As an emerging distributed learning paradigm, Federated Learning (FL) facilitates collaborative training among multiple clients without sharing raw data. However, the classic FL still faces significant challenges due to feature/model heterogeneity and catastrophic forgetting, which seriously hinder knowledge transfer and cause the forgetting of previous knowledge. To address these important challenges, we propose FBCL, a novel generalizable heterogeneity-aware Federated features and Basic-matrix Consistency Learning to balance intra-domain discriminability and inter-domain generalization. For feature/model heterogeneity, we align the similarity of feature distribution and construct the high-dimensional basic matrix with irrelevant unlabeled data, thereby overcoming communication barriers and learning generalizable representations while maintaining strict privacy preservation. For catastrophic forgetting during local updating, we introduce constraints in high-dimensional features to retain inter-domain knowledge and then extract accurate knowledge by distilling old models to preserve worthy historical information. Using real-world unlabeled public datasets, extensive experiments validate the superiority of the proposed FBCL, which outperforms the state-of-the-art methods on different scenarios of image classification.

The emerging Federated Graph Learning (FGL) offers promising collaborative training on distributed graph data. However, malicious actors may contaminate data streams by falsifying node relationships on clients or conduct adversarial attacks on edge servers, causing degraded inference and privacy leakage. Although some studies focus on privacy-protection FGL, they do not consider robustness and membership privacy amidst data pollution and adversarial attacks. Moreover, classic FGL commonly adopts FedAvg but neglects the impact of uneven information flow from distinct subtopologies. To address these important challenges, we propose GuardFGL, a novel similarity-driven FGL that extracts minimal-sufficient information from polluted data to maintain strong adversarial robustness and protect membership privacy. First, we incorporate structural-aware and feature-selection learning to explore target-relevant edges and features, avoiding privacy leakage from raw data. Next, we design an original Federated Graph Information Bottleneck (FGIB) principle to supervise extracting well-compressed information, mitigating the interference of polluted data streams. Finally, we develop a similarity-driven federated aggregation with auxiliary local information to alleviate the impact of uneven information flow. Using the real-world testbed and benchmark graph datasets, extensive experiments demonstrate that GuardFGL can achieve superior robust prediction and better protect membership privacy than state-of-the-art methods under adversarial attacks.

By integrating subgraph learning with federated learning, federated subgraph learning realizes collaborative learning of subgraph information among distributed Unmanned Agents (UAs) while protecting data privacy, offering a promising solution for graph modeling in Internet of Unmanned Agents (IUA). However, due to the various manners of collecting data on different UAs, graph data exhibits the features of Non-Independent and Identically Distributed (Non-IID), while the structures and features of local graph data on UAs are quite diverse. These factors lead to convergence difficulties and insufficient generalization ability of federated subgraph learning during the training process. To address these important challenges, we propose PFedSL, a novel knowledge-sharing Personalized Federated Subgraph Learning framework for IUA. First, a new personalized model aggregation is performed based on the confidence score of UAs and their similarity to reduce the interference of Non-IID data on model performance. Next, a parameter selective activation is introduced for model updating to handle the heterogeneity issue of subgraph structural features. Finally, an original personalized single-view contrastive learning is designed to optimize node embedding, thereby enhancing local representation consistency. Using real-world benchmark graph datasets, extensive experiments demonstrate the superiority of the proposed PFedSL. The results show that PFedSL achieves higher node classification accuracy than state-of-the-art methods in different scenarios. Meanwhile, the effectiveness of the core components in PFedSL is validated via ablation studies.

Graph convolutional network (GCN) has gained widespread attention in semisupervised classification tasks. Recent studies show that GCN-based methods have achieved decent performance in numerous fields. However, most of the existing methods generally adopted a fixed graph that cannot dynamically capture both local and global relationships. This is because the hidden and important relationships may not be directed exhibited in the fixed structure, causing the degraded performance of semisupervised classification tasks. Moreover, the missing and noisy data yielded by the fixed graph may result in wrong connections, thereby disturbing the representation learning process. To cope with these issues, this article proposes a learnable GCN-based framework, aiming to obtain the optimal graph structures by jointly integrating graph learning and feature propagation in a unified network. Besides, to capture the optimal graph representations, this article designs dual-GCN-based meta-channels to simultaneously explore local and global relations during the training process. To minimize the interference of the noisy data, a semisupervised graph information bottleneck (SGIB) is introduced to conduct the graph structural learning (GSL) for acquiring the minimal sufficient representations. Concretely, SGIB aims to maximize the mutual information of both the same and different meta-channels by designing the constraints between them, thereby improving the node classification performance in the downstream tasks. Extensive experimental results on real-world datasets demonstrate the robustness of the proposed model, which outperforms state-of-the-art methods with fixed-structure graphs.

Federated Graph Learning (FGL) has garnered widespread attention by enabling collaborative training on multiple clients for semi-supervised classification tasks. However, most existing FGL studies do not well consider the missing inter-client topology information in real-world scenarios, causing insufficient feature aggregation of multi-hop neighbor clients during model training. Moreover, the classic FGL commonly adopts the FedAvg but neglects the high training costs when the number of clients expands, resulting in the overload of a single edge server. To address these important challenges, we propose a novel FGL framework, named SpreadFGL, to promote the information flow in edge-client collaboration and extract more generalized potential relationships between clients. In SpreadFGL, an adaptive graph imputation generator incorporated with a versatile assessor is first designed to exploit the potential links between subgraphs, without sharing raw data. Next, a new negative sampling mechanism is developed to make SpreadFGL concentrate on more refined information in downstream tasks. To facilitate load balancing at the edge layer, SpreadFGL follows a distributed training manner that enables fast model convergence. Using real-world testbed and benchmark graph datasets, extensive experiments demonstrate the effectiveness of the proposed SpreadFGL. The results show that SpreadFGL achieves higher accuracy and faster convergence against state-of-the-art algorithms.

The emerging Graph Convolutional Networks (GCNs) have attracted widespread attention in graph learning, due to their good ability of aggregating the information between higher-order neighbors. However, real-world graph data contains high noise and redundancy, making it hard for GCNs to accurately depict the complete relationships between nodes, which seriously degrades the quality of graph representations. Moreover, existing studies commonly ignore the distribution difference between feature and semantic spaces in graphs, causing inferior model generalization. To address these challenges, we propose DIB-RGCN, a novel robust GCN framework, to explore the optimal graph representation with the guidance of the well-designed dual information bottleneck principle. First, we analyze the reasons for distribution differences and theoretically prove that minimal sufficient representations in specific spaces cannot promise optimal performance for downstream tasks. Next, we design new dual channels to regularize feature and semantic spaces, eliminating the sharing of task-irrelevant information between spaces. Different from existing denoising algorithms that adopt a random dropping manner, we innovatively replace potential noisy features and edges with local neighboring representations. This design lowers edge-specific coefficient assignment, alleviating the interference of original representations while retaining graph structures. Further, we maximize the sharing of task-relevant information between feature and semantic spaces to alleviate the difference between them. Using real-world datasets, extensive experiments demonstrate the robustness of the proposed DIB-RGCN, which outperforms state-of-the-art methods on classification tasks.

With flexible mobility and broad communication coverage, Unmanned Aerial Vehicles (UAVs) have become an important extension of Multi-access Edge Computing (MEC) systems, exhibiting great potential for improving the performance of Federated Graph Learning (FGL). However, due to the limited computing and storage resources of UAVs, they may not well handle the redundant data and complex models, causing the inference inefficiency of FGL in UAV-assisted MEC systems. To address this critical challenge, we propose a novel LightWeight FGL framework, named LW-FGL, to accelerate the inference speed of classification models in UAV-assisted MEC systems. Specifically, we first design an adaptive Information Bottleneck (IB) principle, which enables UAVs to obtain well-compressed worthy subgraphs by filtering out the information that is irrelevant to downstream classification tasks. Next, we develop improved tiny Graph Neural Networks (GNNs), which are used as the inference models on UAVs, thus reducing the computational complexity and redundancy. Using real-world graph datasets, extensive experiments are conducted to validate the effectiveness of the proposed LW-FGL. The results show that the LW-FGL achieves higher classification accuracy and faster inference speed than state-of-the-art methods.

In recent years, reconstructing features and learning node representations by graph autoencoders (GAE) have attracted much attention in deep graph node clustering. However, existing works often overemphasize structural information and overlook the impact of real-world prevalent noise on feature learning and clustering with graph data, which may be detrimental to robust training. To address these issues, the utilization of a masking strategy that specifically focuses on feature reconstruction may mitigate these limitations. In this article, we propose a graph node clustering generative method named deep masked graph node clustering (DMGNC), which leverages a masked autoencoder to effectively reconstruct node features, enabling the discovery of latent information crucial for accurate node clustering. Additionally, a clustering self-optimization module is designed to guide the iterative update of our end-to-end clustering framework. Further, we extend the masked graph autoencoder (MGA) and develop a contrastive method called deep masked graph node contrastive clustering (DMGNCC), which applies the MGA to graph node contrastive learning at both the node level and the class level in a united model. Extensive experimental results on real-world graph benchmark datasets demonstrate the effectiveness and superiority of the proposed method.

Multi-view learning is a promising research field that aims to enhance learning performance by integrating information from diverse data perspectives. Due to the increasing interest in graph neural networks, researchers have gradually incorporated various graph models into multi-view learning. Despite significant progress, current methods face challenges in extracting information from multiple graphs while simultaneously accommodating specific downstream tasks. Additionally, the lack of a subsequent refinement process for the learned graph leads to the incorporation of noise. To address the aforementioned issues, we propose a method named generative essential graph convolutional network for multi-view semi-supervised classification. Our approach integrates the extraction of multi-graph consistency and complementarity, graph refinement, and classification tasks within a comprehensive optimization framework. This is accomplished by extracting a consistent graph from the shared representation, taking into account the complementarity of the original topologies. The learned graph is then optimized through downstream-specific tasks. Finally, we employ a graph convolutional network with a learnable threshold shrinkage function to acquire the graph embedding. Experimental results on benchmark datasets demonstrate the effectiveness of our approach.