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NCGNN: Node-level Capsule Graph Neural Network

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 Added by Rui Yang
 Publication date 2020
and research's language is English




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Message passing has evolved as an effective tool for designing Graph Neural Networks (GNNs). However, most existing works naively sum or average all the neighboring features to update node representations, which suffers from the following limitations: (1) lack of interpretability to identify crucial node features for GNNs prediction; (2) over-smoothing issue where repeated averaging aggregates excessive noise, making features of nodes in different classes over-mixed and thus indistinguishable. In this paper, we propose the Node-level Capsule Graph Neural Network (NCGNN) to address these issues with an improved message passing scheme. Specifically, NCGNN represents nodes as groups of capsules, in which each capsule extracts distinctive features of its corresponding node. For each node-level capsule, a novel dynamic routing procedure is developed to adaptively select appropriate capsules for aggregation from a subgraph identified by the designed graph filter. Consequently, as only the advantageous capsules are aggregated and harmful noise is restrained, over-mixing features of interacting nodes in different classes tends to be avoided to relieve the over-smoothing issue. Furthermore, since the graph filter and the dynamic routing identify a subgraph and a subset of node features that are most influential for the prediction of the model, NCGNN is inherently interpretable and exempt from complex post-hoc explanations. Extensive experiments on six node classification benchmarks demonstrate that NCGNN can well address the over-smoothing issue and outperforms the state of the arts by producing better node embeddings for classification.



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143 - Jinyu Yang , Peilin Zhao , Yu Rong 2020
Graph Neural Networks (GNNs) draw their strength from explicitly modeling the topological information of structured data. However, existing GNNs suffer from limited capability in capturing the hierarchical graph representation which plays an important role in graph classification. In this paper, we innovatively propose hierarchical graph capsule network (HGCN) that can jointly learn node embeddings and extract graph hierarchies. Specifically, disentangled graph capsules are established by identifying heterogeneous factors underlying each node, such that their instantiation parameters represent different properties of the same entity. To learn the hierarchical representation, HGCN characterizes the part-whole relationship between lower-level capsules (part) and higher-level capsules (whole) by explicitly considering the structure information among the parts. Experimental studies demonstrate the effectiveness of HGCN and the contribution of each component.
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Graph Neural Networks (GNNs) are efficient approaches to process graph-structured data. Modelling long-distance node relations is essential for GNN training and applications. However, conventional GNNs suffer from bad performance in modelling long-distance node relations due to limited-layer information propagation. Existing studies focus on building deep GNN architectures, which face the over-smoothing issue and cannot model node relations in particularly long distance. To address this issue, we propose to model long-distance node relations by simply relying on shallow GNN architectures with two solutions: (1) Implicitly modelling by learning to predict node pair relations (2) Explicitly modelling by adding edges between nodes that potentially have the same label. To combine our two solutions, we propose a model-agnostic training framework named HighwayGraph, which overcomes the challenge of insufficient labeled nodes by sampling node pairs from the training set and adopting the self-training method. Extensive experimental results show that our HighwayGraph achieves consistent and significant improvements over four representative GNNs on three benchmark datasets.
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