Fast local community discovery relying on the strength of links

Mohammadmahdi Zafarmand, Yashar Talebirad, Eric Austin, Christine Largeron, Osmar R. Zaïane

Abstract: Community detection methods aim to find nodes connected to each other more than other nodes in a graph. As they explore the entire network, global methods suffer from severe limitations when handling large networks due to their time and space complexity. Local community detection methods are based on an egocentric function aiming to find only the community containing a query node (or set of query nodes). However, existing local methods are often sensitive to which query node(s) is used to discover a particular community. Our proposed approach, called SIWO “Strong In, Weak Out,” is a novel community detection method, which can locally discover densely-connected communities precisely, deterministically, and quickly. Moreover, our experimental evaluation shows that the detected community is not dependent on the initial query node within a community. This method works in a one-node-expansion way based on the notions of strong and weak links in a graph. In short, SIWO starts with a community consisting only of the query node(s). Then it checks the set of nodes in the community’s neighborhood in each step to add the “best” node and finally returns the desired community around the given query node. It can also be used iteratively to detect the entire partitioning of a network with or without considering overlapping communities, and concurrently identify outliers that may not belong in any community. Moreover, as it does not store the entire graph into main memory, it can also be used to find the core of a community on very large networks, while there is limited time and memory available. Finally, SIWO is also able to handle weighted graphs, making SIWO a general framework for community discovery and detection in various type of social networks.