Revealing Bridges in Social Networks

Social groups and networks are ubiquitous, and each network member typically has a role or roles in associated interactions. One such member identified in social network literature is a bridge, which connects two or more groups, and is an element of only one of the groups; inferred from literature (e.g., Granovetter, 1973; Rogers and Kincaid, 1981) is the notion that bridges play a key role in networks. At different times and for various reasons, network and group components may be unrevealed. An example is a terrorist network; the terrorists may know who comprises their network, but a military or security organization that is attempting to dismantle the organization is unlikely to know all of the individuals and/or their interactions and roles. Consequently, the ability to characterize and detect bridges could be valuable in the national security structure's efforts since such members can play a key role in networks. This article addresses the associated problem: Given a network of groups, for which the information about each group consists of individuals, their attributes, and (only) their intra-group relations, identify which individual (or individuals) is a bridge node. Additionally, an approach is presented for detecting that a bridge is missing from a group, i.e., inferring the existence of a bridge from group data that does not contain the bridge in its membership, the bridge's attributes, nor the bridge's contacts. Accordingly, a method for recreating the ground truth network once a bridge's existence has been detected is given. Lastly, the potential application of these approaches to networks other than social networks is discussed.