 5 Web Linkage Mining5.2 Co-citation and Bibliographic CouplingCitation analysis is an area of bibliometric research, which studies citations to establish therelationship between authors and their work. When a paper cites another paper, a relationship(or link) is establish between the papers. Citation analysis uses these relationships (links) toperform various types of analysis. We will introduce two specific types of citation analysisrelated to the HITS algorithm, co-citation and bibliographic coupling.5.2.1 Co-citationCo-citation is used to measure the similarity of two documents in clustering. If paper i and jare cited together by many papers, it means that i and j have a strong relationship or similarity.The more papers they are cited together, the stronger their relationship is. Figure 5.1 belowshows this main idea.Fig. 5.1. Paper i and j are co-cited by kLet L be the citation matrix. Each cell of the matrix is defined as follows: L ij = 1 if paper icites paper j, and 0 otherwise. Co-citation (denoted by C ij ) is defined as the number of papersthat co-cite i and j, and is computed with( )C ij = ∑ k=1,...nL ki L kj = L T L(5.1)ijWhere, n is the total number of papers. A square matrix C can be formed with C ij , and it iscalled the co-citation matrix.5.2.2 Bibliographic CouplingBibliographic coupling is also a similarity measure of two papers in clustering. We can lookat the bibliographic coupling as the mirror image of co-citation. The main idea here is that ifpaper i and paper j both cite paperk, they may be said to be related, even though they do notcite each other directly (see Fig. 5.2 below).B ij is the number of papers that are cited by both papers i and paper j:(B ij = ∑ ) k=1,...nL ik L jk = LL T (5.2)ijWhere, n is the total number of papers. A square matrix B can be formed with B ij , and it iscalled the bibliographic coupling matrix.