一种新的属性图重叠聚类挖掘算法

属性图各节点附有的节点属性标签,为节点提供了更加丰富的信息,在数据挖掘应用,特别是数据聚类问题中如何有效利用这些丰富的信息,已经成为开展此类研究的研究目的.不同于传统图聚类,属性图上的聚类要同时考虑图的结构信息和节点的属性信息,因此如何平衡两者之间的关系,这是属性图聚类主要关注所在.目前已提出的属性图聚类算法,部分算法的效率很高,然而聚类质量较差,同时一些算法可以得到较好的聚类结构,然而算法消耗大量的系统资源,效率也较低.这些算法均没有考虑簇之间存在重叠的情况,这导致无法得到更高精度的聚类结构.因而提出一种属性图上的重叠聚类挖掘算法,实验表明,提出的算法可以得到更高的聚类精度,特别是可以提升聚类内部节点的属性相似度.     

一种高效的属性图聚类方法

图是描述现实世界各类复杂系统的一种普适模型,且许多实际应用中的图是大规模的.图的聚类是理解、分析和可视化大规模图的关键技术之一.现实世界的图往往包含丰富的属性信息,如何综合结构和属性信息进行属性图的聚类是一个新的挑战.大多数的现有方法或者将结构和属性转化为距离,基于传统方法进行聚类;或者只考虑某一方面聚类.文中结合信息论中最小长度原则,基于遗传算法,提出一种高效的属性图聚类方法GA-AGC.通过对属性图聚类问题建模,转化为最小描述长度原则问题;扩展标签传播方法作为遗传算法初始化方法,结合编码减小的局部变异方法,提出一种解决属性图聚类的遗传算法.文中方法无需设定聚类的数目,算法复杂度近似线性于结点和边的数目.真实数据集上的实验验证了算法的有效性和高效性.     

基于节点聚类复杂度的图聚类方法

图聚类可以发现网络中的社区结构，是复杂网络分析中的一项重要任务。针对不同节点的聚类难度各异的问题，提出了一种基于节点聚类复杂度的图聚类算法(Graph Clustering Algorithm Based on Node Clustering Complexity, GCNCC),用于判断节点的聚类复杂度，为聚类复杂度低的节点赋予伪标签，利用伪标签提供的监督信息降低其他节点的聚类复杂度，进而得到网络聚类结果。GCNCC包括节点表示、节点聚类复杂度判别和图聚类3个主要模块。节点表示模块得到保持网络集聚性的表示；节点聚类复杂度判别模块用于判断网络中的低聚类复杂度节点，并利用低聚类复杂度节点的伪标签信息来优化更新网络中其他节点的聚类复杂度；图聚类模块采用标签传播方法，将低聚类复杂度节点标签传播给高聚类复杂度节点，以得到聚类结果。在3个真实的引文网络和3个生物数据集上与9种经典算法进行对比，算法GCNCC在ACC,NMI,ARI和F1等方面均表现良好。     

基于进化聚类的动态网络社团发现

社团的数目和时间平滑性的平衡因子一直是基于进化聚类的动态网络社团发现算法的最大的问题.提出一种基于标签的多目标优化的动态网络社团发现算法（LDMGA）.借鉴多目标遗传算法思想,将进化聚类思想转换为多目标遗传算法优化问题,保证当前时刻的聚类质量的同时,又能使当前聚类结果与前一个时刻网络结构保持一致.该算法在初始化过程加入标签传播算法,增加初始个体的聚类质量.提出基于标签的变异算法,增强了算法的聚类效果和算法的收敛速度.同时,多目标遗传算法和标签算法的结合使算法可扩展性强,运行时间随着节点或者边数目增加呈线性增长.将该算法与目前优秀算法在仿真数据集和真实数据集上进行对比实验,结果表明,该算法既有良好的聚类效果,又有良好的扩展性.     

基于快照的大规模动态图相似节点查询算法

动态图拓扑结构演进过程中,为了量化在一定时间域内节点间联系的变化情况,定义了一种泛相似节点的概念,通过衡量其与当前节点的联系是否频繁、分布是否均匀来确定与当前节点的泛相似程度,并提出了一种基于快照的大规模动态图泛相似节点查询处理算法。具体包括:图动态演进过程的快照集表示,即演进动态图;图动态演进过程中的节点泛相似的语义及其形式化表示方式,从联系的频繁程度与分布的均匀程度对节点的相似程度进行了刻画;节点泛相似语义的矩阵表示及处理方式;针对这种语义的泛相似节点查询处理算法。真实数据集和合成数据集上的实验结果均表明算法能够处理大规模动态图上泛相似节点的查询问题,并在实际应用中运用实现。     

融合拓扑和属性的动态网络链路预测方法

网络数据中出现的大量节点属性和随时间变化的特征,给链路预测提出了新挑战。基于注意力机制和循环神经网络对随时间演化网络进行建模,提出了DTA-LP模型。与传统的静态链路预测算法相比,DTA-LP使用LSTM捕获时序信息,动态预测可以更好应用于现实网络;与基于网络拓扑的动态链路预测算法相比,DTA-LP可以聚集高阶拓扑特征,有效挖掘网络邻域信息;与基于属性网络的动态链路预测算法相比,DTA-LP可以加权融合网络拓扑属性,提高预测精度。在4种真实数据上的实验结果表明,该方法能结合网络已有先验知识,以较高的MAP值来预测未来网络中的边,验证了模型的有效性。     

基于模块度优化的标签传播社区发现算法

标签传播算法（LPA）是一种快速高效的社区发现算法,算法无需社区数量等先验信息,但存在大量随机性,稳定性较差. 为了提高标签传播算法的稳定性,提出了一种改进的标签传播算法（LPAMP）. 该算法分为两个阶段,第一阶段以模块度贪婪为依据,进行节点粗聚类;第二阶段在粗聚类的基础上,进行节点标签传播. 实验结果表明,所提算法降低了标签传播算法的随机性,增强了稳定性,并且提高了准确率.     

图数据发布隐私保护的聚类匿名方法

社交网络中积累的海量信息构成一类图大数据,为防范隐私泄露,一般在发布此类数据时需要做匿名化处理.针对现有匿名方案难以防范同时以结构和属性信息为背景知识的攻击的不足,研究一种基于节点连接结构和属性值的属性图聚类匿名化方法,利用属性图表示社交网络数据,综合根据节点间的结构和属性相似度,将图中所有节点聚类成一些包含节点个数不小于k的超点,特别针对各超点进行匿名化处理.该方法中,超点的子图隐匿和属性概化可以分别防范一切基于结构和属性背景知识的识别攻击.另外,聚类过程平衡了节点间的连接紧密性和属性值相近性,有利于减小结构和属性的总体信息损失值,较好地维持数据的可用性.实验结果表明了该方法在实现算法功能和减少信息损失方面的有效性.     

基于MapReduce的图结构聚类算法

图结构聚类（SCAN）是一种著名的基于密度的图聚类算法。该算法不仅能够找到图中的聚类结构,而且还能发现图中的Hub节点和离群节点。然而,随着图数据规模越来越大,传统的SCAN算法的复杂度为O（m^1.5）（m为图中边的条数）,因此很难处理大规模的图数据。为了解决SCAN算法的可扩展性问题,本文提出了一种新颖的基于MapReduce的海量图结构聚类算法MRSCAN。具体地,我们提出了一种计算核心节点,以及两种合并聚类的MapReduce算法。最后,在多个真实的大规模图数据集上进行实验测试,实验结果验证了算法的准确性、有效性,以及可扩展性。     

密度敏感的半监督谱聚类

聚类通常被认为是一种无监督的数据分析方法,然而在实际问题中可以很容易地获得有限的样本先验信息,如样本的成对限制信息.大量研究表明,在聚类搜索过程中充分利用先验信息会显著提高聚类算法的性能.首先分析了在聚类过程中仅利用成对限制信息存在的不足,尝试探索数据集本身固有的先验信息--空间一致性先验信息,并提出利用这类先验信息的具体方法.接着,将两类先验信息同时引入经典的谱聚类算法中,提出一种密度敏感的半监督谱聚类算法(density-sensitive semi-supervised spectral clustering algorithm,简称DS-SSC).两类先验信息在指导聚类搜索的过程中能够起到相辅相成的作用,这使得DS-SSC算法相对于仅利用成对限制信息的聚类算法在聚类性能上有了显著的提高.在UCI基准数据集、USPS手写体数字集以及TREC的文本数据集上的实验结果验证了这一点.     

Incremental K-clique clustering in dynamic social networks

Clustering entities into dense parts is an important issue in social network analysis. Real social networks usually evolve over time and it remains a problem to efficiently cluster dynamic social networks. In this paper, a dynamic social network is modeled as an initial graph with an infinite change stream, called change stream model, which naturally eliminates the parameter setting problem of snapshot graph model. Based on the change stream model, the incremental version of a well known k-clique clustering problem is studied and incremental k-clique clustering algorithms are proposed based on local DFS (depth first search) forest updating technique. It is theoretically proved that the proposed algorithms outperform corresponding static ones and incremental spectral clustering algorithm in terms of time complexity. The practical performances of our algorithms are extensively evaluated and compared with the baseline algorithms on ENRON and DBLP datasets. Experimental results show that incremental k-clique clustering algorithms are much more efficient than corresponding static ones, and have no accumulating errors that incremental spectral clustering algorithm has and can capture the evolving details of the clusters that snapshot graph model based algorithms miss.     

基于深度神经网络和门控循环单元的动态图表示学习方法

学习图中节点的潜在向量表示是一项重要且普遍存在的任务,旨在捕捉图中节点的各种属性。大量工作证明静态图表示已经能够学习到节点的部分信息,然而,真实世界的图是随着时间的推移而演变的。为了解决多数动态网络算法不能有效保留节点邻域结构和时态信息的问题,提出了基于深度神经网络（DNN）和门控循环单元（GRU）的动态网络表示学习方法DynAEGRU。该方法以自编码器作为框架,其中的编码器首先用DNN聚集邻域信息以得到低维特征向量,然后使用GRU网络提取节点时态信息,最后用解码器重构邻接矩阵并将其与真实图对比来构建损失。通过与几种静态图和动态图表示学习算法在3个数据集上进行实验分析,结果表明DynAEGRU具有较好的性能增益。     

基于元路径的图Transformer神经网络

图神经网络作为一种新的深度学习模型,被广泛运用在图数据中,并极大地推动了推荐系统、社交网络、知识图谱等应用的发展.现有的异构图神经网络通常事先定义了多条元路径来学习异构图中的复合关系.然而,这些模型通常在特征聚合步骤中只考虑单条元路径,导致模型只关注了元路径的局部结构,忽略了元路径之间的全局相关性;还有一些模型则是忽略掉了元路径的中间节点和边信息,导致模型无法学习到元路径内部的语义信息.针对以上问题,本文提出一种基于元路径的图Transformer神经网络(MaGTNN).该模型首先将异构图采样为基于元路径的多关系子图,利用提出的位置编码和边编码的方法来获取元路径中的语义信息.随后使用改进的图Transformer层计算出目标节点与其元邻居的相似度,并利用该相似度来聚合其所有的元邻居信息.在3个公开数据集的节点分类和节点聚类任务中, MaGTNN均高于最新的基准模型.     

A regularized graph layout framework for dynamic network visualization

Many real-world networks, including social and information networks, are dynamic structures that evolve over time. Such dynamic networks are typically visualized using a sequence of static graph layouts. In addition to providing a visual representation of the network structure at each time step, the sequence should preserve the mental map between layouts of consecutive time steps to allow a human to interpret the temporal evolution of the network. In this paper, we propose a framework for dynamic network visualization in the on-line setting where only present and past graph snapshots are available to create the present layout. The proposed framework creates regularized graph layouts by augmenting the cost function of a static graph layout algorithm with a grouping penalty, which discourages nodes from deviating too far from other nodes belonging to the same group, and a temporal penalty, which discourages large node movements between consecutive time steps. The penalties increase the stability of the layout sequence, thus preserving the mental map. We introduce two dynamic layout algorithms within the proposed framework, namely dynamic multidimensional scaling and dynamic graph Laplacian layout. We apply these algorithms on several data sets to illustrate the importance of both grouping and temporal regularization for producing interpretable visualizations of dynamic networks.     

A parallel fuzzy clustering algorithm for large graphs using Pregel

Large graphs are scale free and ubiquitous having irregular relationships. Clustering is used to find existent similar patterns in graphs and thus help in getting useful insights. In real-world, nodes may belong to more than one cluster thus, it is essential to analyze fuzzy cluster membership of nodes. Traditional centralized fuzzy clustering algorithms incur high communication cost and produce poor quality of clusters when used for large graphs. Thus, scalable solutions are obligatory to handle huge amount of data in less computational time with minimum disk access. In this paper, we proposed a parallel fuzzy clustering algorithm named ‘PGFC’ for handling scalable graph data. It will be advantageous from the viewpoint of expert systems to develop a clustering algorithm that can assure scalability along with better quality of clusters for handling large graphs.The algorithm is parallelized using bulk synchronous parallel (BSP) based Pregel model. The cluster centers are initialized using degree centrality measure, resulting in lesser number of iterations. The performance of PGFC is compared with other state of art clustering algorithms using synthetic graphs and real world networks. The experimental results reveal that the proposed PGFC scales up linearly to handle large graphs and produces better quality of clusters when compared to other graph clustering counterparts.     

Matching graphs with unique node labels

A special class of graphs is introduced in this paper. The graphs belonging to this class are characterised by the existence of unique node labels. A number of matching algorithms for graphs with unique node labels are developed. It is shown that problems such as graph isomorphism, subgraph isomorphism, maximum common subgraph (MCS) and graph edit distance (GED) have a computational complexity that is only quadratic in the number of nodes. Moreover, computing the median of a set of graphs is only linear in the cardinality of the set. In a series of experiments, it is demonstrated that the proposed algorithms run very fast in practice. The considered class makes the matching of large graphs, consisting of thousands of nodes, computationally tractable. We also discuss an application of the considered class of graphs and related matching algorithms to the classification and detection of abnormal events in computer networks.     

Toward online node classification on streaming networks

The proliferation of networked data in various disciplines motivates a surge of research interests on network or graph mining. Among them, node classification is a typical learning task that focuses on exploiting the node interactions to infer the missing labels of unlabeled nodes in the network. A vast majority of existing node classification algorithms overwhelmingly focus on static networks and they assume the whole network structure is readily available before performing learning algorithms. However, it is not the case in many real-world scenarios where new nodes and new links are continuously being added in the network. Considering the streaming nature of networks, we study how to perform online node classification on this kind of streaming networks (a.k.a. online learning on streaming networks). As the existence of noisy links may negatively affect the node classification performance, we first present an online network embedding algorithm to alleviate this problem by obtaining the embedding representation of new nodes on the fly. Then we feed the learned embedding representation into a novel online soft margin kernel learning algorithm to predict the node labels in a sequential manner. Theoretical analysis is presented to show the superiority of the proposed framework of online learning on streaming networks (OLSN). Extensive experiments on real-world networks further demonstrate the effectiveness and efficiency of the proposed OLSN framework.     

Efficient computation of distance labeling for decremental updates in large dynamic graphs

Since today’s real-world graphs, such as social network graphs, are evolving all the time, it is of great importance to perform graph computations and analysis in these dynamic graphs. Due to the fact that many applications such as social network link analysis with the existence of inactive users need to handle failed links or nodes, decremental computation and maintenance for graphs is considered a challenging problem. Shortest path computation is one of the most fundamental operations for managing and analyzing large graphs. A number of indexing methods have been proposed to answer distance queries in static graphs. Unfortunately, there is little work on answering such queries for dynamic graphs. In this paper, we focus on the problem of computing the shortest path distance in dynamic graphs, particularly on decremental updates (i.e., edge deletions). We propose maintenance algorithms based on distance labeling, which can handle decremental updates efficiently. By exploiting properties of distance labeling in original graphs, we are able to efficiently maintain distance labeling for new graphs. We experimentally evaluate our algorithms using eleven real-world large graphs and confirm the effectiveness and efficiency of our approach. More specifically, our method can speed up index re-computation by up to an order of magnitude compared with the state-of-the-art method, Pruned Landmark Labeling (PLL).     

图网络层级信息挖掘分类算法综述

深度学习作为人工智能的一个研究分支发展迅速,而研究数据主要是语音、图像和视频等,这些具有规则结构的数据通常在欧氏空间中表示。然而许多学习任务需要处理的数据是从非欧氏空间中生成,这些数据特征和其关系结构可以用图来定义。图卷积神经网络通过将卷积定理应用于图,完成节点之间的信息传播与聚合,成为建模图数据一种有效的方法。尽管图卷积神经网络取得了巨大成功,但针对图任务中的节点分类问题,由于深层图结构优化的特有难点——过平滑现象,现有的多数模型都只有两三层的浅层模型架构。在理论上,图卷积神经网络的深层结构可以获得更多节点表征信息,因此针对其层级信息进行研究,将层级结构算法迁移到图数据分析的核心在于图层级卷积算子构建和图层级间信息融合。本文对图网络层级信息挖掘算法进行综述,介绍图神经网络的发展背景、存在问题以及图卷积神经网络层级结构算法的发展,根据不同图卷积层级信息处理将现有算法分为正则化方法和架构调整方法。正则化方法通过重新构建图卷积算子更好地聚合邻域信息,而架构调整方法则融合层级信息丰富节点表征。图卷积神经网络层级特性实验表明,图结构中存在层级特性节点,现有图层级信息挖掘算法仍未对层级特性节点的...     

Active exploration for large graphs

Modern information networks, such as social networks, communication networks, and citation networks, are often characterized by very large sizes and dynamically changing structures. Common solutions to graph mining tasks (e.g., node classification) usually employ an unrestricted sampling-then-mining paradigm to reduce a large network to a manageable size, followed by subsequent mining tasks. However, real-world networks may be unaccessible at once and must be crawled progressively. This can be due to the fact that the size of the network is too large, or some privacy/legal concerns. In this paper, we propose an Active Exploration framework for large graphs, where the goal is to simultaneously carry out network sampling and node labeling in order to build a sampled network from which the trained classifier can have the maximum node classification accuracy. To achieve this goal, we consider a network as a Markov chain and compute the stationary distribution of the nodes by deriving supervised random walks. The stationary distribution helps identify specific nodes to be sampled in the next step, and the labeling process labels the most informative node which in turn strengthens the sampling of the network. To improve the scalability of active exploration for large graphs, we also propose a more efficient multi-seed algorithm that simultaneously runs multiple, parallel exploration processes, and makes joint decisions to determine which nodes are to be sampled and labeled next. The simultaneous, mutually enhanced sampling and labeling processes ensure that the final sampled network contains a maximum number of nodes directly related to the underlying mining tasks. Experiments on both synthetic and real-world networks demonstrate that our active exploration algorithms have much better chance to include target nodes in the sampled networks than baseline methods.