John Boaz Lee

Link Prediction in a Modified Heterogeneous Bibliographic Network

Researchers have discovered, in recent years, the advantages of modeling complex systems using heterogeneous information networks. These networks are comprised of heterogeneous sets of nodes and edges that better represent the different entities and relationships often found in the real world. Although heterogeneous networks provide a richer semantic view of the data, the added complexity makes it difficult to directly apply existing techniques that work well on homogeneous networks. In this paper, we propose a graph modification process that alters an existing heterogeneous bibliographic network into another network, with the purpose of highlighting the important relations in the bibliographic network. Several importance scores, some adopted from existing work and others defined in this work, are then used to measure the importance of links in the modified network. The link prediction problem is studied on the modified network by implementing a random walk-based algorithm on the network. The importance scores and the structure of the modified graph are used to guide a random walker towards relevant parts of the graph, i.e. towards nodes to which new links will be created in the future. The different properties of the proposed algorithm are evaluated experimentally on a real world bibliographic network, the DBLP. Results show that the proposed method outperforms the state-of-the-art supervised technique as well as various approaches based on topology and node attributes.

Patch Reviewer Recommendation in OSS Projects

In an Open Source Software (OSS) project, many developers contribute by submitting source code patches. To maintain the quality of the code, certain experienced developers review each patch before it can be applied or committed. Ideally, within a short amount of time after its submission, a patch is assigned to a reviewer and reviewed. In the real world, however, many large and active OSS projects evolve at a rapid pace and the core developers can get swamped with a large number of patches to review. Furthermore, since these core members may not always be available or may choose to leave the project, it can be challenging, at times, to find a good reviewer for a patch. In this paper, we propose a graph-based method to automatically recommend the most suitable reviewers for a patch. To evaluate our method, we conducted experiments to predict the developers who will apply new changes to the source code in the Eclipse project. Our method achieved an average recall of 0.84 for top-5 predictions and a recall of 0.94 for top-10 predictions.

Voting Behavior Analysis in the Election of Wikipedia Admins

Past work analyzing elections in online domains has largely ignored the underlying social networks present in such environments. Here, we study the Wikipedia Request for Adminship (RfA) process within the context of a social network and pinpoint several factors influencing different stages of the voting process. The facets explored are: election participation, decision making in elections, and election outcome. We find that voters tend to participate in elections that their contacts have participated in. Furthermore, there is evidence showing that an individuals decision-making is influenced by his contacts actions. The properties of voters within the social graph were also studied, results reveal that candidates who gain the support of an influential coalition tend to succeed in elections.

Graph Classification using Structural Attention

Graph classification is a problem with practical applications in many different domains. To solve this problem, one usually calculates certain graph statistics (i.e., graph features) that help discriminate between graphs of different classes. When calculating such features, most existing approaches process the entire graph. In a graphlet-based approach, for instance, the entire graph is processed to get the total count of different graphlets or subgraphs. In many real-world applications, however, graphs can be noisy with discriminative patterns confined to certain regions in the graph only. In this work, we study the problem of attention-based graph classification. The use of attention allows us to focus on small but informative parts of the graph, avoiding noise in the rest of the graph. We present a novel RNN model, called the Graph Attention Model (GAM), that processes only a portion of the graph by adaptively selecting a sequence of informative nodes. Experimental results on multiple real-world datasets show that the proposed method is competitive against various well-known methods in graph classification even though our method is limited to only a portion of the graph.

Continuous-Time Dynamic Network Embeddings.

Networks evolve continuously over time with the addition, deletion, and changing of links and nodes. Although many networks contain this type of temporal information, the majority of research in network representation learning has focused on static snapshots of the graph and has largely ignored the temporal dynamics of the network. In this work, we describe a general framework for incorporating temporal information into network embedding methods. The framework gives rise to methods for learning time-respecting embeddings from continuous-time dynamic networks. Overall, the experiments demonstrate the effectiveness of the proposed framework and dynamic network embedding approach as it achieves an average gain of 11.9% across all methods and graphs. The results indicate that modeling temporal dependencies in graphs is important for learning appropriate and meaningful network representations.