The algorithm breaks all ties uniformly at random. Interestingly, the algorithm is robust to this randomness: we run the algorithm on the human PPI network 30 times using different random seeds, which results in 94.2% overlap between the resulting 30 DSs. The average DS size over the 30 runs is 1,817+1 nodes, out of which 1,711 (i.e., 94.2%) appear in all of the 30 DSs. Hence, given that such a large proportion of any DS is in all DSs, any DS is representative of all of them. Therefore, we continue further analyses of one of the DSs.