Nowadays, fake news easily propagates through online social networks and becomes a grand threat to individuals and society. Assessing the authenticity of news is challenging due to its elaborately fabricated contents, making it difficult to obtain large-scale annotations for fake news data. Due to such data scarcity issues, detecting fake news tends to fail and overfit in the supervised setting. Recently, graph neural networks (GNNs) have been adopted to leverage the richer relational information among both labeled and unlabeled instances. Despite their promising results, they are inherently focused on pairwise relations between news, which can limit the expressive power for capturing fake news that spreads in a group-level. For example, detecting fake news can be more effective when we better understand relations between news pieces shared among susceptible users. To address those issues, we propose to leverage a hypergraph to represent group-wise interaction among news, while focusing on important news relations with its dual-level attention mechanism. Experiments based on two benchmark datasets show that our approach yields remarkable performance and maintains the high performance even with a small subset of labeled news data.

Few-shot node classification is tasked to provide accurate predictions for nodes from novel classes with only few representative labeled nodes. This problem has drawn tremendous attention for its projection to prevailing real-world applications, such as product categorization for newly added commodity categories on an E-commerce platform with scarce records or diagnoses for rare diseases on a patient similarity graph. To tackle such challenging label scarcity issues in the non-Euclidean graph domain, meta-learning has become a successful and predominant paradigm. More recently, inspired by the development of graph self-supervised learning, transferring pretrained node embeddings for few-shot node classification could be a promising alternative to meta-learning but remains unexposed. In this work, we empirically demonstrate the potential of an alternative framework, \textit{Transductive Linear Probing}, that transfers pretrained node embeddings, which are learned from graph contrastive learning methods. We further extend the setting of few-shot node classification from standard fully supervised to a more realistic self-supervised setting, where meta-learning methods cannot be easily deployed due to the shortage of supervision from training classes. Surprisingly, even without any ground-truth labels, transductive linear probing with self-supervised graph contrastive pretraining can outperform the state-of-the-art fully supervised meta-learning based methods under the same protocol. We hope this work can shed new light on few-shot node classification problems and foster future research on learning from scarcely labeled instances on graphs.

Most existing deep learning models are trained based on the closed-world assumption, where the test data is assumed to be drawn i.i.d. from the same distribution as the training data, known as in-distribution (ID). However, when models are deployed in an open-world scenario, test samples can be out-of-distribution (OOD) and therefore should be handled with caution. To detect such OOD samples drawn from unknown distribution, OOD detection has received increasing attention lately. However, current endeavors mostly focus on grid-structured data and its application for graph-structured data remains under-explored. Considering the fact that data labeling on graphs is commonly time-expensive and labor-intensive, in this work we study the problem of unsupervised graph OOD detection, aiming at detecting OOD graphs solely based on unlabeled ID data. To achieve this goal, we develop a new graph contrastive learning framework GOOD-D for detecting OOD graphs without using any ground-truth labels. By performing hierarchical contrastive learning on the augmented graphs generated by our perturbation-free graph data augmentation method, GOOD-D is able to capture the latent ID patterns and accurately detect OOD graphs based on the semantic inconsistency in different granularities (i.e., node-level, graph-level, and group-level). As a pioneering work in unsupervised graph-level OOD detection, we build a comprehensive benchmark to compare our proposed approach with different state-of-the-art methods. The experiment results demonstrate the superiority of our approach over different methods on various datasets.

众所周知，图形神经网络（GNN）的成功高度依赖于丰富的人类通知数据，这在实践中努力获得，并且并非总是可用的。当只有少数标记的节点可用时，如何开发高效的GNN仍在研究。尽管已证明自我训练对于半监督学习具有强大的功能，但其在图形结构数据上的应用可能会失败，因为（1）不利用较大的接收场来捕获远程节点相互作用，这加剧了传播功能的难度 - 标记节点到未标记节点的标签模式； （2）有限的标记数据使得在不同节点类别中学习良好的分离决策边界而不明确捕获基本的语义结构，这是一项挑战。为了解决捕获信息丰富的结构和语义知识的挑战，我们提出了一个新的图数据增强框架，AGST（增强图自训练），该框架由两个新的（即结构和语义）增强模块构建。 GST骨干。在这项工作中，我们研究了这个新颖的框架是否可以学习具有极有限标记节点的有效图预测模型。在有限标记节点数据的不同情况下，我们对半监督节点分类进行全面评估。实验结果证明了新的数据增强框架对节点分类的独特贡献，几乎没有标记的数据。

节点分类在各种图形挖掘任务中至关重要。在实践中，实际图通常遵循长尾分布，其中大量类仅由有限的标记节点组成。尽管图神经网络（GNN）在节点分类方面取得了显着改善，但在这种情况下，它们的性能大大降低。主要原因可以归因于由于元任务中不同节点/类分布引起的任务差异（即节点级别和类级别的方差）引起的任务差异，因此元素训练和元检验之间存在巨大的概括差距。因此，为了有效地减轻任务差异的影响，我们在少数弹出的学习设置下提出了一个任务自适应的节点分类框架。具体而言，我们首先在具有丰富标记节点的类中积累了元知识。然后，我们通过提出的任务自适应模块将这些知识转移到具有有限标记的节点的类别中。特别是，为了适应元任务之间的不同节点/类分布，我们建议三个基本模块以执行\ emph {node-level}，\ emph {class-level}和\ emph {task-emph {task-level}适应元任务分别。这样，我们的框架可以对不同的元任务进行适应，从而提高元测试任务上的模型概括性能。在四个普遍的节点分类数据集上进行了广泛的实验，证明了我们的框架优于最先进的基线。我们的代码可在https://github.com/songw-sw/tent上提供。

图形离群值检测是一项具有许多应用程序的新兴但至关重要的机器学习任务。尽管近年来算法扩散，但缺乏标准和统一的绩效评估设置限制了它们在现实世界应用中的进步和使用。为了利用差距，我们（据我们所知）（据我们所知）第一个全面的无监督节点离群值检测基准为unod，并带有以下亮点：（1）评估骨架从经典矩阵分解到最新图形神经的骨架的14个方法网络； （2）在现实世界数据集上使用不同类型的注射异常值和自然异常值对方法性能进行基准测试； （3）通过在不同尺度的合成图上使用运行时和GPU存储器使用算法的效率和可扩展性。基于广泛的实验结果的分析，我们讨论了当前渠道方法的利弊，并指出了多个关键和有希望的未来研究方向。

图形存在于许多现实世界中的应用中，例如财务欺诈检测，商业建议和社交网络分析。但是，鉴于图形注释或标记的高成本，我们面临严重的图形标签 - 刻度问题，即，图可能具有一些标记的节点。这样一个问题的一个例子是所谓的\ textit {少数弹性节点分类}。该问题的主要方法均依靠\ textit {情节元学习}。在这项工作中，我们通过提出一个基本问题来挑战现状，元学习是否是对几个弹性节点分类任务的必要条件。我们在标准的几杆节点分类设置下提出了一个新的简单框架，作为学习有效图形编码器的元学习的替代方法。该框架由有监督的图形对比学习以及新颖的数据增强，子图编码和图形上的多尺度对比度组成。在三个基准数据集（Corafull，Reddit，OGBN）上进行的广泛实验表明，新框架显着胜过基于最先进的元学习方法。

图形表示学习引起了极大的关注，因为它在许多现实世界中的表现出色。但是，由于数据标记始终是时间和资源的消耗，因此，特定任务的普遍监督图表学习模型通常会遇到标签稀疏问题。鉴于此，已经提出了将图表表示学习和几乎没有射击学习的优势结合在一起的图形学习（FSLG）（FSLG），以面对有限的注释数据挑战，以解决性能退化。最近有许多研究FSLG的研究。在本文中，我们以一系列方法和应用的形式对这些工作进行了全面的调查。具体而言，我们首先引入FSLG挑战和基础，然后根据不同粒度级别的三个主要图形挖掘任务（即节点，边缘和图形）对FSLG的现有工作进行分类和总结。最后，我们分享了FSLG的一些未来研究方向的想法。在过去的几年中，这项调查的作者对FSLG的AI文献做出了重大贡献。

Graph Contrastive Learning (GCL) has recently drawn much research interest for learning generalizable node representations in a self-supervised manner. In general, the contrastive learning process in GCL is performed on top of the representations learned by a graph neural network (GNN) backbone, which transforms and propagates the node contextual information based on its local neighborhoods. However, nodes sharing similar characteristics may not always be geographically close, which poses a great challenge for unsupervised GCL efforts due to their inherent limitations in capturing such global graph knowledge. In this work, we address their inherent limitations by proposing a simple yet effective framework -- Simple Neural Networks with Structural and Semantic Contrastive Learning} (S^3-CL). Notably, by virtue of the proposed structural and semantic contrastive learning algorithms, even a simple neural network can learn expressive node representations that preserve valuable global structural and semantic patterns. Our experiments demonstrate that the node representations learned by S^3-CL achieve superior performance on different downstream tasks compared with the state-of-the-art unsupervised GCL methods. Implementation and more experimental details are publicly available at \url{https://github.com/kaize0409/S-3-CL.}

图形神经网络是一种强大的深度学习工具，用于建模图形结构化数据，在众多图形学习任务上表现出了出色的性能。为了解决深图学习中的数据噪声和数据稀缺性问题，最近有关图形数据的研究已加剧。但是，常规数据增强方法几乎无法处理具有多模式性的非欧几里得空间中定义的图形结构化数据。在这项调查中，我们正式提出了图数据扩展的问题，并进一步审查了代表性技术及其在不同深度学习问题中的应用。具体而言，我们首先提出了图形数据扩展技术的分类法，然后通过根据增强信息方式对相关工作进行分类，从而提供结构化的审查。此外，我们总结了以数据为中心的深图学习中两个代表性问题中图数据扩展的应用：（1）可靠的图形学习，重点是增强输入图的实用性以及通过图数据增强的模型容量； （2）低资源图学习，其针对通过图数据扩大标记的训练数据量表的目标。对于每个问题，我们还提供层次结构问题分类法，并审查与图数据增强相关的现有文献。最后，我们指出了有希望的研究方向和未来研究的挑战。