Search Results for author: Leman Akoglu

Found 50 papers, 27 papers with code

End-To-End Self-tuning Self-supervised Time Series Anomaly Detection

no code implementations3 Apr 2024 Boje Deforce, Meng-Chieh Lee, Bart Baesens, Estefanía Serral Asensio, Jaemin Yoo, Leman Akoglu

A two-fold challenge for TSAD is a versatile and unsupervised model that can detect various different types of time series anomalies (spikes, discontinuities, trend shifts, etc.)

Anomaly Detection Data Augmentation +2

On the Detection of Reviewer-Author Collusion Rings From Paper Bidding

1 code implementation12 Feb 2024 Steven Jecmen, Nihar B. Shah, Fei Fang, Leman Akoglu

A major threat to the peer-review systems of computer science conferences is the existence of "collusion rings" between reviewers.

Fraud Detection text similarity

Descriptive Kernel Convolution Network with Improved Random Walk Kernel

1 code implementation8 Feb 2024 Meng-Chieh Lee, Lingxiao Zhao, Leman Akoglu

In this paper, we first revisit the RWK and its current usage in KCNs, revealing several shortcomings of the existing designs, and propose an improved graph kernel RWK+, by introducing color-matching random walks and deriving its efficient computation.

Descriptive Feature Engineering +1

Pard: Permutation-Invariant Autoregressive Diffusion for Graph Generation

no code implementations6 Feb 2024 Lingxiao Zhao, Xueying Ding, Leman Akoglu

Current graph diffusion models generate graphs in a one-shot fashion, but they require extra features and thousands of denoising steps to achieve optimal performance.

Denoising Graph Generation

Improving and Unifying Discrete&Continuous-time Discrete Denoising Diffusion

1 code implementation6 Feb 2024 Lingxiao Zhao, Xueying Ding, Lijun Yu, Leman Akoglu

Discrete diffusion models have seen a surge of attention with applications on naturally discrete data such as language and graphs.

Denoising

ADAMM: Anomaly Detection of Attributed Multi-graphs with Metadata: A Unified Neural Network Approach

1 code implementation13 Nov 2023 Konstantinos Sotiropoulos, Lingxiao Zhao, Pierre Jinghong Liang, Leman Akoglu

Given a complex graph database of node- and edge-attributed multi-graphs as well as associated metadata for each graph, how can we spot the anomalous instances?

Representation Learning Unsupervised Anomaly Detection

Self-Supervision for Tackling Unsupervised Anomaly Detection: Pitfalls and Opportunities

no code implementations28 Aug 2023 Leman Akoglu, Jaemin Yoo

Self-supervised learning (SSL) is a growing torrent that has recently transformed machine learning and its many real world applications, by learning on massive amounts of unlabeled data via self-generated supervisory signals.

Data Augmentation Density Estimation +3

Fast Unsupervised Deep Outlier Model Selection with Hypernetworks

no code implementations20 Jul 2023 Xueying Ding, Yue Zhao, Leman Akoglu

Outlier detection (OD) finds many applications with a rich literature of numerous techniques.

Meta-Learning Model Selection +1

DSV: An Alignment Validation Loss for Self-supervised Outlier Model Selection

1 code implementation13 Jul 2023 Jaemin Yoo, Yue Zhao, Lingxiao Zhao, Leman Akoglu

DSV captures the alignment between an augmentation function and the anomaly-generating mechanism with surrogate losses, which approximate the discordance and separability of test data, respectively.

Data Augmentation Model Selection +2

End-to-End Augmentation Hyperparameter Tuning for Self-Supervised Anomaly Detection

no code implementations21 Jun 2023 Jaemin Yoo, Lingxiao Zhao, Leman Akoglu

The first is a new unsupervised validation loss that quantifies the alignment between the augmented training data and the (unlabeled) test data.

Data Augmentation Self-Supervised Anomaly Detection +2

From Explanation to Action: An End-to-End Human-in-the-loop Framework for Anomaly Reasoning and Management

no code implementations6 Apr 2023 Xueying Ding, Nikita Seleznev, Senthil Kumar, C. Bayan Bruss, Leman Akoglu

Anomalies are often indicators of malfunction or inefficiency in various systems such as manufacturing, healthcare, finance, surveillance, to name a few.

Anomaly Detection Management

Unsupervised Machine Learning for Explainable Health Care Fraud Detection

no code implementations5 Nov 2022 Shubhranshu Shekhar, Jetson Leder-Luis, Leman Akoglu

The US federal government spends more than a trillion dollars per year on health care, largely provided by private third parties and reimbursed by the government.

Fraud Detection

Toward Unsupervised Outlier Model Selection

1 code implementation3 Nov 2022 Yue Zhao, Sean Zhang, Leman Akoglu

At its core, ELECT is based on meta-learning; transferring prior knowledge (e. g. model performance) on historical datasets that are similar to the new one to facilitate UOMS.

Meta-Learning Model Selection +1

A Practical, Progressively-Expressive GNN

1 code implementation18 Oct 2022 Lingxiao Zhao, Louis Härtel, Neil Shah, Leman Akoglu

Our model is practical and progressively-expressive, increasing in power with k and c. We demonstrate effectiveness on several benchmark datasets, achieving several state-of-the-art results with runtime and memory usage applicable to practical graphs.

Graph Learning Isomorphism Testing

Graph Anomaly Detection with Unsupervised GNNs

1 code implementation18 Oct 2022 Lingxiao Zhao, Saurabh Sawlani, Arvind Srinivasan, Leman Akoglu

This work aims to fill two gaps in the literature: We (1) design GLAM, an end-to-end graph-level anomaly detection model based on GNNs, and (2) focus on unsupervised model selection, which is notoriously hard due to lack of any labels, yet especially critical for deep NN based models with a long list of hyper-parameters.

Graph Anomaly Detection Model Selection

D.MCA: Outlier Detection with Explicit Micro-Cluster Assignments

1 code implementation15 Oct 2022 Shuli Jiang, Robson Leonardo Ferreira Cordeiro, Leman Akoglu

How can we perform both tasks in-house, i. e., without any post-hoc processing, so that both detection and assignment can benefit simultaneously from each other?

Clustering Outlier Detection

Hyperparameter Optimization for Unsupervised Outlier Detection

no code implementations24 Aug 2022 Yue Zhao, Leman Akoglu

Given an unsupervised outlier detection (OD) algorithm, how can we optimize its hyperparameter(s) (HP) on a new dataset, without any labels?

Hyperparameter Optimization Meta-Learning +1

Data Augmentation is a Hyperparameter: Cherry-picked Self-Supervision for Unsupervised Anomaly Detection is Creating the Illusion of Success

1 code implementation16 Aug 2022 Jaemin Yoo, Tiancheng Zhao, Leman Akoglu

Self-supervised learning (SSL) has emerged as a promising alternative to create supervisory signals to real-world problems, avoiding the extensive cost of manual labeling.

Data Augmentation Self-Supervised Anomaly Detection +2

Automatic Unsupervised Outlier Model Selection

no code implementations NeurIPS 2021 Yue Zhao, Ryan Rossi, Leman Akoglu

Given an unsupervised outlier detection task on a new dataset, how can we automatically select a good outlier detection algorithm and its hyperparameter(s) (collectively called a model)?

Meta-Learning Model Selection +1

Benefit-aware Early Prediction of Health Outcomes on Multivariate EEG Time Series

no code implementations11 Nov 2021 Shubhranshu Shekhar, Dhivya Eswaran, Bryan Hooi, Jonathan Elmer, Christos Faloutsos, Leman Akoglu

Given a cardiac-arrest patient being monitored in the ICU (intensive care unit) for brain activity, how can we predict their health outcomes as early as possible?

Decision Making EEG +2

C-AllOut: Catching & Calling Outliers by Type

no code implementations13 Oct 2021 Guilherme D. F. Silva, Leman Akoglu, Robson L. F. Cordeiro

It is parameter-free and scalable, besides working only with pairwise similarities (or distances) when it is needed.

Outlier Detection TAG +1

Fast Attributed Graph Embedding via Density of States

1 code implementation11 Oct 2021 Saurabh Sawlani, Lingxiao Zhao, Leman Akoglu

We propose A-DOGE, for Attributed DOS-based Graph Embedding, based on density of states (DOS, a. k. a.

Attribute Graph Classification +2

From Stars to Subgraphs: Uplifting Any GNN with Local Structure Awareness

2 code implementations ICLR 2022 Lingxiao Zhao, Wei Jin, Leman Akoglu, Neil Shah

We choose the subgraph encoder to be a GNN (mainly MPNNs, considering scalability) to design a general framework that serves as a wrapper to up-lift any GNN.

Connecting Graph Convolution and Graph PCA

no code implementations29 Sep 2021 Lingxiao Zhao, Leman Akoglu

Based on this connection, the GCN architecture, shaped by stacking graph convolution layers, shares a close relationship with stacking GPCA.

Node Classification

A Comprehensive Survey on Graph Anomaly Detection with Deep Learning

1 code implementation14 Jun 2021 Xiaoxiao Ma, Jia Wu, Shan Xue, Jian Yang, Chuan Zhou, Quan Z. Sheng, Hui Xiong, Leman Akoglu

In this survey, we aim to provide a systematic and comprehensive review of the contemporary deep learning techniques for graph anomaly detection.

Graph Anomaly Detection

Anomaly Mining -- Past, Present and Future

no code implementations21 May 2021 Leman Akoglu

Anomaly mining is an important problem that finds numerous applications in various real world domains such as environmental monitoring, cybersecurity, finance, healthcare and medicine, to name a few.

A Large-scale Study on Unsupervised Outlier Model Selection: Do Internal Strategies Suffice?

1 code implementation3 Apr 2021 Martin Q. Ma, Yue Zhao, Xiaorong Zhang, Leman Akoglu

These so-called internal strategies solely rely on the input data (without labels) and the output (outlier scores) of the candidate models.

Model Selection Outlier Detection

On Using Classification Datasets to Evaluate Graph-Level Outlier Detection: Peculiar Observations and New Insights

1 code implementation23 Dec 2020 Lingxiao Zhao, Leman Akoglu

We carefully study the graph embedding space produced by propagation based models and find two driving factors: (1) disparity between within-class densities which is amplified by propagation, and (2)overlapping support (mixing of embeddings) across classes.

Binary Classification General Classification +3

FairOD: Fairness-aware Outlier Detection

1 code implementation5 Dec 2020 Shubhranshu Shekhar, Neil Shah, Leman Akoglu

Fairness and Outlier Detection (OD) are closely related, as it is exactly the goal of OD to spot rare, minority samples in a given population.

Fairness Outlier Detection

AutoAudit: Mining Accounting and Time-Evolving Graphs

1 code implementation1 Nov 2020 Meng-Chieh Lee, Yue Zhao, Aluna Wang, Pierre Jinghong Liang, Leman Akoglu, Vincent S. Tseng, Christos Faloutsos

How can we spot money laundering in large-scale graph-like accounting datasets?

Social and Information Networks

Anomaly Detection in Large Labeled Multi-Graph Databases

no code implementations7 Oct 2020 Hung T. Nguyen, Pierre J. Liang, Leman Akoglu

Within a large database G containing graphs with labeled nodes and directed, multi-edges; how can we detect the anomalous graphs?

Anomaly Detection

Automating Outlier Detection via Meta-Learning

1 code implementation22 Sep 2020 Yue Zhao, Ryan A. Rossi, Leman Akoglu

Given an unsupervised outlier detection (OD) task on a new dataset, how can we automatically select a good outlier detection method and its hyperparameter(s) (collectively called a model)?

Anomaly Detection AutoML +3

Connecting Graph Convolutional Networks and Graph-Regularized PCA

no code implementations22 Jun 2020 Lingxiao Zhao, Leman Akoglu

Based on this connection, GCN architecture, shaped by stacking graph convolution layers, shares a close relationship with stacking GPCA.

Node Classification

Beyond Homophily in Graph Neural Networks: Current Limitations and Effective Designs

4 code implementations NeurIPS 2020 Jiong Zhu, Yujun Yan, Lingxiao Zhao, Mark Heimann, Leman Akoglu, Danai Koutra

We investigate the representation power of graph neural networks in the semi-supervised node classification task under heterophily or low homophily, i. e., in networks where connected nodes may have different class labels and dissimilar features.

Node Classification on Non-Homophilic (Heterophilic) Graphs

SUOD: Accelerating Large-Scale Unsupervised Heterogeneous Outlier Detection

1 code implementation11 Mar 2020 Yue Zhao, Xiyang Hu, Cheng Cheng, Cong Wang, Changlin Wan, Wen Wang, Jianing Yang, Haoping Bai, Zheng Li, Cao Xiao, Yunlong Wang, Zhi Qiao, Jimeng Sun, Leman Akoglu

Outlier detection (OD) is a key machine learning (ML) task for identifying abnormal objects from general samples with numerous high-stake applications including fraud detection and intrusion detection.

Dimensionality Reduction Fraud Detection +2

Coverage-based Outlier Explanation

no code implementations6 Nov 2019 Yue Wu, Leman Akoglu, Ian Davidson

Existing algorithms are primarily focused on detection, that is the identification of outliers in a given dataset.

Outlier Detection

PairNorm: Tackling Oversmoothing in GNNs

1 code implementation ICLR 2020 Lingxiao Zhao, Leman Akoglu

The performance of graph neural nets (GNNs) is known to gradually decrease with increasing number of layers.

Statistical Analysis of Nearest Neighbor Methods for Anomaly Detection

1 code implementation NeurIPS 2019 Xiaoyi Gu, Leman Akoglu, Alessandro Rinaldo

Nearest-neighbor (NN) procedures are well studied and widely used in both supervised and unsupervised learning problems.

Anomaly Detection

Continual Rare-Class Recognition with Emerging Novel Subclasses

1 code implementation28 Jun 2019 Hung Nguyen, Xuejian Wang, Leman Akoglu

We introduce RaRecognize, which (i) estimates a general decision boundary between the rare and the majority class, (ii) learns to recognize individual rare subclasses that exist within the training data, as well as (iii) flags instances from previously unseen rare subclasses as newly emerging.

Incorporating Privileged Information to Unsupervised Anomaly Detection

no code implementations6 May 2018 Shubhranshu Shekhar, Leman Akoglu

We introduce a new unsupervised anomaly detection ensemble called SPI which can harness privileged information - data available only for training examples but not for (future) test examples.

Unsupervised Anomaly Detection

Explaining Anomalies in Groups with Characterizing Subspace Rules

1 code implementation20 Aug 2017 Meghanath Macha, Leman Akoglu

We consider a complementary problem that has a much sparser literature: anomaly description.

Anomaly Detection Descriptive

Sequential Ensemble Learning for Outlier Detection: A Bias-Variance Perspective

no code implementations18 Sep 2016 Shebuti Rayana, Wen Zhong, Leman Akoglu

In this work, we design a new ensemble approach for outlier detection in multi-dimensional point data, which provides improved accuracy by reducing error through both bias and variance.

Binary Classification Clustering +3

BIRDNEST: Bayesian Inference for Ratings-Fraud Detection

no code implementations19 Nov 2015 Bryan Hooi, Neil Shah, Alex Beutel, Stephan Gunnemann, Leman Akoglu, Mohit Kumar, Disha Makhija, Christos Faloutsos

To combine these 2 approaches, we formulate our Bayesian Inference for Rating Data (BIRD) model, a flexible Bayesian model of user rating behavior.

Bayesian Inference Fraud Detection

Robust Semi-Supervised Classification for Multi-Relational Graphs

no code implementations19 Oct 2015 Junting Ye, Leman Akoglu

We provide a careful analysis of the inferred weights, based on which we devise an algorithm that filters out irrelevant and noisy graphs and produces weights proportional to the informativeness of the remaining graphs.

Classification General Classification +1

Less is More: Building Selective Anomaly Ensembles

no code implementations8 Jan 2015 Shebuti Rayana, Leman Akoglu

In this work, we tap into this gap and propose a new ensemble approach for anomaly mining, with application to event detection in temporal graphs.

Clustering Event Detection

Graph-based Anomaly Detection and Description: A Survey

1 code implementation18 Apr 2014 Leman Akoglu, Hanghang Tong, Danai Koutra

This survey aims to provide a general, comprehensive, and structured overview of the state-of-the-art methods for anomaly detection in data represented as graphs.

Social and Information Networks Cryptography and Security

Want a Good Answer? Ask a Good Question First!

no code implementations27 Nov 2013 Yuan Yao, Hanghang Tong, Tao Xie, Leman Akoglu, Feng Xu, Jian Lu

Community Question Answering (CQA) websites have become valuable repositories which host a massive volume of human knowledge.

Community Question Answering

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