Modern multi-document summarization (MDS) methods are based on transformer architectures. They generate state of the art summaries, but lack explainability. We focus on graph-based transformer models for MDS as they gained recent popularity. We aim to improve the explainability of the graph-based MDS by analyzing their attention weights. In a graph-based MDS such as GraphSum, vertices represent the textual units, while the edges form some similarity graph over the units. We compare GraphSum's performance utilizing different textual units, i. e., sentences versus paragraphs, on two news benchmark datasets, namely WikiSum and MultiNews. Our experiments show that paragraph-level representations provide the best summarization performance. Thus, we subsequently focus oAnalysisn analyzing the paragraph-level attention weights of GraphSum's multi-heads and decoding layers in order to improve the explainability of a transformer-based MDS model. As a reference metric, we calculate the ROUGE scores between the input paragraphs and each sentence in the generated summary, which indicate source origin information via text similarity. We observe a high correlation between the attention weights and this reference metric, especially on the the later decoding layers of the transformer architecture. Finally, we investigate if the generated summaries follow a pattern of positional bias by extracting which paragraph provided the most information for each generated summary. Our results show that there is a high correlation between the position in the summary and the source origin.

与单案摘要相比，抽象性多文件摘要（MDS）对其冗长和链接的来源的表示和覆盖范围提出了挑战。这项研究开发了一个平行的层次变压器（PHT），具有MDS的注意对齐。通过合并单词和段落级的多头注意，PHT的层次结构可以更好地处理令牌和文档级别的依赖项。为了指导解码到更好的源文档覆盖范围，然后将注意力调整机制引入以校准光束搜索，并预测的最佳注意力分布。根据Wikisum数据，进行了全面的评估，以测试拟议的体系结构对MD的改进。通过更好地处理内部和跨文档的信息，结果胭脂和人类评估都表明，我们的分层模型以相对较低的计算成本生成较高质量的摘要。

诸如学术文章和商业报告之类的长期文件一直是详细说明重要问题和需要额外关注的复杂主题的标准格式。自动汇总系统可以有效地将长文档置于简短而简洁的文本中，以封装最重要的信息，从而在帮助读者的理解中很重要。最近，随着神经体系结构的出现，已经做出了重大的研究工作，以推动自动文本摘要系统，以及有关将这些系统扩展到长期文档领域的挑战的大量研究。在这项调查中，我们提供了有关长期文档摘要的研究的全面概述，以及其研究环境的三个主要组成部分的系统评估：基准数据集，汇总模型和评估指标。对于每个组成部分，我们在长期汇总的背景下组织文献，并进行经验分析，以扩大有关当前研究进度的观点。实证分析包括一项研究基准数据集的内在特征，摘要模型的多维分析以及摘要评估指标的综述。根据总体发现，我们通过提出可能在这个快速增长的领域中提出未来探索的方向来得出结论。

多文件摘要（MDS）是信息聚合的有效工具，它从与主题相关文档集群生成信息和简洁的摘要。我们的调查是，首先，系统地概述了最近的基于深度学习的MDS模型。我们提出了一种新的分类学，总结神经网络的设计策略，并进行全面的最先进的概要。我们突出了在现有文献中很少讨论的各种客观函数之间的差异。最后，我们提出了与这个新的和令人兴奋的领域有关的几个方向。

多文件科学摘要（MDSS）旨在为与主题相关的科学论文群生成连贯和简洁的摘要。此任务需要精确理解纸张内容以及对交叉纸关系的准确建模。知识图为文档传达了紧凑且可解释的结构化信息，这使其非常适合内容建模和关系建模。在本文中，我们提出了KGSUM，这是一个MDSS模型，以编码和解码过程中的知识图为中心。具体而言，在编码过程中，提出了两个基于图的模块，以将知识图信息纳入纸张编码，而在解码过程中，我们通过以描述性句子的形式首先生成摘要的知识图，提出了一个两阶段解码器。 ，然后生成最终摘要。经验结果表明，所提出的体系结构对多XSCIENCE数据集的基准进行了实质性改进。

Nowadays, time-stamped web documents related to a general news query floods spread throughout the Internet, and timeline summarization targets concisely summarizing the evolution trajectory of events along the timeline. Unlike traditional document summarization, timeline summarization needs to model the time series information of the input events and summarize important events in chronological order. To tackle this challenge, in this paper, we propose a Unified Timeline Summarizer (UTS) that can generate abstractive and extractive timeline summaries in time order. Concretely, in the encoder part, we propose a graph-based event encoder that relates multiple events according to their content dependency and learns a global representation of each event. In the decoder part, to ensure the chronological order of the abstractive summary, we propose to extract the feature of event-level attention in its generation process with sequential information remained and use it to simulate the evolutionary attention of the ground truth summary. The event-level attention can also be used to assist in extracting summary, where the extracted summary also comes in time sequence. We augment the previous Chinese large-scale timeline summarization dataset and collect a new English timeline dataset. Extensive experiments conducted on these datasets and on the out-of-domain Timeline 17 dataset show that UTS achieves state-of-the-art performance in terms of both automatic and human evaluations.

Bidirectional Encoder Representations from Transformers (BERT; Devlin et al. 2019) represents the latest incarnation of pretrained language models which have recently advanced a wide range of natural language processing tasks. In this paper, we showcase how BERT can be usefully applied in text summarization and propose a general framework for both extractive and abstractive models. We introduce a novel document-level encoder based on BERT which is able to express the semantics of a document and obtain representations for its sentences. Our extractive model is built on top of this encoder by stacking several intersentence Transformer layers. For abstractive summarization, we propose a new fine-tuning schedule which adopts different optimizers for the encoder and the decoder as a means of alleviating the mismatch between the two (the former is pretrained while the latter is not). We also demonstrate that a two-staged fine-tuning approach can further boost the quality of the generated summaries. Experiments on three datasets show that our model achieves stateof-the-art results across the board in both extractive and abstractive settings. 1

多文件摘要中的一个关键挑战是捕获区分单个文档摘要（SDS）和多文件摘要（MDS）的输入文档之间的关系。现有的MDS工作很少解决此问题。一种有效的方法是编码文档位置信息，以帮助模型捕获跨文档关系。但是，现有的MDS模型（例如基于变压器的模型）仅考虑令牌级的位置信息。此外，这些模型无法捕获句子的语言结构，这不可避免地会引起生成的摘要中的混乱。因此，在本文中，我们提出了可以与MDS的变压器体系结构融合的文档意识到的位置编码和语言引导的编码。对于文档感知的位置编码，我们引入了一项通用协议，以指导文档编码功能的选择。对于语言引导的编码，我们建议使用简单但有效的非线性编码学习者进行特征学习，将句法依赖关系嵌入依赖关系掩码中。广泛的实验表明，所提出的模型可以生成高质量的摘要。

由于免费的在线百科全书具有大量内容，因此Wikipedia和Wikidata是许多自然语言处理（NLP）任务的关键，例如信息检索，知识基础构建，机器翻译，文本分类和文本摘要。在本文中，我们介绍了Wikides，这是一个新颖的数据集，用于为文本摘要问题提供Wikipedia文章的简短描述。该数据集由6987个主题上的80K英语样本组成。我们设置了一种两阶段的摘要方法 - 描述生成（I阶段）和候选排名（II阶段）作为一种依赖于转移和对比学习的强大方法。对于描述生成，与其他小规模的预训练模型相比，T5和BART表现出了优越性。通过将对比度学习与Beam Search的不同输入一起应用，基于度量的排名模型优于直接描述生成模型，在主题独立拆分和独立于主题的独立拆分中，最高可达22个胭脂。此外，第II期中的结果描述得到了人类评估的支持，其中45.33％以上，而I阶段的23.66％则支持针对黄金描述。在情感分析方面，生成的描述无法有效地从段落中捕获所有情感极性，同时从黄金描述中更好地完成此任务。自动产生的新描述减少了人类为创建它们的努力，并丰富了基于Wikidata的知识图。我们的论文对Wikipedia和Wikidata产生了实际影响，因为有成千上万的描述。最后，我们预计Wikides将成为从短段落中捕获显着信息的相关作品的有用数据集。策划的数据集可公开可用：https：//github.com/declare-lab/wikides。

尽管最近的抽象摘要有所改善，但大多数当前方法都会产生与源文档不一致的摘要，从而严重限制了其在现实世界应用中的信任和使用。最近的作品显示了使用文本或依赖性弧形识别事实错误识别的有希望的改进；但是，他们不会同时考虑整个语义图。为此，我们提出了Factgraph，该方法将文档分解为结构化含义表示（MR），更适合于事实评估。太太描述了核心语义概念及其关系，以规范形式汇总文档和摘要中的主要内容，并减少数据稀疏性。 Factgraph使用与结构感知适配器增强的图形编码器编码此类图，以根据图形连接性捕获概念之间的交互，以及使用基于适配器的文本编码器的文本表示。在不同基准上进行评估事实的实验表明，事实图的表现优于先前的方法高达15％。此外，Factgraph改善了识别内容可验证性错误的性能，并更好地捕获了附近级别的事实不一致。

学术研究是解决以前从未解决过的问题的探索活动。通过这种性质，每个学术研究工作都需要进行文献审查，以区分其Novelties尚未通过事先作品解决。在自然语言处理中，该文献综述通常在“相关工作”部分下进行。鉴于研究文件的其余部分和引用的论文列表，自动相关工作生成的任务旨在自动生成“相关工作”部分。虽然这项任务是在10年前提出的，但直到最近，它被认为是作为科学多文件摘要问题的变种。然而，即使在今天，尚未标准化了自动相关工作和引用文本生成的问题。在这项调查中，我们进行了一个元研究，从问题制定，数据集收集，方法方法，绩效评估和未来前景的角度来比较相关工作的现有文献，以便为读者洞察到国家的进步 - 最内容的研究，以及如何进行未来的研究。我们还调查了我们建议未来工作要考虑整合的相关研究领域。

在过去的几十年中，知识感知的方法增强了一系列自然语言处理应用。随着收集的动力，最近在文档摘要中引起了知识，这是自然语言处理应用之一。先前的作品报告说，知识包裹的文档摘要在产生卓越的消化方面表现出色，尤其是在信息性，连贯性和事实一致性方面。本文追求对将知识嵌入文档摘要的最先进方法论进行的首次系统调查。特别是，我们提出了新的分类法，以概括文档摘要观点下的知识和知识嵌入。我们进一步探讨了如何在嵌入文档摘要模型的学习体系结构时，尤其是深度学习模型的学习架构。最后，我们讨论了这个主题和未来方向的挑战。

Text summarization is a user-preference based task, i.e., for one document, users often have different priorities for summary. As a key aspect of customization in summarization, granularity is used to measure the semantic coverage between the summary and source document. However, developing systems that can generate summaries with customizable semantic coverage is still an under-explored topic. In this paper, we propose the first unsupervised multi-granularity summarization framework, GranuSum. We take events as the basic semantic units of the source documents and propose to rank these events by their salience. We also develop a model to summarize input documents with given events as anchors and hints. By inputting different numbers of events, GranuSum is capable of producing multi-granular summaries in an unsupervised manner. Meanwhile, we annotate a new benchmark GranuDUC that contains multiple summaries at different granularities for each document cluster. Experimental results confirm the substantial superiority of GranuSum on multi-granularity summarization over strong baselines. Further, by exploiting the event information, GranuSum also exhibits state-of-the-art performance under the conventional unsupervised abstractive setting. Dataset for this paper can be found at: https://github.com/maszhongming/GranuDUC

维基百科是可理解知识的重要自由来源。尽管如此，巴西葡萄牙维基百科仍然缺乏对许多科目的描述。为了扩大巴西维基百科，我们贡献了Plsum，这是一种从多个描述性网站生成类似的Wiki的抽象摘要的框架。该框架具有提取阶段，然后是抽象。特别是，对于抽象阶段，我们微调并比较了变压器神经网络，PTT5和啰覆的最近最近的变化。为了微调和评估模型，我们创建了一个具有数千个示例的数据集，将参考网站链接到维基百科。我们的结果表明，可以从巴西葡萄牙语网上内容生成有意义的抽象摘要。

Information overloading requires the need for summarizers to extract salient information from the text. Currently, there is an overload of dialogue data due to the rise of virtual communication platforms. The rise of Covid-19 has led people to rely on online communication platforms like Zoom, Slack, Microsoft Teams, Discord, etc. to conduct their company meetings. Instead of going through the entire meeting transcripts, people can use meeting summarizers to select useful data. Nevertheless, there is a lack of comprehensive surveys in the field of meeting summarizers. In this survey, we aim to cover recent meeting summarization techniques. Our survey offers a general overview of text summarization along with datasets and evaluation metrics for meeting summarization. We also provide the performance of each summarizer on a leaderboard. We conclude our survey with different challenges in this domain and potential research opportunities for future researchers.

We introduce extreme summarization, a new single-document summarization task which does not favor extractive strategies and calls for an abstractive modeling approach. The idea is to create a short, one-sentence news summary answering the question "What is the article about?". We collect a real-world, large scale dataset for this task by harvesting online articles from the British Broadcasting Corporation (BBC). We propose a novel abstractive model which is conditioned on the article's topics and based entirely on convolutional neural networks. We demonstrate experimentally that this architecture captures longrange dependencies in a document and recognizes pertinent content, outperforming an oracle extractive system and state-of-the-art abstractive approaches when evaluated automatically and by humans. 1

查询聚焦的文本摘要（QFTS）任务旨在构建基于给定查询的文本文档摘要的构建系统。解决此任务的关键挑战是缺乏培训摘要模型的大量标记数据。在本文中，我们通过探索一系列域适应技术来解决这一挑战。鉴于最近在广泛的自然语言处理任务中进行预先接受的变压器模型的成功，我们利用此类模型为单文档和多文件方案的QFTS任务产生抽象摘要。对于域适应，我们使用预先训练的变压器的摘要模型应用了各种技术，包括转移学习，弱监督学习和远程监督。六个数据集的广泛实验表明，我们所提出的方法非常有效地为QFTS任务产生抽象摘要，同时在一组自动和人类评估指标上设置新的最先进的结果。

现有以查询为中心的摘要数据集的大小有限，使培训数据驱动的摘要模型提出了挑战。同时，以查询为重点的摘要语料库的手动构造昂贵且耗时。在本文中，我们使用Wikipedia自动收集超过280，000个示例的大型以查询为中心的摘要数据集（名为Wikiref），这可以用作数据增强的手段。我们还开发了一个基于BERT的以查询为重点的摘要模型（Q-bert），以从文档中提取句子作为摘要。为了更好地调整包含数百万个参数的巨大模型，我们仅识别和微调一个稀疏的子网络，这对应于整个模型参数的一小部分。三个DUC基准测试的实验结果表明，在Wikiref中预先培训的模型已经达到了合理的性能。在对特定基准数据集进行了微调后，具有数据增强的模型优于强大比较系统。此外，我们提出的Q-Bert模型和子网微调都进一步改善了模型性能。该数据集可在https://aka.ms/wikiref上公开获取。

Though many algorithms can be used to automatically summarize legal case decisions, most fail to incorporate domain knowledge about how important sentences in a legal decision relate to a representation of its document structure. For example, analysis of a legal case summarization dataset demonstrates that sentences serving different types of argumentative roles in the decision appear in different sections of the document. In this work, we propose an unsupervised graph-based ranking model that uses a reweighting algorithm to exploit properties of the document structure of legal case decisions. We also explore the impact of using different methods to compute the document structure. Results on the Canadian Legal Case Law dataset show that our proposed method outperforms several strong baselines.

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.