Towards Data Privacy and Utility in the Applications of Graph Neural Networks

Graph Neural Networks (GNNs) are essential for handling graph-structured data, often containing sensitive information. It’s vital to maintain a balance between data privacy and usability. To address this, this dissertation introduces three studies aimed at enhancing privacy and utility in GNN applications, particularly in node classification, link prediction, and graph classification. The first work tackles celebrity privacy in social networks. We develop a novel framework using adversarial learning for link-privacy preserved graph embedding, which effectively safeguards sensitive links without compromising the graph’s structure and node attributes. This approach is validated using real social network data. In the second work, we confront challenges in federated graph learning with non-independent and identically distributed (non-IID) data. We introduce PPFL-GNN, a privacy-preserving federated graph neural network framework that mitigates overfitting on the client side and inefficient aggregation on the server side. It leverages local graph data for embeddings and employs embedding alignment techniques for enhanced privacy, addressing the hurdles in federated learning on non-IID graph data. The third work explores Few-Shot graph classification, which aims to classify novel graph types with limited labeled data. We propose a unique framework combining Meta-learning and contrastive learning to better utilize graph structures in molecular and social network datasets. Additionally, we offer benchmark graph datasets with extensive node-attribute dimensions for future research. These studies collectively advance the field of graph-based machine learning by addressing critical issues of data privacy and utility in GNN applications

Learning models for semantic classification of insufficient plantar pressure images

Establishing a reliable and stable model to predict a target by using insufficient labeled samples is feasible and effective, particularly, for a sensor-generated data-set. This paper has been inspired with insufficient data-set learning algorithms, such as metric-based, prototype networks and meta-learning, and therefore we propose an insufficient data-set transfer model learning method. Firstly, two basic models for transfer learning are introduced. A classification system and calculation criteria are then subsequently introduced. Secondly, a dataset of plantar pressure for comfort shoe design is acquired and preprocessed through foot scan system; and by using a pre-trained convolution neural network employing AlexNet and convolution neural network (CNN)- based transfer modeling, the classification accuracy of the plantar pressure images is over 93.5%. Finally, the proposed method has been compared to the current classifiers VGG, ResNet, AlexNet and pre-trained CNN. Also, our work is compared with known-scaling and shifting (SS) and unknown-plain slot (PS) partition methods on the public test databases: SUN, CUB, AWA1, AWA2, and aPY with indices of precision (tr, ts, H) and time (training and evaluation). The proposed method for the plantar pressure classification task shows high performance in most indices when comparing with other methods. The transfer learning-based method can be applied to other insufficient data-sets of sensor imaging fields