Dynamic graph neural networks (DyGNNs) currently struggle with handling distribution shifts that naturally arise when training and test data follow similar but non-identical distributions. As the generation of dynamic graphs is strongly influenced by latent environments, it is critical to investigate their impacts on the generalization behavior of DyGNNs. We therefore establish a connection between the temporal message-passing scheme employed by DyGNNs and their generalization performance under distribution shifts. Our analysis reveals that environment-specific factors misguide the learning process and lead to unsatisfactory out-of-distribution (OOD) generalization. Based on this insight, we propose MoVE, a Mixture of Variational Experts network to mitigate complex distribution shifts in dynamic graphs. MoVE adopts a hierarchical variational architecture that extrapolates latent representations into a mixture of distribution shifts as pseudo-environments. Additionally, we incorporate a Mixture-of-Experts (MoE) framework with a novel training objective that aligns the outputs of different experts to produce invariant representations. Extensive experiments on various dynamic graphs, including both real-world and synthetic datasets, demonstrate that our model significantly outperforms state-of-the-art techniques.

Graph Neural Networks (GNNs) have demonstrated remarkable success in various scenarios. However, their impressive performance is under the assumption of class balance (i.e., equal training sample distribution across various categories). Once trapped in the class-imbalanced issue, the GNN-based models typically under-represent the minority ones, resulting in decreased performance compared to balanced graphs. A promising solution is to balance the graph in a generative manner. However, the existing studies overlook the consistency between the synthesized sample and its corresponding class. Furthermore, the homophily assumption (i.e., like attracts like) undermines the topological diversity of graphs, thereby complicating the capability of models to capture the true distribution and boundaries of the categories. To this end, we propose aConsistency-Aware andLooseHomophily guided generative method for class-imbalanced graphs, namelyGraphCALH. Specifically, we design a consistency-aware feature synthesis method to balance the node- wise characteristics and the class- wise commonality for the synthesized samples. Moreover, we devise a loose homophily guided topology modeling method to enrich the topological diversity and simplify category boundaries. The experimental results on eleven class-imbalanced datasets demonstrate that the proposed GraphCALH outperforms ten state-of-the-art methods. The source code of this work will be uploaded to Github.

In recent years, the study of real-world graphs has revealed their inherent heterogeneity, prompting growing research interest in heterogeneous graphs. Characterized by diverse node and relation types, heterogeneous graphs have led to the development of heterogeneous graph neural networks , which possess the remarkable ability of modeling such heterogeneity. Consequently, researchers have embraced these networks, applying them in various domains. A prevalent approach is using meta-path based methods in heterogeneous graph neural networks . However, a significant limitation arises from the fact that such methods tend to overlook vital attribute information within intermediate nodes and disregard relevant semantics across various meta-paths. To address the above limitations, we propose a new model named HGNN-MRCS. Specifically, HGNN-MRCS incorporates three key components, i.e., a relation aware module to encapsulate the attribute information of the intermediate nodes; a meta-path aware technique to facilitate learning of semantic information of each meta-path and enable higher-order representation learning ; and a knowledge distillation strategy to learn relevant semantics across meta-paths and fuse them. Experimental results on four real-world datasets demonstrate the superior performance of this work over the SOAT methods. The source codes of this work are available at https://github.com/ZZY-GraphMiningLab/HGNN-MRCS .

Graphs are widely used to model various practical applications. In recent years, graph convolution networks (GCNs) have attracted increasing attention due to the extension of convolution operation from traditional grid data to graph one. However, the representation ability of current GCNs is undoubtedly limited because existing work fails to consider feature interactions. Toward this end, we propose a Dual Feature Interaction-based GCN. Specifically, it models feature interaction in the aspects of 1) node features where we use Newton's identity to extract different-order cross features implicit in the original features and design an attention mechanism to fuse them; and 2) graph convolution where we capture the pairwise interactions among nodes in the neighborhood to expand a weighted sum operation. We evaluate the proposed model with graph data from different fields, and the experimental results on semi-supervised node classification and link prediction demonstrate the effectiveness of the proposed GCN. The data and source codes of this work are available athttps://github.com/ZZY-GraphMiningLab/DFI-GCN.

Traditional process discovery techniques mine process models based upon event traces giving little consideration to workflow relevant data recorded in event logs. The neglect of such information usually leads to incorrect discovered models, especially when activities have decomposable cyclic dependencies. To address this problem, the recorded workflow relevant data and decision tree learning technique are utilized to classify cases into case clusters. Each case cluster contains causality and concurrency activity dependencies only. Then, a set of activity ordering relations are derived based on case clusters. And a synchronization-core-based process model is discovered from the ordering relations and composite cases. Finally, the discovered model is transformed to a BPMN model. The proposed approach is validated with a medical treatment process and an open event log. Meanwhile, a prototype system is presented.