While Named Entity Recognition (NER) is a widely studied task, making inferences of entities with only a few labeled data has been challenging, especially for entities with nested structures. Unlike flat entities, entities and their nested entities are more likely to have similar semantic feature representations, drastically increasing difficulties in classifying different entity categories in the few-shot setting. Although prior work has briefly discussed nested structures in the context of few-shot learning, to our best knowledge, this paper is the first one specifically dedicated to studying the few-shot nested NER task. Leveraging contextual dependency to distinguish nested entities, we propose a Biaffine-based Contrastive Learning (BCL) framework. We first design a Biaffine span representation module for learning the contextual span dependency representation for each entity span rather than only learning its semantic representation. We then merge these two representations by the residual connection to distinguish nested entities. Finally, we build a contrastive learning framework to adjust the representation distribution for larger margin boundaries and more generalized domain transfer learning ability. We conducted experimental studies on three English, German, and Russian nested NER datasets. The results show that the BCL outperformed three baseline models on the 1-shot and 5-shot tasks in terms of F1 score.

几个名称的实体识别（NER）使我们能够使用很少的标记示例为新域构建一个NER系统。但是，该任务的现有原型网络具有大致估计的标签依赖性和紧密分布的原型，因此经常导致错误分类。为了解决上述问题，我们提出了EP-NET，这是一个实体级原型网络，通过分散分布的原型增强。EP-NET构建实体级原型，并认为文本跨度为候选实体，因此它不再需要标签依赖性。此外，EP-NET从头开始训练原型，以分散分配它们，并使用空间投影将跨度与嵌入空间中的原型对齐。两项评估任务和少量网络设置的实验结果表明，EP-NET在整体性能方面始终优于先前的强大模型。广泛的分析进一步验证了EP-NET的有效性。

Few-shot named entity recognition (NER) targets generalizing to unseen labels and/or domains with few labeled examples. Existing metric learning methods compute token-level similarities between query and support sets, but are not able to fully incorporate label semantics into modeling. To address this issue, we propose a simple method to largely improve metric learning for NER: 1) multiple prompt schemas are designed to enhance label semantics; 2) we propose a novel architecture to effectively combine multiple prompt-based representations. Empirically, our method achieves new state-of-the-art (SOTA) results under 16 of the 18 considered settings, substantially outperforming the previous SOTA by an average of 8.84% and a maximum of 34.51% in relative gains of micro F1. Our code is available at https://github.com/AChen-qaq/ProML.

对于自然语言处理中的许多任务，将知识从一个域转移到另一个领域至关重要，尤其是当目标域中的可用数据量受到限制时。在这项工作中，我们在指定实体识别（NER）的背景下提出了一种新颖的域适应方法。我们提出了一种两步方法，该方法由可变基本模块和模板模块组成，该模块在简单的描述模式的帮助下利用了预训练的语言模型中捕获的知识。我们的方法简单而通用，可以在几次射击和零拍设置中应用。评估我们在许多不同数据集中的轻量级方法表明，它可以将最新基准的性能提高2-5％的F1分数。

生物医学机器阅读理解（生物医学MRC）旨在理解复杂的生物医学叙事，并协助医疗保健专业人员从中检索信息。现代神经网络的MRC系统的高性能取决于高质量的大规模，人为宣传的培训数据集。在生物医学领域中，创建此类数据集的一个至关重要的挑战是域知识的要求，引起了标记数据的稀缺性以及从标记的通用（源）域转移学习到生物医学（目标）域的需求。然而，由于主题方差，通用和生物医学领域之间的边际分布存在差异。因此，从在通用域上训练的模型到生物医学领域的模型直接转移学会的表示可能会损害模型的性能。我们为生物医学机器阅读理解任务（BioAdapt-MRC）提供了基于对抗性学习的域适应框架，这是一种基于神经网络的方法，可解决一般和生物医学域数据之间边际分布中的差异。 Bioadapt-MRC松弛了生成伪标签的需求，以训练表现出色的生物医学MRC模型。我们通过将生物ADAPT-MRC与三种广泛使用的基准生物医学MRC数据集进行比较，从而广泛评估了生物ADAPT-MRC的性能-Bioasq-7B，BioASQ-8B和BioASQ-9B。我们的结果表明，如果不使用来自生物医学领域的任何合成或人类通知的数据，Bioadapt-MRC可以在这些数据集中实现最先进的性能。可用性：bioadapt-MRC可作为开放源项目免费获得，\ url {https://github.com/mmahbub/bioadapt-mrc}。

我们为指定实体识别（NER）提出了一个有效的双重编码框架，该框架将对比度学习用于映射候选文本跨度，并将实体类型映射到同一矢量表示空间中。先前的工作主要将NER作为序列标记或跨度分类。相反，我们将NER视为一个度量学习问题，它最大程度地提高了实体提及的向量表示之间的相似性及其类型。这使得易于处理嵌套和平坦的ner，并且可以更好地利用嘈杂的自我诉讼信号。 NER对本双重编码器制定的主要挑战在于将非实体跨度与实体提及分开。我们没有明确标记所有非实体跨度为外部（O）与大多数先前方法相同的类别（O），而是引入了一种新型的动态阈值损失，这与标准的对比度损失一起学习。实验表明，我们的方法在受到监督和远处有监督的设置中的表现良好（例如，Genia，NCBI，BC5CDR，JNLPBA）。

大多数NER方法都依赖于广泛的标记数据进行模型培训，这些数据在低资源场景中挣扎，培训数据有限。与资源丰富的源域相比，现有的主要方法通常会遇到目标域具有不同标签集的挑战，该标签集可以作为类传输和域转移得出的结论。在本文中，我们通过可拔出的提示（Lightner）提出了一个轻巧的调整范式，用于低资源。具体而言，我们构建了实体类别的统一可学习的语言器，以生成实体跨度序列和实体类别，而无需任何标签特定的分类器，从而解决了类转移问题。我们通过将可学习的参数纳入自我发言层作为指导，进一步提出了一个可插入的指导模块，该参数可以重新调节注意力并调整预训练的权重。请注意，我们仅通过修复了预训练的语言模型的整个参数来调整那些插入的模块，从而使我们的方法轻巧且灵活地适合低资源场景，并且可以更好地跨域传输知识。实验结果表明，Lightner可以在标准监督环境中获得可比的性能，并且在低资源设置中优于强大基线。代码在https://github.com/zjunlp/deepke/tree/main/main/example/ner/few-shot中。

几乎没有命名的实体识别（NER）对于在有限的资源领域中标记的实体标记至关重要，因此近年来受到了适当的关注。现有的几声方法主要在域内设置下进行评估。相比之下，对于这些固有的忠实模型如何使用一些标记的域内示例在跨域NER中执行的方式知之甚少。本文提出了一种两步以理性为中心的数据增强方法，以提高模型的泛化能力。几个数据集中的结果表明，与先前的最新方法相比，我们的模型无形方法可显着提高跨域NER任务的性能，包括反事实数据增强和及时调用方法。我们的代码可在\ url {https://github.com/lifan-yuan/factmix}上获得。

As an important fine-grained sentiment analysis problem, aspect-based sentiment analysis (ABSA), aiming to analyze and understand people's opinions at the aspect level, has been attracting considerable interest in the last decade. To handle ABSA in different scenarios, various tasks are introduced for analyzing different sentiment elements and their relations, including the aspect term, aspect category, opinion term, and sentiment polarity. Unlike early ABSA works focusing on a single sentiment element, many compound ABSA tasks involving multiple elements have been studied in recent years for capturing more complete aspect-level sentiment information. However, a systematic review of various ABSA tasks and their corresponding solutions is still lacking, which we aim to fill in this survey. More specifically, we provide a new taxonomy for ABSA which organizes existing studies from the axes of concerned sentiment elements, with an emphasis on recent advances of compound ABSA tasks. From the perspective of solutions, we summarize the utilization of pre-trained language models for ABSA, which improved the performance of ABSA to a new stage. Besides, techniques for building more practical ABSA systems in cross-domain/lingual scenarios are discussed. Finally, we review some emerging topics and discuss some open challenges to outlook potential future directions of ABSA.

关系提取（RE）是指在输入文本中提取关系三元组。现有的基于神经工作的系统在很大程度上依赖于手动标记的培训数据，但是仍然有很多域中不存在足够的标记数据。受到基于距离的几弹性实体识别方法的启发，我们根据序列标记的关节提取方法提出了几个弹出任务的定义，并为任务提出了一些弹出框架。此外，我们将两个实际的序列标记模型应用于我们的框架（称为少数Tplinker和几杆Bitt），并在从公共数据集构建的两个少量RE任务上实现了可靠的结果。

Prompt learning recently become an effective linguistic tool to motivate the PLMs' knowledge on few-shot-setting tasks. However, studies have shown the lack of robustness still exists in prompt learning, since suitable initialization of continuous prompt and expert-first manual prompt are essential in fine-tuning process. What is more, human also utilize their comparative ability to motivate their existing knowledge for distinguishing different examples. Motivated by this, we explore how to use contrastive samples to strengthen prompt learning. In detail, we first propose our model ConsPrompt combining with prompt encoding network, contrastive sampling module, and contrastive scoring module. Subsequently, two sampling strategies, similarity-based and label-based strategies, are introduced to realize differential contrastive learning. The effectiveness of proposed ConsPrompt is demonstrated in five different few-shot learning tasks and shown the similarity-based sampling strategy is more effective than label-based in combining contrastive learning. Our results also exhibits the state-of-the-art performance and robustness in different few-shot settings, which proves that the ConsPrompt could be assumed as a better knowledge probe to motivate PLMs.

指定的实体识别任务是信息提取的核心任务之一。单词歧义和单词缩写是命名实体低识别率的重要原因。在本文中，我们提出了一种名为“实体识别模型WCL-BBCD”（与Bert-Bilstm-Crf-Dbpedia的单词对比学习），结合了对比度学习的概念。该模型首先在文本中训练句子对，计算句子对通过余弦的相似性中的单词对之间的相似性，以及通过相似性通过相似性来命名实体识别任务的BERT模型，以减轻单词歧义。然后，将微调的BERT模型与Bilstm-CRF模型相结合，以执行指定的实体识别任务。最后，将识别结果与先验知识（例如知识图）结合使用，以减轻单词缩写引起的低速问题的识别。实验结果表明，我们的模型在Conll-2003英语数据集和Ontonotes V5英语数据集上优于其他类似的模型方法。

跨度提取，旨在从纯文本中提取文本跨度（如单词或短语），是信息提取中的基本过程。最近的作品介绍了通过将跨度提取任务正式化为问题（QA正式化）的跨度提取任务来提高文本表示，以实现最先进的表现。然而，QA正规化并没有充分利用标签知识并遭受培训/推理的低效率。为了解决这些问题，我们介绍了一种新的范例来整合标签知识，并进一步提出一个小说模型，明确有效地将标签知识集成到文本表示中。具体而言，它独立地编码文本和标签注释，然后将标签知识集成到文本表示中，并使用精心设计的语义融合模块进行文本表示。我们在三个典型的跨度提取任务中进行广泛的实验：扁平的网，嵌套网和事件检测。实证结果表明，我们的方法在四个基准测试中实现了最先进的性能，而且分别将培训时间和推理时间降低76％和77％，与QA形式化范例相比。我们的代码和数据可在https://github.com/apkepers/lear中获得。

Cross-domain few-shot relation extraction poses a great challenge for the existing few-shot learning methods and domain adaptation methods when the source domain and target domain have large discrepancies. This paper proposes a method by combining the idea of few-shot learning and domain adaptation to deal with this problem. In the proposed method, an encoder, learned by optimizing a representation loss and an adversarial loss, is used to extract the relation of sentences in the source and target domain. The representation loss, including a cross-entropy loss and a contrastive loss, makes the encoder extract the relation of the source domain and keep the geometric structure of the classes in the source domain. And the adversarial loss is used to merge the source domain and target domain. The experimental results on the benchmark FewRel dataset demonstrate that the proposed method can outperform some state-of-the-art methods.

Metric-based meta-learning is one of the de facto standards in few-shot learning. It composes of representation learning and metrics calculation designs. Previous works construct class representations in different ways, varying from mean output embedding to covariance and distributions. However, using embeddings in space lacks expressivity and cannot capture class information robustly, while statistical complex modeling poses difficulty to metric designs. In this work, we use tensor fields (``areas'') to model classes from the geometrical perspective for few-shot learning. We present a simple and effective method, dubbed hypersphere prototypes (HyperProto), where class information is represented by hyperspheres with dynamic sizes with two sets of learnable parameters: the hypersphere's center and the radius. Extending from points to areas, hyperspheres are much more expressive than embeddings. Moreover, it is more convenient to perform metric-based classification with hypersphere prototypes than statistical modeling, as we only need to calculate the distance from a data point to the surface of the hypersphere. Following this idea, we also develop two variants of prototypes under other measurements. Extensive experiments and analysis on few-shot learning tasks across NLP and CV and comparison with 20+ competitive baselines demonstrate the effectiveness of our approach.

提示方法被认为是几次自然语言处理的关键进展之一。最近对基于离散令牌的``硬提示''转移到连续``软提示''的最新研究，这些提示将可学习的向量用作伪提示代币并实现更好的性能。尽管显示出有希望的前景，但观察到这些软宣传的方法在很大程度上依赖良好的初始化来生效。不幸的是，获得软提示的完美初始化需要了解内在语言模型的工作和精心设计，这绝非易事，必须从头开始重新启动每个新任务。为了解决此问题，我们提出了一种称为Metaprompting的广义软提示方法，该方法采用了良好认可的模型 - 静态元学习算法，以自动找到更好的及时初始化，从而快速适应新的促进任务。问题并在四个不同的数据集上带来了显着改善（1次设置的准确性提高了6分），从而实现了新的最新性能。

当大型训练数据集不可用于低资源域时，命名实体识别（NER）模型通常表现不佳。最近，预先训练大规模语言模型已成为应对数据稀缺问题的有希望的方向。然而，语言建模和ner任务之间的潜在差异可能会限制模型的性能，并且由于收集的网数据集通常很小或大而是低质量，因此已经研究了NER任务的预训练。在本文中，我们构建了一个具有相对高质量的大规模核心语料库，我们基于创建的数据集预先列车。实验结果表明，我们的预训练模型可以显着优于八大域的低资源场景中的百合形和其他强基线。此外，实体表示的可视化进一步指示Ner-BERT用于对各种实体进行分类的有效性。

与伯特（Bert）等语言模型相比，已证明知识增强语言表示的预培训模型在知识基础构建任务（即〜关系提取）中更有效。这些知识增强的语言模型将知识纳入预训练中，以生成实体或关系的表示。但是，现有方法通常用单独的嵌入表示每个实体。结果，这些方法难以代表播出的实体和大量参数，在其基础代币模型之上（即〜变压器），必须使用，并且可以处理的实体数量为由于内存限制，实践限制。此外，现有模型仍然难以同时代表实体和关系。为了解决这些问题，我们提出了一个新的预培训模型，该模型分别从图书中学习实体和关系的表示形式，并分别在文本中跨越跨度。通过使用SPAN模块有效地编码跨度，我们的模型可以代表实体及其关系，但所需的参数比现有模型更少。我们通过从Wikipedia中提取的知识图对我们的模型进行了预训练，并在广泛的监督和无监督的信息提取任务上进行了测试。结果表明，我们的模型比基线学习对实体和关系的表现更好，而在监督的设置中，微调我们的模型始终优于罗伯塔，并在信息提取任务上取得了竞争成果。

Few-shot relation extraction (FSRE) aims at recognizing unseen relations by learning with merely a handful of annotated instances. To generalize to new relations more effectively, this paper proposes a novel pipeline for the FSRE task based on queRy-information guided Attention and adaptive Prototype fuSion, namely RAPS. Specifically, RAPS first derives the relation prototype by the query-information guided attention module, which exploits rich interactive information between the support instances and the query instances, in order to obtain more accurate initial prototype representations. Then RAPS elaborately combines the derived initial prototype with the relation information by the adaptive prototype fusion mechanism to get the integrated prototype for both train and prediction. Experiments on the benchmark dataset FewRel 1.0 show a significant improvement of our method against state-of-the-art methods.

Aspect-based sentiment analysis (ABSA) aims at extracting opinionated aspect terms in review texts and determining their sentiment polarities, which is widely studied in both academia and industry. As a fine-grained classification task, the annotation cost is extremely high. Domain adaptation is a popular solution to alleviate the data deficiency issue in new domains by transferring common knowledge across domains. Most cross-domain ABSA studies are based on structure correspondence learning (SCL), and use pivot features to construct auxiliary tasks for narrowing down the gap between domains. However, their pivot-based auxiliary tasks can only transfer knowledge of aspect terms but not sentiment, limiting the performance of existing models. In this work, we propose a novel Syntax-guided Domain Adaptation Model, named SDAM, for more effective cross-domain ABSA. SDAM exploits syntactic structure similarities for building pseudo training instances, during which aspect terms of target domain are explicitly related to sentiment polarities. Besides, we propose a syntax-based BERT mask language model for further capturing domain-invariant features. Finally, to alleviate the sentiment inconsistency issue in multi-gram aspect terms, we introduce a span-based joint aspect term and sentiment analysis module into the cross-domain End2End ABSA. Experiments on five benchmark datasets show that our model consistently outperforms the state-of-the-art baselines with respect to Micro-F1 metric for the cross-domain End2End ABSA task.