## 4 Case Study: Citation Network Analysis Using ACL Data Corpus
### Discussion  
In Figure 3, we visualize the ACL ARC citations network that forms eight communities, having more than 5% of total nodes and edges. For better visualization, nodes of total degree <29 (2.5% of the total nodes) are filtered from the citations network. We used Gephi with ForceAtlas2 and Novelrap layout settings for the network visualization. The community colors in the network are assigned automatically using a community-detection algorithm (modularity), and the size of nodes is determined by the betweenness centrality measure, with min size = 10 and max size = 50. The network shows the strong interconnectivity between clusters 18, 8, 4, and cluster 16. Cluster 20 is the largest, covering more than 16% nodes of the total nodes. We also observed that among the 16% nodes (papers) covered by cluster 20, only 46% edges (citations) (including 44% uses and 2% extends) links belong to the important citations. Moreover, in cluster 20, nearly 54% of the total edges and nodes belong to the non-important class, having 20% background, 22% compare or contrast, 7% motivation, and 5% future classes citations.  
Figure 4 presents the nodes-wise representation of the ACL ARC citations network. Of the total nodes, only 24% of papers belong to the ACL whereas the remaining 75%  
Figure 3: Visualization of the ACL ARC citation network. The citation network illustrates a color-based community structure, nodes having the same colors belong to the same community.  
\begin{table}
\begin{tabular}{c c c c c c c c} \hline \hline
**Layout Settings** & **Type** & **Nodes** & **Edges** & **AD** & **M** & **CC** & **C Co** & **APL** \\ \hline ForceAtlas2 Novelrap & Community detection & 2757 & 22,049 & 15.99 & 0.60 & 26 & 0.125 & 3.53 \\ OpenOrd & Edge-based analysis & 919 & 4806 & 10.45 & 0.60 & 19 & 0.14 & 3.50 \\ \hline \hline \end{tabular}
\end{table}
Table 3: Network-level properties of ACL ARC citations network for community detection and edges-based analysis across Average Degree (AD), modularity (M), connected component (CC), clustering coefficient (C Co), average path length (APL).  
of papers are external papers. The blue color indicates the ACL paper and the red color represents the external papers. It is important to note that in the ACL citations network, the majority of the citations come from outside the ACL.  
Furthermore, among the total nodes, the top 1% nodes with respect to node degree are taken to visualize the citation network, based on their citation functions such as important (uses, extends) and non-important (background, compare or contrast, motivation, future). Figure 4(a) illustrates the binary class citations edges between the papers. Of the total citations, only 37.84% of citations are important, and the remaining 62.16% are non-important citations. Similarly, Figure 4(b) presents the citations edges based on the multi-class citations functions. We find \"uses\" and \"background\" classes at the top of the list, with 34.64% and 32.8% citations received, respectively. The motivation, future, and compare or contrast classes have more than 5% citations instances, while the \"extends\" class received less than 5% citations.  
Figure 4: Visualization of the ACL ARC citations network to visualize the ACL papers and papers outside the ACL.  
Figure 5: Visualization of the ACL ARC citations network to only visualize the citation classes: (**a**) presents the binary class citations edges and (**b**) illustrates the multi-class citation edges between the nodes. The top 1% of total nodes with respect to the node degree are taken to visualize the citations network. We used the OpenOrd layout in Gephi to see these citations edges.