Event Causality Identification Based on Large Language Model-Constructed Graph Networks
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摘要:
为提高文档级事件因果关系识别的准确率,首先利用大语言模型所包含的隐性知识,从文档中筛选出与目标事件相关的其他事件,构建事件候选集;其次,将事件候选集组合成事件关系全连接图,并对其进行条件约束,通过条件约束将事件关系全连接图简化为事件关系约束图,减少图中无关事件的噪声传递;最后,以自注意力机制计算图网络中任一节点对其他节点的影响,并利用带有焦点损失的二分类损失函数训练模型,进一步缓解了因果关系识别中的假阳性问题. 研究结果表明:模型在事件因果关系识别任务中,Causal-TimeBank数据集句内事件对因果识别的精确率达到77.3%;EventStoryLine数据集句内事件对因果识别的精确率达到75.2%,句间事件对识别的F1-score达到60.6%,文档级事件对识别的F1-score达到59.6%.
Abstract:To enhance the accuracy of document-level event causality identification, the implicit knowledge within large language models was first leveraged to filter out events related to the target event from the document, constructing a candidate event set. Next, the candidate event set was organized into a fully connected event relationship graph, which was then subjected to conditional constraints. These constraints simplified the fully connected graph into a constrained event relationship graph, reducing noise propagation from irrelevant events. Finally, a self-attention mechanism was used to compute the influence of any node on other nodes in the graph network, and the model was trained with a binary classification loss function incorporating focal loss, further mitigating false positives in causality identification. Experimental results show that in the causality identification tasks, the model achieves a precision of 77.3% for intra-sentence event pair causality identification on the Causal-TimeBank dataset. On the EventStoryLine dataset, it achieves a precision of 75.2% for intra-sentence event pair causality identification, an F1-score of 60.6% for inter-sentence event pair identification, and an F1-score of 59.6% for document-level event pair identification.
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Key words:
- event causality extraction /
- deep learning /
- graph network /
- large language model /
- attention mechanism
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表 1 大语言模型选择事件图模块流程
Table 1. Process of selecting event graph module in large language models
模块:大语言模型选择事件图模块 Input:文档$ D $,提示Prompt,Llama
Output:筛选事件集$ {E}_{1} $1 通过文档$ D $获得初始句子集合$ {S}_{0} $; 2 删除$ {S}_{0} $没有事件的句子得到新句子集合$ S $; 3 通过$ S $获得文档内全部事件$ {E}_{0} $; 4 For $ {e}_{t} $,$ {e}_{n} $ in $ {E}_{0} $: 5 通过$ {e}_{t} $获得$ {s}_{t} $,通过$ {e}_{n} $获得$ {s}_{n} $; 6 ($ {s}_{t} $ + $ {s}_{n} $ + $ S $ + Prompt)送入Llama模型; 7 Llama模型生成事件相关句; 8 通过事件相关句获得相关事件; 9 ($ {e}_{t} $ + $ {e}_{n} $ + 相关事件)组合成为$ {E}_{1} $; 10 End; 表 2 预测-真值混淆矩阵
Table 2. Predicted and true value confusion matrix
预测 正样本 负样本 预测为真 正阳(NTP) 假阳(NTN) 预测为假 假阴(NFP) 正阴(NFN) 表 3 模型超参数设置
Table 3. Hyperparameter settings of model
超参数 数值 学习率 2×10−5 批量大小/批 1 训练轮数/轮 20 丢弃率 0.1 权重衰减 0.01 表 4 句子级事件因果实验结果比较
Table 4. Comparison of sentence-level event causality experiment results
% 模型 EventStoryLine Causal-TimeBank P/% R/% F1/% P/% R/% F1/% GPT-3.5-turbo[16] 27.6 80.2 41.0 7.0 82.6 12.8 GPT-4.0[16] 27.2 94.7 42.2 6.1 97.4 11.5 CHEER[8] 56.9 69.6 62.6 56.4 69.5 62.3 ERGO 57.5 72.0 63.9 62.1 61.3 61.7 KADE[10] 62.1 68.8 65.3 67.9 64.6 66.2 HOTECI[15] 66.1 72.3 69.1 71.1 65.9 68.4 DFP[22] 55.9 69.8 62.1 63.7 64.2 58.5 GenSORL[23] 65.6 63.3 64.6 60.1 53.3 56.3 C3NET[24] 60.5 73.6 66.4 60.2 72.8 65.9 LLM4GL 75.2 46.3 54.7 77.3 59.2 67.1 表 5 在EventStoryLine数据集上的句间事件因果实验结果比较
Table 5. Comparison of intra-sentence event causality experiment results on EventStoryLine dataset
表 6 在EventStoryLine数据集上的消融实验结果比较
Table 6. Comparison of ablation experiment results on EventStoryLine dataset
模型 Long-
Former编码器LLM
OptionRECG P/% R/% F1/% LLM4GL1 √ × × 33.3 63.0 39.4 LLM4GL2 √ × √ 40.9 45.7 44.1 LLM4GL3 √ √ × 40.1 45.8 43.2 LLM4GL4 × √ √ 47.8 57.2 52.1 LLM4GL √ √ √ 59.1 60.7 59.6 表 7 在EventStoryLine数据集上的定性实验结果比较
Table 7. Comparison of qualitative experiment results on EventStoryLine dataset
事件对 GT BERT LLM4GL (shot,shooting) 是 是 是 (shielding,confessed) 否 是 否 (shot,shielding) 是 否 是 (attack,reports) 否 否 否 (shooting,attack) 是 否 是 (shielding,attack) 是 是 是 (shooting,confessed) 否 是 否 $\vdots $ $\vdots $ $\vdots $ $\vdots $ 表 8 在EventStoryLine数据集上Top k 实验结果
Table 8. Top k experiment results on EventStoryLine dataset
k P/% R/% F1/% 0 43.4 55.2 48.6 2 56.2 58.6 56.1 3 59.1 60.7 59.6 4 57.8 57.3 57.4 -
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