SIDE: Representation Learning in Signed Directed Networks

Given a signed directed network, how can we learn node representations which fully encode structural information of the network including sign and direction of edges? Node representation learning or network embedding learns a mapping of each node to a vector. The mapping encodes structural information on network, providing low-dimensional dense node features for general machine learning and data mining frameworks. Since many social networks allow trust (friend) and distrust (enemy) relationships described by signed and directed edges, generalizing network embedding method to learn from sign and direction information in networks is crucial. In addition, social theories are critical tool in signed network analysis. However, none of the existing methods supports all of the desired properties: considering sign, direction, and social theoretical interpretation. In this paper, we propose SIDE, a general network embedding method that represents both sign and direction of edges in the embedding space. SIDE carefully formulates and optimizes likelihood over both direct and indirect signed connections. We provide socio-psychological interpretation for each component of likelihood function. We prove linear scalability of our algorithm and propose additional optimization techniques to reduce the training time and improve accuracy. Through extensive experiments on real-world signed directed networks, we show that SIDE effectively encodes structural information into the learned embedding.