(3) Cluster coefficient (CC)CC is a

(3) Cluster coefficient (CC)CC is a measure of the degree to which nodes in a graph tend to cluster together. The global CC is based on triples of nodes. A triplet is three nodes that are connected by either two (open triplet) or three (closed triplet) in undirected ties (Wang et al., 2016). A triangle graph therefore includes three closed triplets, one centered on each of the nodes (Albert and Barabasi, 2002). The directions of the arcs in SEIN are not considered, when calculating CC. Table 4 shows the CC of sub-event in SEIN. It is observed that only 48 sub-events can be calculated CC because other 13 sub-events only have 1 neighbor which make it impossible to have a triple. The CC of sub-events in the SEIN with the values ranged from 0 to 0.8. The more the value of CC closed to 1, the stronger the accessibility of its neighbor sub-events. It means that prevention of the sub-event which has a higher CC does not help in the SEIN prevention. Because its neighbor sub-events still have strong interrelationship. There are “Dropping luggage ”, “Accompanying riders”, and “Stop luggage falling” whose CC are higher than 0.5. What is more, the CC of rest sub-events roughly fluctuates between 0.1 to 0.5 except 12 sub-events with lowest value 0. Furthermore, the average value of CC for the entire SEIN is 0.2338.