论文标题
嵌套命名实体识别的令人尴尬但强大的基线
An Embarrassingly Easy but Strong Baseline for Nested Named Entity Recognition
论文作者
论文摘要
命名实体识别（NER）是检测和对实体跨越文本的任务。当实体跨越彼此之间的重叠时，此问题被称为嵌套NER。基于跨度的方法已被广泛用于应对嵌套的NER。这些方法中的大多数都会获得分数$ n \ times n $矩阵，其中$ n $表示句子的长度，每个条目对应于跨度。但是，先前的工作忽略了分数矩阵中的空间关系。在本文中，我们建议使用卷积神经网络（CNN）在得分矩阵中对这些空间关系进行建模。尽管很简单，但在三个常用的嵌套NER数据集中进行的实验表明，我们的模型超过了几种具有相同预训练的编码器的最近提出的方法。进一步的分析表明，使用CNN可以帮助该模型找到更多嵌套实体。此外，我们发现不同的论文对三个嵌套的NER数据集使用了不同的句子引导，这将影响比较。因此，我们发布了一个预处理脚本，以促进将来的比较。
Named entity recognition (NER) is the task to detect and classify the entity spans in the text. When entity spans overlap between each other, this problem is named as nested NER. Span-based methods have been widely used to tackle the nested NER. Most of these methods will get a score $n \times n$ matrix, where $n$ means the length of sentence, and each entry corresponds to a span. However, previous work ignores spatial relations in the score matrix. In this paper, we propose using Convolutional Neural Network (CNN) to model these spatial relations in the score matrix. Despite being simple, experiments in three commonly used nested NER datasets show that our model surpasses several recently proposed methods with the same pre-trained encoders. Further analysis shows that using CNN can help the model find more nested entities. Besides, we found that different papers used different sentence tokenizations for the three nested NER datasets, which will influence the comparison. Thus, we release a pre-processing script to facilitate future comparison.
