Synthetic data generation has recently gained widespread attention as a more reliable alternative to traditional data anonymization. The involved methods are originally developed for image synthesis. Hence, their application to the typically tabular and relational datasets from healthcare, finance and other industries is non-trivial. While substantial research has been devoted to the generation of realistic tabular datasets, the study of synthetic relational databases is still in its infancy. In this paper, we combine the variational autoencoder framework with graph neural networks to generate realistic synthetic relational databases. We then apply the obtained method to two publicly available databases in computational experiments. The results indicate that real databases' structures are accurately preserved in the resulting synthetic datasets, even for large datasets with advanced data types.

Pre-publication draft of a book to be published byMorgan & Claypool publishers. Unedited version released with permission. All relevant copyrights held by the author and publisher extend to this pre-publication draft.

In data-driven systems, data exploration is imperative for making real-time decisions. However, big data is stored in massive databases that are difficult to retrieve. Approximate Query Processing (AQP) is a technique for providing approximate answers to aggregate queries based on a summary of the data (synopsis) that closely replicates the behavior of the actual data, which can be useful where an approximate answer to the queries would be acceptable in a fraction of the real execution time. In this paper, we discuss the use of Generative Adversarial Networks (GANs) for generating tabular data that can be employed in AQP for synopsis construction. We first discuss the challenges associated with constructing synopses in relational databases and then introduce solutions to those challenges. Following that, we organized statistical metrics to evaluate the quality of the generated synopses. We conclude that tabular data complexity makes it difficult for algorithms to understand relational database semantics during training, and improved versions of tabular GANs are capable of constructing synopses to revolutionize data-driven decision-making systems.

图表神经网络（GNNS）最近在人工智能（AI）领域的普及，这是由于它们作为输入数据相对非结构化数据类型的独特能力。尽管GNN架构的一些元素在概念上类似于传统神经网络（以及神经网络变体）的操作中，但是其他元件代表了传统深度学习技术的偏离。本教程通过整理和呈现有关GNN最常见和性能变种的动机，概念，数学和应用的细节，将GNN的权力和新颖性暴露给AI从业者。重要的是，我们简明扼要地向实际示例提出了本教程，从而为GNN的主题提供了实用和可访问的教程。

在本文中，我们提出了多分辨率的等级图变分性Autiachoders（MGVAE），第一层级生成模型以多分辨率和等分的方式学习和生成图。在每个分辨率级别，MGVAE采用更高的顺序消息，以便在学习中对图进行编码，同时学习将其分配到互斥的集群中并赋予最终产生潜在分布的层次结构的较低分辨率。然后，MGVAE构造分层生成模型以改变地解码成粗糙的图形的层次。重要的是，我们提出的框架是关于节点排序的端到端排列等级。MGVAE通过多种生成任务实现竞争结果，包括一般图生成，分子产生，无监督的分子表示学习，以预测分子特性，引用图的链路预测，以及基于图的图像生成。

Graph神经网络（GNN）最近已成为使用图的机器学习的主要范式。对GNNS的研究主要集中于消息传递神经网络（MPNNS）的家族。与同构的Weisfeiler-Leman（WL）测试类似，这些模型遵循迭代的邻域聚合过程以更新顶点表示，并通过汇总顶点表示来更新顶点图表。尽管非常成功，但在过去的几年中，对MPNN进行了深入的研究。因此，需要新颖的体系结构，这将使该领域的研究能够脱离MPNN。在本文中，我们提出了一个新的图形神经网络模型，即所谓的$ \ pi $ -gnn，该模型学习了每个图的“软”排列（即双随机）矩阵，从而将所有图形投影到一个共同的矢量空间中。学到的矩阵在输入图的顶点上强加了“软”顺序，并基于此顺序，将邻接矩阵映射到向量中。这些向量可以被送入完全连接或卷积的层，以应对监督的学习任务。在大图的情况下，为了使模型在运行时间和记忆方面更有效，我们进一步放松了双随机矩阵，以使其排列随机矩阵。我们从经验上评估了图形分类和图形回归数据集的模型，并表明它与最新模型达到了性能竞争。

即使机器学习算法已经在数据科学中发挥了重要作用，但许多当前方法对输入数据提出了不现实的假设。由于不兼容的数据格式，或数据集中的异质，分层或完全缺少的数据片段，因此很难应用此类方法。作为解决方案，我们提出了一个用于样本表示，模型定义和培训的多功能，统一的框架，称为“ Hmill”。我们深入审查框架构建和扩展的机器学习的多个范围范式。从理论上讲，为HMILL的关键组件的设计合理，我们将通用近似定理的扩展显示到框架中实现的模型所实现的所有功能的集合。本文还包含有关我们实施中技术和绩效改进的详细讨论，该讨论将在MIT许可下发布供下载。该框架的主要资产是其灵活性，它可以通过相同的工具对不同的现实世界数据源进行建模。除了单独观察到每个对象的一组属性的标准设置外，我们解释了如何在框架中实现表示整个对象系统的图表中的消息推断。为了支持我们的主张，我们使用框架解决了网络安全域的三个不同问题。第一种用例涉及来自原始网络观察结果的IoT设备识别。在第二个问题中，我们研究了如何使用以有向图表示的操作系统的快照可以对恶意二进制文件进行分类。最后提供的示例是通过网络中实体之间建模域黑名单扩展的任务。在所有三个问题中，基于建议的框架的解决方案可实现与专业方法相当的性能。

International initiatives such as METABRIC (Molecular Taxonomy of Breast Cancer International Consortium) have collected several multigenomic and clinical data sets to identify the undergoing molecular processes taking place throughout the evolution of various cancers. Numerous Machine Learning and statistical models have been designed and trained to analyze these types of data independently, however, the integration of such differently shaped and sourced information streams has not been extensively studied. To better integrate these data sets and generate meaningful representations that can ultimately be leveraged for cancer detection tasks could lead to giving well-suited treatments to patients. Hence, we propose a novel learning pipeline comprising three steps - the integration of cancer data modalities as graphs, followed by the application of Graph Neural Networks in an unsupervised setting to generate lower-dimensional embeddings from the combined data, and finally feeding the new representations on a cancer sub-type classification model for evaluation. The graph construction algorithms are described in-depth as METABRIC does not store relationships between the patient modalities, with a discussion of their influence over the quality of the generated embeddings. We also present the models used to generate the lower-latent space representations: Graph Neural Networks, Variational Graph Autoencoders and Deep Graph Infomax. In parallel, the pipeline is tested on a synthetic dataset to demonstrate that the characteristics of the underlying data, such as homophily levels, greatly influence the performance of the pipeline, which ranges between 51\% to 98\% accuracy on artificial data, and 13\% and 80\% on METABRIC. This project has the potential to improve cancer data understanding and encourages the transition of regular data sets to graph-shaped data.

数据质量是发展医疗保健中值得信赖的AI的关键因素。大量具有控制混杂因素的策划数据集可以帮助提高下游AI算法的准确性，鲁棒性和隐私性。但是，访问高质量的数据集受数据获取的技术难度的限制，并且严格的道德限制阻碍了医疗保健数据的大规模共享。数据合成算法生成具有与真实临床数据相似的分布的数据，可以作为解决可信度AI的发展过程中缺乏优质数据的潜在解决方案。然而，最新的数据合成算法，尤其是深度学习算法，更多地集中于成像数据，同时忽略了非成像医疗保健数据的综合，包括临床测量，医疗信号和波形以及电子保健记录（EHRS）（EHRS） 。因此，在本文中，我们将回顾合成算法，尤其是对于非成像医学数据，目的是在该领域提供可信赖的AI。本教程风格的审查论文将对包括算法，评估，局限性和未来研究方向在内的各个方面进行全面描述。

Counterfactual explanations promote explainability in machine learning models by answering the question "how should an input instance be perturbed to obtain a desired predicted label?". The comparison of this instance before and after perturbation can enhance human interpretation. Most existing studies on counterfactual explanations are limited in tabular data or image data. In this work, we study the problem of counterfactual explanation generation on graphs. A few studies have explored counterfactual explanations on graphs, but many challenges of this problem are still not well-addressed: 1) optimizing in the discrete and disorganized space of graphs; 2) generalizing on unseen graphs; and 3) maintaining the causality in the generated counterfactuals without prior knowledge of the causal model. To tackle these challenges, we propose a novel framework CLEAR which aims to generate counterfactual explanations on graphs for graph-level prediction models. Specifically, CLEAR leverages a graph variational autoencoder based mechanism to facilitate its optimization and generalization, and promotes causality by leveraging an auxiliary variable to better identify the underlying causal model. Extensive experiments on both synthetic and real-world graphs validate the superiority of CLEAR over the state-of-the-art methods in different aspects.

Machine learning on graphs is an important and ubiquitous task with applications ranging from drug design to friendship recommendation in social networks. The primary challenge in this domain is finding a way to represent, or encode, graph structure so that it can be easily exploited by machine learning models. Traditionally, machine learning approaches relied on user-defined heuristics to extract features encoding structural information about a graph (e.g., degree statistics or kernel functions). However, recent years have seen a surge in approaches that automatically learn to encode graph structure into low-dimensional embeddings, using techniques based on deep learning and nonlinear dimensionality reduction. Here we provide a conceptual review of key advancements in this area of representation learning on graphs, including matrix factorization-based methods, random-walk based algorithms, and graph neural networks. We review methods to embed individual nodes as well as approaches to embed entire (sub)graphs. In doing so, we develop a unified framework to describe these recent approaches, and we highlight a number of important applications and directions for future work.

检测欺诈性交易是控制​​电子商务市场风险的重要组成部分。除了已经在生产中部署的基于规则和机器学习过滤器外，我们还希望使用图形神经网络（GNN）进行有效的实时推理，这对于在事务图中捕获多跃风风险传播非常有用。但是，在生产中实施GNN时出现了两个挑战。首先，在消息传递中不应考虑以预测过去中的动态图中的未来信息。其次，图形查询和GNN模型推断的延迟通常高达数百毫秒，这对于某些关键的在线服务来说是昂贵的。为了应对这些挑战，我们提出了一个批处理和实时的成立图拓扑（BRIGHT）框架，以进行端到端的GNN学习，以允许有效的在线实时推理。 Bright框架由图形转换模块（两阶段有向图）和相应的GNN体系结构（Lambda神经网络）组成。两阶段的指示图保证了通过邻居传递的信息仅来自历史支付交易。它分别由代表历史关系和实时链接的两个子图组成。 Lambda神经网络将推断分为两个阶段：实体嵌入的批次推断和交易预测的实时推断。我们的实验表明，在平均W.R.T.〜精确度中，BRIGHT优于基线模型> 2 \％。此外，BRIGHT在实时欺诈检测上在计算上是有效的。关于端到端性能（包括邻居查询和推理），BRIGHT可以将P99延迟降低> 75 \％。对于推理阶段，与传统GNN相比，我们的加速平均为7.8美元。

Outstanding achievements of graph neural networks for spatiotemporal time series analysis show that relational constraints introduce an effective inductive bias into neural forecasting architectures. Often, however, the relational information characterizing the underlying data-generating process is unavailable and the practitioner is left with the problem of inferring from data which relational graph to use in the subsequent processing stages. We propose novel, principled - yet practical - probabilistic score-based methods that learn the relational dependencies as distributions over graphs while maximizing end-to-end the performance at task. The proposed graph learning framework is based on consolidated variance reduction techniques for Monte Carlo score-based gradient estimation, is theoretically grounded, and, as we show, effective in practice. In this paper, we focus on the time series forecasting problem and show that, by tailoring the gradient estimators to the graph learning problem, we are able to achieve state-of-the-art performance while controlling the sparsity of the learned graph and the computational scalability. We empirically assess the effectiveness of the proposed method on synthetic and real-world benchmarks, showing that the proposed solution can be used as a stand-alone graph identification procedure as well as a graph learning component of an end-to-end forecasting architecture.

Knowledge graphs enable a wide variety of applications, including question answering and information retrieval. Despite the great effort invested in their creation and maintenance, even the largest (e.g., Yago, DBPedia or Wikidata) remain incomplete. We introduce Relational Graph Convolutional Networks (R-GCNs) and apply them to two standard knowledge base completion tasks: Link prediction (recovery of missing facts, i.e. subject-predicate-object triples) and entity classification (recovery of missing entity attributes). R-GCNs are related to a recent class of neural networks operating on graphs, and are developed specifically to deal with the highly multi-relational data characteristic of realistic knowledge bases. We demonstrate the effectiveness of R-GCNs as a stand-alone model for entity classification. We further show that factorization models for link prediction such as DistMult can be significantly improved by enriching them with an encoder model to accumulate evidence over multiple inference steps in the relational graph, demonstrating a large improvement of 29.8% on FB15k-237 over a decoder-only baseline. * Equal contribution.

在过去十年中，图形内核引起了很多关注，并在结构化数据上发展成为一种快速发展的学习分支。在过去的20年中，该领域发生的相当大的研究活动导致开发数十个图形内核，每个图形内核都对焦于图形的特定结构性质。图形内核已成功地成功地在广泛的域中，从社交网络到生物信息学。本调查的目标是提供图形内核的文献的统一视图。特别是，我们概述了各种图形内核。此外，我们对公共数据集的几个内核进行了实验评估，并提供了比较研究。最后，我们讨论图形内核的关键应用，并概述了一些仍有待解决的挑战。

最近，图形神经网络（GNN）显着提高了图形上机器学习任务的性能。但是，这一技术突破使人们感到奇怪：GNN如何做出这样的决定，我们可以高度信心信任它的预测吗？当涉及到一些关键领域（例如生物医学）时，做出错误的决策可能会产生严重的后果，在应用它们之前解释GNN的内部工作机制至关重要。在本文中，我们为遵循消息传递方案GnnInterPreter的不同GNN的新型模型模型级解释方法提出了一种新颖的模型级解释方法，以解释GNN模型的高级决策过程。更具体地说，通过图形的连续放松和重新聚集技巧，GnnInterPreter学习了概率生成图分布，该分布在GNN模型的眼中生成了目标预测的最具代表性图。与唯一的现有作品相比，GnnInterPreter在生成具有不同类型的节点功能和边缘功能的解释图时更加有效，更灵活，而无需引入另一个Blackbox来解释GNN，而无需特定领域的知识。此外，在四个不同数据集上进行的实验研究表明，当模型是理想的情况下，GnnInterPreter生成的解释图可以匹配所需的图形模式，并揭示了如果存在任何模型。

医疗数据集通常由噪声和缺失数据损坏。这些缺失的模式通常被认为是完全随机的，而是在医学场景中，现实是，这些模式由于在一些时间或数据被收集的不alaled的不均匀方式中被收集的传感器而发生突发。本文建议使用异构数据类型和使用顺序变化自动码器（VAES）来模拟医疗数据记录和突发的缺失数据。特别是，我们提出了一种新的方法，SHI-VAE，其扩展了VAE的能力，使VAE的顺序数据流缺失了观察。我们将我们的模型与精密护理单元数据库（ICU）中的最先进的解决方案进行比较和被动人类监测的数据集。此外，我们发现诸如RMSE的标准错误指标不能得出足够的决定性，以评估时间模型，并包括在我们分析地面真理和算中信号之间的互相关。我们表明Shi-VAE在使用两个指标方面实现了最佳性能，而不是GP-VAE模型的计算复杂性较低，这是用于医疗记录的最先进的方法。

Deep learning has revolutionized many machine learning tasks in recent years, ranging from image classification and video processing to speech recognition and natural language understanding. The data in these tasks are typically represented in the Euclidean space. However, there is an increasing number of applications where data are generated from non-Euclidean domains and are represented as graphs with complex relationships and interdependency between objects. The complexity of graph data has imposed significant challenges on existing machine learning algorithms. Recently, many studies on extending deep learning approaches for graph data have emerged. In this survey, we provide a comprehensive overview of graph neural networks (GNNs) in data mining and machine learning fields. We propose a new taxonomy to divide the state-of-the-art graph neural networks into four categories, namely recurrent graph neural networks, convolutional graph neural networks, graph autoencoders, and spatial-temporal graph neural networks. We further discuss the applications of graph neural networks across various domains and summarize the open source codes, benchmark data sets, and model evaluation of graph neural networks. Finally, we propose potential research directions in this rapidly growing field.

理想的合成人群，这是基于活动模型的关键输入，模仿了实际人群中个体和家庭水平属性的分布。由于整个人群的属性通常不可用，因此使用家庭旅行调查（HTS）样本进行人口综合。通过直接从HTS取样来合成种群，忽略了HTS样本中未观察到但存在于种群中的属性组合，称为“采样零”。深层生成模型（DGM）可以潜在地合成采样零，但要产生“结构零”（即，人口中不存在的属性组合）。这项研究提出了一种新的方法，可以在保留采样零的同时最小化结构零。设计了两个正规化，以自定义DGM的培训，并应用于生成的对抗网络（GAN）和变异自动编码器（VAE）。所采用的合成人群可行性和多样性的指标表明产生采样和结构零的能力 - 较低的结构零和较低的采样零表明可行性和较低的多样性。结果表明，所提出的正规化可实现与传统模型相比，合成人群的可行性和多样性的可观绩效。拟议的VAE还以79.2％的精度（即20.8％的结构零速率）产生了23.5％的人口，而拟议的GAN产生了18.3％的忽视人群，精度为89.0％。拟议的DGM改进会产生更可行和多样化的合成人群，这对于基于活动的模型的准确性至关重要。

多跳跃逻辑推理是在知识图（KGS）上学习领域的一个已建立问题。它涵盖了单跳连接预测以及其他更复杂的逻辑查询类型。现有的算法仅在经典的三重基图上运行，而现代KG经常采用超相关的建模范式。在此范式中，键入的边缘可能具有几对键值对，称为限定符，可为事实提供细粒度的环境。在查询中，此上下文修改了关系的含义，通常会减少答案集。经常在现实世界中的应用程序中观察到超相关的查询，并且现有的近似查询答案方法无法使用预选赛对。在这项工作中，我们弥合了这一差距，并将多跳的推理问题扩展到了超级关系的KG，允许解决这一新类型的复杂查询。在图形神经网络和查询嵌入技术的最新进展之下，我们研究了如何嵌入和回答超相关的连词查询。除此之外，我们还提出了一种回答此类查询并在我们的实验中证明的方法，即预选赛可以改善对各种查询模式的查询回答。