ClaHi-GAT 谣言检测《Rumor Detection on Twitter with Claim-Guided Hierarchical Graph Attention Networks》( 二 ) _生活百科

${\large \begin{array}{l}b_{i} &=&\tanh \left(F C\left(h_{x_{i}}^{c}\right)\right) \\\beta_{i} &=&\frac{\exp \left(b_{i}\right)}{\sum_{i} \exp \left(b_{i}\right)} \\\hat{s} &&=\sum_{i} \beta_{i} h_{x_{i}}^{(L)}\end{array}} $
最后将其 $\hat{S}$ 与 GAT 最后一层的平均池化图表示 $\bar{s}$ 拼接作为最终图表示，并进行分类：
$\hat{y}=\operatorname{softmax}(F C([\hat{s} \| \bar{s}]))$
3 Experiments3.1 Datasets

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3.2 Rumor Classifification PerformanceTWITTER15 分类结果：

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PHEME 分类结果：

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3.3 Ablation Study1) ClaHi-GAT/DT: Instead of the undirected interaction graph, we use the directed trees as the model input.
2) GAT+EA+SC: We simply concatenate the features of the claim with the node features at each GAT layer, to replace the claim-aware representation.
3) w/o EA: We discard the event-level (inference-based) attention as presented.
4) w/o PA: We neglect the post-level (claim-aware) attention by leaving out the gating module introduced.
5) GAT: The backbone model.
6) GCN: The vanilla graph convolutional networks with no attention.

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3.4 Evaluation of Undirected Interaction Graphs

ClaHi-GAT/DT Utilize the directional tree applied in past influential works as the modeling way instead of our proposed undirected interaction graph.
ClaHi-GAT/DTS Based on the directional tree structure similar to ClaHi-GAT/DT but the explicit interactions between sibling nodes are taken into account.
ClaHi-GAT/UD The modeling way is our undirected interaction topology but without considering the explicit correlations between sibling nodes that reply to the same target.
ClaHi-GAT In this paper, we propose to model the conversation thread as an undirected interaction graph for our claim-guided hierarchical graph attention networks.

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3.5 Early Rumor Detection

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关键点：随着 claim 的传播，或多或少会产生更多的语义信息和噪声，所以使用 claim 的信息至关重要。
举例说明：false claim 的注意力分数得分图如下：

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言下之意：错误的 post $x_2$ 会被赋予较小的权重，这就是为什么该模型早期谣言检测比较稳定的原因。
【ClaHi-GAT 谣言检测《Rumor Detection on Twitter with Claim-Guided Hierarchical Graph Attention Networks》】