Natural Language Processing (NLP) has been revolutionized by the use of Pre-trained Language Models (PLMs) such as BERT. Despite setting new records in nearly every NLP task, PLMs still face a number of challenges including poor interpretability, weak reasoning capability, and the need for a lot of expensive annotated data when applied to downstream tasks. By integrating external knowledge into PLMs, \textit{\underline{K}nowledge-\underline{E}nhanced \underline{P}re-trained \underline{L}anguage \underline{M}odels} (KEPLMs) have the potential to overcome the above-mentioned limitations. In this paper, we examine KEPLMs systematically through a series of studies. Specifically, we outline the common types and different formats of knowledge to be integrated into KEPLMs, detail the existing methods for building and evaluating KEPLMS, present the applications of KEPLMs in downstream tasks, and discuss the future research directions. Researchers will benefit from this survey by gaining a quick and comprehensive overview of the latest developments in this field.

Pre-trained Language Models (PLMs) which are trained on large text corpus through the self-supervised learning method, have yielded promising performance on various tasks in Natural Language Processing (NLP). However, though PLMs with huge parameters can effectively possess rich knowledge learned from massive training text and benefit downstream tasks at the fine-tuning stage, they still have some limitations such as poor reasoning ability due to the lack of external knowledge. Incorporating knowledge into PLMs has been tried to tackle these issues. In this paper, we present a comprehensive review of Knowledge-Enhanced Pre-trained Language Models (KE-PLMs) to provide a clear insight into this thriving field. We introduce appropriate taxonomies respectively for Natural Language Understanding (NLU) and Natural Language Generation (NLG) to highlight the focus of these two kinds of tasks. For NLU, we take several types of knowledge into account and divide them into four categories: linguistic knowledge, text knowledge, knowledge graph (KG), and rule knowledge. The KE-PLMs for NLG are categorized into KG-based and retrieval-based methods. Finally, we point out some promising future directions of KE-PLMs.

机器学习方法尤其是深度神经网络取得了巨大的成功，但其中许多往往依赖于一些标记的样品进行训练。在真实世界的应用中，我们经常需要通过例如具有新兴预测目标和昂贵的样本注释的动态上下文来解决样本短缺。因此，低资源学习，旨在学习具有足够资源（特别是培训样本）的强大预测模型，现在正在被广泛调查。在所有低资源学习研究中，许多人更喜欢以知识图（kg）的形式利用一些辅助信息，这对于知识表示变得越来越受欢迎，以减少对标记样本的依赖。在这项调查中，我们非常全面地审查了90美元的报纸关于两个主要的低资源学习设置 - 零射击学习（ZSL）的预测，从未出现过训练，而且很少拍摄的学习（FSL）预测的新类仅具有可用的少量标记样本。我们首先介绍了ZSL和FSL研究中使用的KGS以及现有的和潜在的KG施工解决方案，然后系统地分类和总结了KG感知ZSL和FSL方法，将它们划分为不同的范例，例如基于映射的映射，数据增强，基于传播和基于优化的。我们接下来呈现了不同的应用程序，包括计算机视觉和自然语言处理中的kg增强预测任务，还包括kg完成的任务，以及每个任务的一些典型评估资源。我们最终讨论了一些关于新学习和推理范式的方面的一些挑战和未来方向，以及高质量的KGs的建设。

Knowledge graphs (KG) have served as the key component of various natural language processing applications. Commonsense knowledge graphs (CKG) are a special type of KG, where entities and relations are composed of free-form text. However, previous works in KG completion and CKG completion suffer from long-tail relations and newly-added relations which do not have many know triples for training. In light of this, few-shot KG completion (FKGC), which requires the strengths of graph representation learning and few-shot learning, has been proposed to challenge the problem of limited annotated data. In this paper, we comprehensively survey previous attempts on such tasks in the form of a series of methods and applications. Specifically, we first introduce FKGC challenges, commonly used KGs, and CKGs. Then we systematically categorize and summarize existing works in terms of the type of KGs and the methods. Finally, we present applications of FKGC models on prediction tasks in different areas and share our thoughts on future research directions of FKGC.

Storytelling and narrative are fundamental to human experience, intertwined with our social and cultural engagement. As such, researchers have long attempted to create systems that can generate stories automatically. In recent years, powered by deep learning and massive data resources, automatic story generation has shown significant advances. However, considerable challenges, like the need for global coherence in generated stories, still hamper generative models from reaching the same storytelling ability as human narrators. To tackle these challenges, many studies seek to inject structured knowledge into the generation process, which is referred to as structure knowledge-enhanced story generation. Incorporating external knowledge can enhance the logical coherence among story events, achieve better knowledge grounding, and alleviate over-generalization and repetition problems in stories. This survey provides the latest and comprehensive review of this research field: (i) we present a systematical taxonomy regarding how existing methods integrate structured knowledge into story generation; (ii) we summarize involved story corpora, structured knowledge datasets, and evaluation metrics; (iii) we give multidimensional insights into the challenges of knowledge-enhanced story generation and cast light on promising directions for future study.

大型基于变压器的预训练的语言模型在各种知识密集的任务上取得了令人印象深刻的表现，并可以在其参数中捕获事实知识。我们认为，考虑到不断增长的知识和资源需求，在模型参数中存储大量知识是亚最佳选择。我们认为，更有效的替代方法是向模型提供对上下文相关的结构化知识的明确访问，并训练它以使用该知识。我们提出了LM核 - 实现这一目标的一般框架 - 允许从外部知识源对语言模型培训的\ textit {解耦}，并允许后者更新而不会影响已经训练的模型。实验结果表明，LM核心获得外部知识，在知识探索任务上的最先进的知识增强语言模型中实现了重要而强大的优于性能。可以有效处理知识更新；并在两个下游任务上表现良好。我们还提出了一个彻底的错误分析，突出了LM核的成功和失败。

Controllable Text Generation (CTG) is emerging area in the field of natural language generation (NLG). It is regarded as crucial for the development of advanced text generation technologies that are more natural and better meet the specific constraints in practical applications. In recent years, methods using large-scale pre-trained language models (PLMs), in particular the widely used transformer-based PLMs, have become a new paradigm of NLG, allowing generation of more diverse and fluent text. However, due to the lower level of interpretability of deep neural networks, the controllability of these methods need to be guaranteed. To this end, controllable text generation using transformer-based PLMs has become a rapidly growing yet challenging new research hotspot. A diverse range of approaches have emerged in the recent 3-4 years, targeting different CTG tasks which may require different types of controlled constraints. In this paper, we present a systematic critical review on the common tasks, main approaches and evaluation methods in this area. Finally, we discuss the challenges that the field is facing, and put forward various promising future directions. To the best of our knowledge, this is the first survey paper to summarize CTG techniques from the perspective of PLMs. We hope it can help researchers in related fields to quickly track the academic frontier, providing them with a landscape of the area and a roadmap for future research.

本文对过去二十年来对自然语言生成（NLG）的研究提供了全面的审查，特别是与数据到文本生成和文本到文本生成深度学习方法有关，以及NLG的新应用技术。该调查旨在（a）给出关于NLG核心任务的最新综合，以及该领域采用的建筑;（b）详细介绍各种NLG任务和数据集，并提请注意NLG评估中的挑战，专注于不同的评估方法及其关系;（c）强调一些未来的强调和相对近期的研究问题，因为NLG和其他人工智能领域的协同作用而增加，例如计算机视觉，文本和计算创造力。

事实证明，将先验知识纳入预训练的语言模型中对知识驱动的NLP任务有效，例如实体键入和关系提取。当前的培训程序通常通过使用知识掩盖，知识融合和知识更换将外部知识注入模型。但是，输入句子中包含的事实信息尚未完全开采，并且尚未严格检查注射的外部知识。结果，无法完全利用上下文信息，并将引入额外的噪音，或者注入的知识量受到限制。为了解决这些问题，我们提出了MLRIP，该MLRIP修改了Ernie-Baidu提出的知识掩盖策略，并引入了两阶段的实体替代策略。进行全面分析的广泛实验说明了MLRIP在军事知识驱动的NLP任务中基于BERT的模型的优势。

自动问题应答（QA）系统的目的是以时间有效的方式向用户查询提供答案。通常在数据库（或知识库）或通常被称为语料库的文件集合中找到答案。在过去的几十年里，收购知识的扩散，因此生物医学领域的新科学文章一直是指数增长。因此，即使对于领域专家，也难以跟踪域中的所有信息。随着商业搜索引擎的改进，用户可以在某些情况下键入其查询并获得最相关的一小组文档，以及在某些情况下从文档中的相关片段。但是，手动查找所需信息或答案可能仍然令人疑惑和耗时。这需要开发高效的QA系统，该系统旨在为用户提供精确和精确的答案提供了生物医学领域的自然语言问题。在本文中，我们介绍了用于开发普通域QA系统的基本方法，然后彻底调查生物医学QA系统的不同方面，包括使用结构化数据库和文本集合的基准数据集和几种提出的方​​法。我们还探讨了当前系统的局限性，并探索潜在的途径以获得进一步的进步。

预先接受的语言模型实现了最先进的导致各种自然语言处理（NLP）任务。 GPT-3表明，缩放预先训练的语言模型可以进一步利用它们的巨大潜力。最近提出了一个名为Ernie 3.0的统一框架，以预先培训大型知识增强型号，并培训了具有10亿参数的模型。 Ernie 3.0在各种NLP任务上表现出最先进的模型。为了探讨缩放的表现，我们培养了百卢比的3.0泰坦参数型号，在PaddlePaddle平台上有高达260亿参数的泰坦。此外，我们设计了一种自我监督的对抗性损失和可控语言建模损失，以使ERNIE 3.0 TITAN产生可信和可控的文本。为了减少计算开销和碳排放，我们向Ernie 3.0泰坦提出了一个在线蒸馏框架，教师模型将同时教授学生和培训。埃塞尼3.0泰坦是迄今为止最大的中国密集预训练模型。经验结果表明，Ernie 3.0泰坦在68个NLP数据集中优于最先进的模型。

Natural Language Generation (NLG) has improved exponentially in recent years thanks to the development of sequence-to-sequence deep learning technologies such as Transformer-based language models. This advancement has led to more fluent and coherent NLG, leading to improved development in downstream tasks such as abstractive summarization, dialogue generation and data-to-text generation. However, it is also apparent that deep learning based generation is prone to hallucinate unintended text, which degrades the system performance and fails to meet user expectations in many real-world scenarios. To address this issue, many studies have been presented in measuring and mitigating hallucinated texts, but these have never been reviewed in a comprehensive manner before. In this survey, we thus provide a broad overview of the research progress and challenges in the hallucination problem in NLG. The survey is organized into two parts: (1) a general overview of metrics, mitigation methods, and future directions; and (2) an overview of task-specific research progress on hallucinations in the following downstream tasks, namely abstractive summarization, dialogue generation, generative question answering, data-to-text generation, machine translation, and visual-language generation. This survey serves to facilitate collaborative efforts among researchers in tackling the challenge of hallucinated texts in NLG.

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。

自然语言处理（NLP）是一个人工智能领域，它应用信息技术来处理人类语言，在一定程度上理解并在各种应用中使用它。在过去的几年中，该领域已经迅速发展，现在采用了深层神经网络的现代变体来从大型文本语料库中提取相关模式。这项工作的主要目的是调查NLP在药理学领域的最新使用。正如我们的工作所表明的那样，NLP是药理学高度相关的信息提取和处理方法。它已被广泛使用，从智能搜索到成千上万的医疗文件到在社交媒体中找到对抗性药物相互作用的痕迹。我们将覆盖范围分为五个类别，以调查现代NLP方法论，常见的任务，相关的文本数据，知识库和有用的编程库。我们将这五个类别分为适当的子类别，描述其主要属性和想法，并以表格形式进行总结。最终的调查介绍了该领域的全面概述，对从业者和感兴趣的观察者有用。

Recent years have witnessed the resurgence of knowledge engineering which is featured by the fast growth of knowledge graphs. However, most of existing knowledge graphs are represented with pure symbols, which hurts the machine's capability to understand the real world. The multi-modalization of knowledge graphs is an inevitable key step towards the realization of human-level machine intelligence. The results of this endeavor are Multi-modal Knowledge Graphs (MMKGs). In this survey on MMKGs constructed by texts and images, we first give definitions of MMKGs, followed with the preliminaries on multi-modal tasks and techniques. We then systematically review the challenges, progresses and opportunities on the construction and application of MMKGs respectively, with detailed analyses of the strength and weakness of different solutions. We finalize this survey with open research problems relevant to MMKGs.

预训练的语言模型（PLM）在各种自然语言理解任务上取得了巨大的成功。另一方面，对PLM的简单微调对于特定于领域的任务可能是次优的，因为它们不可能涵盖所有域中的知识。尽管PLM的自适应预培训可以帮助他们获得特定于领域的知识，但需要大量的培训成本。此外，自适应预训练可能会通过造成灾难性忘记其常识来损害PLM在下游任务上的表现。为了克服PLM适应性适应性预训练的这种局限性，我们提出了一个新颖的域名适应框架，用于将PLMS创造为知识增强语言模型适应性（KALA），该框架调节了PLM的中间隐藏表示与域中的中间隐藏表示，由实体和实体和实体和实体和实体构成他们的关系事实。我们验证了Kala在问题答案中的性能，并在各个域的多个数据集上命名实体识别任务。结果表明，尽管在计算上有效，但我们的Kala在很大程度上优于适应性预训练。代码可在以下网址获得：https：//github.com/nardien/kala/。

Recent progress in pretraining language models on large textual corpora led to a surge of improvements for downstream NLP tasks. Whilst learning linguistic knowledge, these models may also be storing relational knowledge present in the training data, and may be able to answer queries structured as "fillin-the-blank" cloze statements. Language models have many advantages over structured knowledge bases: they require no schema engineering, allow practitioners to query about an open class of relations, are easy to extend to more data, and require no human supervision to train. We present an in-depth analysis of the relational knowledge already present (without fine-tuning) in a wide range of state-of-theart pretrained language models. We find that (i) without fine-tuning, BERT contains relational knowledge competitive with traditional NLP methods that have some access to oracle knowledge, (ii) BERT also does remarkably well on open-domain question answering against a supervised baseline, and (iii) certain types of factual knowledge are learned much more readily than others by standard language model pretraining approaches. The surprisingly strong ability of these models to recall factual knowledge without any fine-tuning demonstrates their potential as unsupervised open-domain QA systems. The code to reproduce our analysis is available at https: //github.com/facebookresearch/LAMA.

开放信息提取是一个重要的NLP任务，它针对从非结构化文本中提取结构化信息的目标，而无需限制关系类型或文本域。该调查文件涵盖了2007年至2022年的开放信息提取技术，重点是以前的调查未涵盖的新模型。我们从信息角度来源提出了一种新的分类方法，以适应最近的OIE技术的开发。此外，我们根据任务设置以及当前流行的数据集和模型评估指标总结了三种主要方法。鉴于全面的审查，从数据集，信息来源，输出表格，方法和评估指标方面显示了几个未来的方向。

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.

知识增强的预训练预审语言模型（Keplms）是预先接受的模型，具有从知识图中注入的关系三元组，以提高语言理解能力。为了保证有效的知识注入，之前的研究将模型与知识编码器集成，以表示从知识图表中检索的知识。知识检索和编码的操作带来了重要的计算负担，限制了在需要高推理速度的现实应用程序中使用这些模型。在本文中，我们提出了一种名为DKPLM的新型KEPLM，其在预训练，微调和推理阶段进行了预先训练的语言模型的知识注射过程，这有助于KEPLMS在现实世界场景中的应用。具体而言，我们首先检测知识感知的长尾实体作为知识注射的目标，增强了Keplms的语义理解能力，避免注入冗余信息。长尾实体的嵌入式被相关知识三元组形成的“伪令牌表示”取代。我们进一步设计了用于预培训的关系知识解码任务，以强制模型通过关系三重重建来真正了解注入的知识。实验表明，我们的模型在零拍摄知识探测任务和多种知识意识语言理解任务中显着优于其他KEPLS。我们进一步表明，由于分解机制，DKPLM具有比其他竞争模型更高的推理速度。