知识密集型语言任务（苏格兰信）通常需要大量信息来提供正确的答案。解决此问题的一种流行范式是将搜索系统与机器读取器相结合，前者检索支持证据，后者检查它们以产生答案。最近，读者组成部分在大规模预培养的生成模型的帮助下见证了重大进展。同时，搜索组件中的大多数现有解决方案都依赖于传统的``索引 - retrieve-then-Rank''管道，该管道遭受了巨大的内存足迹和端到端优化的困难。受到最新构建基于模型的IR模型的努力的启发，我们建议用新颖的单步生成模型替换传统的多步搜索管道，该模型可以极大地简化搜索过程并以端到端的方式进行优化。我们表明，可以通过一组经过适当设计的预训练任务来学习强大的生成检索模型，并被采用以通过进一步的微调来改善各种下游苏格兰短裙任务。我们将预训练的生成检索模型命名为Copusbrain，因为有关该语料库的所有信息均以其参数进行编码，而无需构造其他索引。经验结果表明，在苏格兰语基准上的检索任务并建立了新的最新性能，Copusbrain可以极大地超过强大的基准。我们还表明，在零农源和低资源设置下，科体班运行良好。

近年来，在应用预训练的语言模型（例如Bert）上，取得了巨大进展，以获取信息检索（IR）任务。在网页中通常使用的超链接已被利用用于设计预训练目标。例如，超链接的锚文本已用于模拟查询，从而构建了巨大的查询文档对以进行预训练。但是，作为跨越两个网页的桥梁，尚未完全探索超链接的潜力。在这项工作中，我们专注于建模通过超链接连接的两个文档之间的关系，并为临时检索设计一个新的预训练目标。具体而言，我们将文档之间的关系分为四组：无链接，单向链接，对称链接和最相关的对称链接。通过比较从相邻组采样的两个文档，该模型可以逐渐提高其捕获匹配信号的能力。我们提出了一个渐进的超链接预测（{php}）框架，以探索预训练中超链接的利用。对两个大规模临时检索数据集和六个提问数据集的实验结果证明了其优于现有的预训练方法。

Entities, as important carriers of real-world knowledge, play a key role in many NLP tasks. We focus on incorporating entity knowledge into an encoder-decoder framework for informative text generation. Existing approaches tried to index, retrieve, and read external documents as evidence, but they suffered from a large computational overhead. In this work, we propose an encoder-decoder framework with an entity memory, namely EDMem. The entity knowledge is stored in the memory as latent representations, and the memory is pre-trained on Wikipedia along with encoder-decoder parameters. To precisely generate entity names, we design three decoding methods to constrain entity generation by linking entities in the memory. EDMem is a unified framework that can be used on various entity-intensive question answering and generation tasks. Extensive experimental results show that EDMem outperforms both memory-based auto-encoder models and non-memory encoder-decoder models.

大型语言模型在各种任务上显示出令人印象深刻的几次结果。但是，当知识是此类结果的关键时，就像问题回答和事实检查之类的任务一样，似乎需要存储知识的大量参数计数。众所周知，检索增强模型可以在不需要多个参数的情况下在知识密集的任务上表现出色，但是目前尚不清楚它们是否在几个弹药设置中工作。在这项工作中，我们介绍了地图集，这是一个经过精心设计和预先训练的增强语言模型，能够通过很少的培训示例学习知识密集型任务。我们对包括MMLU，苏格兰短裙和归类等各种任务进行评估，并研究文档索引内容的影响，表明它可以很容易地进行更新。值得注意的是，在自然问题上仅使用64个示例在自然问题上达到超过42 \％的准确性，尽管参数少了50倍，但比540B参数模型的表现优于540b参数模型。

Large pre-trained language models have been shown to store factual knowledge in their parameters, and achieve state-of-the-art results when fine-tuned on downstream NLP tasks. However, their ability to access and precisely manipulate knowledge is still limited, and hence on knowledge-intensive tasks, their performance lags behind task-specific architectures. Additionally, providing provenance for their decisions and updating their world knowledge remain open research problems. Pre-trained models with a differentiable access mechanism to explicit nonparametric memory can overcome this issue, but have so far been only investigated for extractive downstream tasks. We explore a general-purpose fine-tuning recipe for retrieval-augmented generation (RAG) -models which combine pre-trained parametric and non-parametric memory for language generation. We introduce RAG models where the parametric memory is a pre-trained seq2seq model and the non-parametric memory is a dense vector index of Wikipedia, accessed with a pre-trained neural retriever. We compare two RAG formulations, one which conditions on the same retrieved passages across the whole generated sequence, and another which can use different passages per token. We fine-tune and evaluate our models on a wide range of knowledge-intensive NLP tasks and set the state of the art on three open domain QA tasks, outperforming parametric seq2seq models and task-specific retrieve-and-extract architectures. For language generation tasks, we find that RAG models generate more specific, diverse and factual language than a state-of-the-art parametric-only seq2seq baseline.

Systems for knowledge-intensive tasks such as open-domain question answering (QA) usually consist of two stages: efficient retrieval of relevant documents from a large corpus and detailed reading of the selected documents to generate answers. Retrievers and readers are usually modeled separately, which necessitates a cumbersome implementation and is hard to train and adapt in an end-to-end fashion. In this paper, we revisit this design and eschew the separate architecture and training in favor of a single Transformer that performs Retrieval as Attention (ReAtt), and end-to-end training solely based on supervision from the end QA task. We demonstrate for the first time that a single model trained end-to-end can achieve both competitive retrieval and QA performance, matching or slightly outperforming state-of-the-art separately trained retrievers and readers. Moreover, end-to-end adaptation significantly boosts its performance on out-of-domain datasets in both supervised and unsupervised settings, making our model a simple and adaptable solution for knowledge-intensive tasks. Code and models are available at https://github.com/jzbjyb/ReAtt.

We present Pre-trained Machine Reader (PMR), a novel method to retrofit Pre-trained Language Models (PLMs) into Machine Reading Comprehension (MRC) models without acquiring labeled data. PMR is capable of resolving the discrepancy between model pre-training and downstream fine-tuning of existing PLMs, and provides a unified solver for tackling various extraction tasks. To achieve this, we construct a large volume of general-purpose and high-quality MRC-style training data with the help of Wikipedia hyperlinks and design a Wiki Anchor Extraction task to guide the MRC-style pre-training process. Although conceptually simple, PMR is particularly effective in solving extraction tasks including Extractive Question Answering and Named Entity Recognition, where it shows tremendous improvements over previous approaches especially under low-resource settings. Moreover, viewing sequence classification task as a special case of extraction task in our MRC formulation, PMR is even capable to extract high-quality rationales to explain the classification process, providing more explainability of the predictions.

最近的开放式域问题的作品应答使用检索器模型引用外部知识库，可选地重新映射与单独的重新编制模型，并使用另一个读取器模型生成答案。尽管执行相关任务，但模型具有单独的参数，并且在训练期间略微耦合。在这项工作中，我们建议将猎犬和重新划分为依次应用于变压器架构内的硬注视机制，并将所产生的计算表示给读者送入。在这个奇异模型架构中，隐藏的表示从搬运者逐渐改进到Reranker到读者，这更有效地利用模型容量，并且当我们以端到端的方式训练时，还导致更好的梯度流动。我们还提出了一种预先训练的方法，以有效地培训这种架构。我们评估我们的自然问题和TriviaQA Open DataSets的模型以及固定参数预算，我们的模型优于以前的最先进模型1.0和0.7精确匹配分数。

信息检索是自然语言处理中的重要组成部分，用于知识密集型任务，如问题应答和事实检查。最近，信息检索已经看到基于神经网络的密集检索器的出现，作为基于术语频率的典型稀疏方法的替代方案。这些模型在数据集和任务中获得了最先进的结果，其中提供了大型训练集。但是，它们不会很好地转移到没有培训数据的新域或应用程序，并且通常因未经监督的术语 - 频率方法（例如BM25）的术语频率方法而言。因此，自然问题是如果没有监督，是否有可能训练密集的索取。在这项工作中，我们探讨了对比学习的限制，作为培训无人监督的密集检索的一种方式，并表明它导致强烈的检索性能。更确切地说，我们在15个数据集中出现了我们的模型胜过BM25的Beir基准测试。此外，当有几千例的示例可用时，我们显示微调我们的模型，与BM25相比，这些模型导致强大的改进。最后，当在MS-Marco数据集上微调之前用作预训练时，我们的技术在Beir基准上获得最先进的结果。

我们提出了一种用于在生成答案时将信息与多个检索文件中的信息组合的可检索增强的开放式开放式开放式开放域问题训练方法。我们将检索决策模拟作为相关文件集的潜在变量。由于通过对所检索的文件集的边缘化，因此使用期望最大化算法估计这一点。我们迭代地估计我们的潜在变量的价值（给定问题的这些相关文档集），然后使用此估计来更新检索器和读取器参数。我们假设这种端到端的训练允许训练信号流到读者，然后比上演明智的训练更好地流到猎犬。这导致检索器能够为问题和读者选择更多相关文档，这些文件在更准确的文档中培训以生成答案。三个基准数据集的实验表明，我们所提出的方法优于所有现有的相当大小的方法2-3％绝对精确匹配点，实现了新的最先进的结果。我们的结果还展示了学习检索以改善答复的可行性，而无明确监督检索决策。

当前的密集文本检索模型面临两个典型的挑战。首先，他们采用暹罗双重编码架构来独立编码查询和文档，以快速索引和搜索，同时忽略了较细粒度的术语互动。这导致了次优的召回表现。其次，他们的模型培训高度依赖于负面抽样技术，以在其对比损失中构建负面文档。为了应对这些挑战，我们提出了对抗猎犬速率（AR2），它由双重编码猎犬加上跨编码器等级组成。这两种模型是根据最小群体对手的共同优化的：检索员学会了检索负面文件以欺骗排名者，而排名者学会了对包括地面和检索的候选人进行排名，并提供渐进的直接反馈对双编码器检索器。通过这款对抗性游戏，猎犬逐渐生产出更难的负面文件来训练更好的排名者，而跨编码器排名者提供了渐进式反馈以改善检索器。我们在三个基准测试基准上评估AR2。实验结果表明，AR2始终如一地胜过现有的致密回收者方法，并在所有这些方法上实现了新的最新结果。这包括对自然问题的改进R@5％至77.9％（+2.1％），Triviaqa R@5％至78.2％（+1.4）和MS-Marco MRR@10％至39.5％（+1.3％）。代码和型号可在https://github.com/microsoft/ar2上找到。

正如GPT-3和T5所证明的那样，随着参数空间变得越来越大，变压器具有能力。但是，对于需要大量知识的任务，非参数存储器允许模型在计算成本和GPU内存需求的次线性增加中急剧增长。诸如RAG和Realm之类的最新模型已将检索引入条件生成。这些模型结合了从一系列语料库中的神经初始检索。我们基于这一研究，提出了RE2G，该研究将神经初始检索和重新融合到基于巴特的序列到序列的生成中。我们的阅读方法还允许从无与伦比分数的来源合并结果，从而实现BM25和神经初始检索的合奏。为了训练我们的系统端到端，我们引入了一种新颖的知识蒸馏变体，以在目标序列输出上仅使用地面真理来训练初始检索，重读者和生成。我们在四个不同的任务中发现了很大的收益：零击插槽填充，问答，事实检查和对话，相对增长了9％至34％，比以前的苏格兰短裙排行榜上的最先前的排行榜相比。我们将代码作为开源提供，网址为https://github.com/ibm/kgi-slot-filling/tree/re2g。

Dense retrieval aims to map queries and passages into low-dimensional vector space for efficient similarity measuring, showing promising effectiveness in various large-scale retrieval tasks. Since most existing methods commonly adopt pre-trained Transformers (e.g. BERT) for parameter initialization, some work focuses on proposing new pre-training tasks for compressing the useful semantic information from passages into dense vectors, achieving remarkable performances. However, it is still challenging to effectively capture the rich semantic information and relations about passages into the dense vectors via one single particular pre-training task. In this work, we propose a multi-task pre-trained model, MASTER, that unifies and integrates multiple pre-training tasks with different learning objectives under the bottlenecked masked autoencoder architecture. Concretely, MASTER utilizes a multi-decoder architecture to integrate three types of pre-training tasks: corrupted passages recovering, related passage recovering and PLMs outputs recovering. By incorporating a shared deep encoder, we construct a representation bottleneck in our architecture, compressing the abundant semantic information across tasks into dense vectors. The first two types of tasks concentrate on capturing the semantic information of passages and relationships among them within the pre-training corpus. The third one can capture the knowledge beyond the corpus from external PLMs (e.g. GPT-2). Extensive experiments on several large-scale passage retrieval datasets have shown that our approach outperforms the previous state-of-the-art dense retrieval methods. Our code and data are publicly released in https://github.com/microsoft/SimXNS

Recent work on open domain question answering (QA) assumes strong supervision of the supporting evidence and/or assumes a blackbox information retrieval (IR) system to retrieve evidence candidates. We argue that both are suboptimal, since gold evidence is not always available, and QA is fundamentally different from IR. We show for the first time that it is possible to jointly learn the retriever and reader from question-answer string pairs and without any IR system. In this setting, evidence retrieval from all of Wikipedia is treated as a latent variable. Since this is impractical to learn from scratch, we pre-train the retriever with an Inverse Cloze Task. We evaluate on open versions of five QA datasets. On datasets where the questioner already knows the answer, a traditional IR system such as BM25 is sufficient. On datasets where a user is genuinely seeking an answer, we show that learned retrieval is crucial, outperforming BM25 by up to 19 points in exact match.

已经表明，在一个域上训练的双编码器经常概括到其他域以获取检索任务。一种广泛的信念是，一个双编码器的瓶颈层，其中最终得分仅仅是查询向量和通道向量之间的点产品，它过于局限，使得双编码器是用于域外概括的有效检索模型。在本文中，我们通过缩放双编码器模型的大小{\ em同时保持固定的瓶颈嵌入尺寸固定的瓶颈的大小来挑战这一信念。令人惊讶的是，令人惊讶的是，缩放模型尺寸会对各种缩放提高检索任务，特别是对于域外泛化。实验结果表明，我们的双编码器，\ textbf {g} enovalizable \ textbf {t} eTrievers（gtr），优先级％colbert〜\ cite {khattab2020colbertt}和现有的稀疏和密集的索取Beir DataSet〜\ Cite {Thakur2021Beir}显着显着。最令人惊讶的是，我们的消融研究发现，GTR是非常数据的高效，因为它只需要10 \％MARCO监督数据，以实现最佳域的性能。所有GTR模型都在https://tfhub.dev/google/collections/gtr/1发布。

知识密集型任务，例如开放域问题答案（QA），需要访问大量的世界知识或领域知识。知识密集型任务的一种常见方法是采用检索到阅读的管道，该管道首先从诸如Wikipedia之类的外部语料库中检索少数相关的上下文文档，然后预测在检索文档的条件下得到答案。在本文中，我们提出了一种新的观点，可以通过用大型语言模型生成器代替文档检索器来解决知识密集型任务。我们称我们的方法生成-Read Read（GenRead），该方法首先提示大型语言模型根据给定问题生成上下文文档，然后读取生成的文档以产生最终答案。此外，我们提出了一种基于聚类的提示方法，该方法选择了不同的提示，从而产生了涵盖不同观点的生成文档，从而更好地回忆了可接受的答案。我们对三个不同的知识密集任务进行了广泛的实验，包括开放域质量检查，事实检查和对话系统。值得注意的是，GenRead在Triviaqa和WebQ上实现了71.6和54.4的精确匹配分数，显着超过了最先进的检索到+4.0和+3.9的最先进的dpr-fid，而无需从任何外部知识源中检索任何文档。最后，我们证明可以通过结合检索和生成来进一步提高模型性能。

We present Hybrid Infused Reranking for Passages Retrieval (HYRR), a framework for training rerankers based on a hybrid of BM25 and neural retrieval models. Retrievers based on hybrid models have been shown to outperform both BM25 and neural models alone. Our approach exploits this improved performance when training a reranker, leading to a robust reranking model. The reranker, a cross-attention neural model, is shown to be robust to different first-stage retrieval systems, achieving better performance than rerankers simply trained upon the first-stage retrievers in the multi-stage systems. We present evaluations on a supervised passage retrieval task using MS MARCO and zero-shot retrieval tasks using BEIR. The empirical results show strong performance on both evaluations.

对于开放式域问题的密集检索已被证明通过在问题通道对的大型数据集上培训来实现令人印象深刻的性能。我们调查是否可以以自我监督的方式学习密集的检索，并有效地应用没有任何注释。我们观察到这种情况下的检索斗争的现有借用模型，并提出了一种设计用于检索的新预制方案：重复跨度检索。我们在文档中使用经常性跨度来创建用于对比学习的伪示例。由此产生的模型 - 蜘蛛 - 在广泛的ODQA数据集上没有任何示例，并且与BM25具有竞争力，具有强烈的稀疏基线。此外，蜘蛛通常优于DPR在其他数据集的问题上培训的DPR培训的强大基线。我们将蜘蛛与BM25结合的混合猎犬改进了所有数据集的组件，并且通常与域中DPR模型具有竞争力，这些模型培训数万例培训。

Open-domain question answering relies on efficient passage retrieval to select candidate contexts, where traditional sparse vector space models, such as TF-IDF or BM25, are the de facto method. In this work, we show that retrieval can be practically implemented using dense representations alone, where embeddings are learned from a small number of questions and passages by a simple dualencoder framework. When evaluated on a wide range of open-domain QA datasets, our dense retriever outperforms a strong Lucene-BM25 system greatly by 9%-19% absolute in terms of top-20 passage retrieval accuracy, and helps our end-to-end QA system establish new state-of-the-art on multiple open-domain QA benchmarks. 1 * Equal contribution 1 The code and trained models have been released at https://github.com/facebookresearch/DPR.

This paper presents E5, a family of state-of-the-art text embeddings that transfer well to a wide range of tasks. The model is trained in a contrastive manner with weak supervision signals from our curated large-scale text pair dataset (called CCPairs). E5 can be readily used as a general-purpose embedding model for any tasks requiring a single-vector representation of texts such as retrieval, clustering, and classification, achieving strong performance in both zero-shot and fine-tuned settings. We conduct extensive evaluations on 56 datasets from the BEIR and MTEB benchmarks. For zero-shot settings, E5 is the first model that outperforms the strong BM25 baseline on the BEIR retrieval benchmark without using any labeled data. When fine-tuned, E5 obtains the best results on the MTEB benchmark, beating existing embedding models with 40x more parameters.