Abstracts:Event reasoning is to reason with events and certain inter-event relations. These cutting-edge techniques possess crucial and fundamental capabilities that underlie various applications. Large language models (LLMs) have made advances in event reasoning owing to their wealth of training. However, the LLMs commonly used today still do not consistently demonstrate proficiency in managing event reasoning as humans. This discrepancy arises from not explicitly modeling events and their relations and insufficient knowledge of event relations. In addition, the different reasoning paradigms of the LLMs are trained in an imbalanced way. In this paper, we propose $\textsc {WizardEvent}$WizardEvent, to synthesize data from the unlabeled corpus with the proposed hybrid event-aware instruction tuning. Specifically, we first represent the events and their relation in a novel structure and then extract the knowledge from the raw text. Second, we introduce hybrid event reasoning paradigms with four reasoning formats. Lastly, we wrap our constructed event relational knowledge with the paradigms to create the instruction tuning dataset. We fine-tune the model with this enriched dataset, significantly improving the event reasoning. The performance of $\textsc {WizardEvent}$WizardEvent is rigorously evaluated through extensive experiments. The results demonstrate that $\textsc {WizardEvent}$WizardEvent substantially outperforms baselines, indicating the effectiveness of our approach.

Abstracts:Spatial crowdsourcing (SC) is becoming increasingly popular recently. As a critical issue in SC, task assignment currently faces challenges due to the imbalanced spatiotemporal distribution of tasks. Hence, many related studies and applications focusing on cross-platform task allocation in SC have emerged. Existing work primarily focuses on the maximization of total revenue for inner platform in cross task assignment. In this work, we formulate a SC problem called Cross Dynamic Task Assignment (CDTA) to maximize the overall utility and propose improved solutions aiming at creating a win-win situation for inner platform, task requesters, and outer workers. We first design a hybrid batch processing framework and a novel cross-platform incentive mechanism. Then, with the purpose of allocating tasks to both inner and outer workers, we present a KM-based algorithm that gets the accurate assignment result in each batch and a density-aware greedy algorithm with high efficiency. To maximize the revenue of inner platform and outer workers simultaneously, we model the competition among outer workers as a potential game that is shown to have at least one pure Nash equilibrium and develop a game-theoretic method. Additionally, a simulated annealing-based improved algorithm is proposed to avoid falling into local optima. Last but not least, since random thresholds lead to unstable results when picking tasks that are preferentially assigned to inner workers, we devise an adaptive threshold selection algorithm based on multi-armed bandit to further improve the overall utility. Extensive experiments demonstrate the effectiveness and efficiency of our proposed algorithms on both real and synthetic datasets.

Abstracts:While stock prediction task traditionally relies on volume-price and fundamental data to predict the return ratio or price movement trend, sentiment factors derived from social media platforms such as StockTwits offer a complementary and useful source of real-time market information. However, we find that most social media posts, along with the public sentiment they reflect, provide limited value for trading predictions due to their noisy nature. To tackle this, we propose a novel dynamic expert tracing algorithm that filters out non-informative posts and identifies both true and inverse experts whose consistent predictions can serve as valuable trading signals. Our approach achieves significant improvements over existing expert identification methods in stock trend prediction. However, when using binary expert predictions to predict the return ratio, similar to all other expert identification methods, our approach faces a common challenge of signal sparsity with expert signals cover only about 4% of all stock-day combinations in our dataset. To address this challenge, we propose a dual graph attention neural network that effectively propagates expert signals across related stocks, enabling accurate prediction of return ratios and significantly increasing signal coverage. Empirical results show that our propagated expert-based signals not only exhibit strong predictive power independently but also work synergistically with traditional financial features. These combined signals significantly outperform representative baseline models in all quant-related metrics including predictive accuracy, return metrics, and correlation metrics, resulting in more robust investment strategies. We hope this work inspires further research into leveraging social media data for enhancing quantitative investment strategies.

Abstracts:Graph retrieval (GR), a ranking procedure that aims to sort the graphs in a database by their relevance to a query graph in decreasing order, has wide applications across diverse domains, such as visual object detection and drug discovery. Existing Graph Retrieval (GR) approaches usually compare graph pairs at a detailed level and generate quadratic similarity scores. In realistic scenarios, conducting quadratic fine-grained comparisons is costly. However, coarse-grained comparisons would result in performance loss. Moreover, label scarcity in real-world data brings extra challenges. To tackle these issues, we investigate a more realistic GR problem, namely, efficient graph retrieval (EGR). Our key intuition is that, since there are numerous underutilized unlabeled pairs in realistic scenarios, by leveraging the additional information they provide, we can achieve speed-up while simplifying the model without sacrificing performance. Following our intuition, we propose an efficient model called Dual-Tower Model with Dividing, Contrasting and Alignment (TowerDNA). TowerDNA utilizes a GNN-based dual-tower model as a backbone to quickly compare graph pairs in a coarse-grained manner. In addition, to effectively utilize unlabeled pairs, TowerDNA first identifies confident pairs from unlabeled pairs to expand labeled datasets. It then learns from remaining unconfident pairs via graph contrastive learning with geometric correspondence. To integrate all semantics with reduced biases, TowerDNA generates prototypes using labeled pairs, which are aligned within both confident and unconfident pairs. Extensive experiments on diverse realistic datasets demonstrate that TowerDNA achieves comparable performance to fine-grained methods while providing a 10× speed-up.

Abstracts:Spatio-temporal traffic data imputation is a fundamental component in intelligent transportation systems, which can significantly improve data quality and enhance the accuracy of downstream data mining tasks. Recently, low-rank tensor representation has shown great potential for spatio-temporal traffic data imputation. However, the low-rank assumption focuses on the global structure, neglecting the critical spatial topology and local temporal dependencies inherent in spatio-temporal data. To address these issues, we propose a topology-induced low-rank tensor representation (TILR), which can accurately capture the underlying low-rankness of the spatial multi-scale features induced by topology knowledge. Moreover, to exploit local temporal dependencies, we suggest a learnable convolutional regularization framework, which not only includes some classical convolution-based regularizers but also leads to the discovery of new convolutional regularizers. Equipped with the suggested TILR and convolutional regularizer, we build a unified low-rank tensor model harmonizing spatial topology and temporal dependencies for traffic data imputation, which is expected to deliver promising performance even under extreme and complex missing scenarios. To solve the proposed nonconvex model, we develop an efficient alternating direction method of multipliers (ADMM)-based algorithm and analyze its computational complexity. Extensive experiments demonstrate that the proposed model outperforms state-of-the-art baselines for various missing scenarios. These results reveal the critical synergy between topology-aware low-rank constraint and temporal dynamic modeling for spatio-temporal data imputation.

Abstracts:With growing demands for data privacy and model robustness, graph unlearning (GU), which erases the influence of specific data on trained GNN models, has gained significant attention. However, existing exact unlearning methods suffer from either low efficiency or poor model performance. While more utility-preserving and efficient, current approximate methods require access to the forget set during unlearning, which makes them inapplicable in immediate deletion scenarios, thereby undermining privacy. Additionally, these approximate methods, which attempt to directly perturb model parameters, still raise significant concerns regarding unlearning power in empirical studies. To fill the gap, we propose Transferable Condensation Graph Unlearning (TCGU), a data-centric solution to graph unlearning. Specifically, we first develop a two-level alignment strategy to pre-condense the original graph into a compact yet utility-preserving dataset for subsequent unlearning tasks. Upon receiving an unlearning request, we fine-tune the pre-condensed data with a low-rank plugin, to directly align its distribution with the remaining graph, thus efficiently revoking the information of deleted data without accessing them. A novel similarity distribution matching approach and a discrimination regularizer are proposed to effectively transfer condensed data and preserve its utility in GNN training, respectively. Finally, we retrain the GNN on the transferred condensed data. Extensive experiments on 7 benchmark datasets demonstrate that TCGU can achieve superior performance in terms of model utility, unlearning efficiency, and unlearning efficacy compared to existing GU methods. To the best of our knowledge, this is the first study to explore graph unlearning with immediate data removal using a data-centric approximate method.

Abstracts:Multi-hop Knowledge Graph Reasoning (KGR) seeks to identify accurate answers within Knowledge Graphs (KGs) via multi-step reasoning, predominantly utilizing reinforcement learning (RL) to enhance the efficiency of the reasoning process. Unlike traditional Knowledge Graph Embedding (KGE) methods, RL-based approaches offer superior interpretability. However, these methods often underperform due to two critical limitations: (1) their over-reliance on Horn rules for reasoning paths, which restricts their expressive power; and (2) inadequate utilization of reasoning states during the process. To address these issues, we propose a novel RL-based framework, RAR, which shifts focus from individual paths to subgraph structures for more robust predictions. RAR frames the retrieval of reasoning subgraphs from the KG as a Markov Decision Process (MDP) and incorporates a subgraph retriever. To efficiently explore the extensive subgraph space, we integrate multi-agent RL to enhance the retriever’s capabilities. Additionally, RAR features an advanced analyst module that meticulously examines reasoning states. These modules function iteratively: the retriever expands the subgraph, followed by the analyst module’s in-depth analysis. The insights gained are then used to inform subsequent retrieval steps. Ultimately, the predicted scores from both modules are synthesized to produce more precise posterior scores. Experimental results across multiple datasets demonstrate RAR’s efficacy, showcasing a notable improvement over existing state-of-the-art RL-based KGR methods.

Abstracts:The COVID-19 pandemic not only triggered a global health crisis but also amplified public panic through the rapid spread of misinformation. Understanding public sentiment and identifying the causes of sudden sentiment spikes is therefore critical for ensuring accurate information dissemination and guiding effective policymaking. However, mining such causes from social media remains challenging. Tweets collected during sentiment spike periods are often short, noisy, and dominated by repetitive background topics, making it difficult for existing topic models to separate emerging issues from long-standing discussions. To address these challenges, we propose the Sentiment Variation-aware Emerging Topics Mining Model (SVETM), a probabilistic graphical framework that leverages user sentiment variation between adjacent time windows as a guiding signal to distinguish emerging topics from background content. We further reformulate inference as a maximum a posteriori (MAP) problem and develop an efficient variational inference algorithm for scalable learning. Extensive experiments on a large-scale COVID-19 Twitter dataset demonstrate that SVETM outperforms strong baselines in terms of topic coherence, interpretability, and its ability to uncover the underlying causes of sentiment spikes.

Abstracts:Graph Neural Networks (GNNs) have become widely popular across various applications, with their vulnerability to adversarial attacks being a key concern. Among the different types of graph attacks, Restricted Black-box Attacks (RBAs) present the most strict constraints, as attackers have limited access only to node features and graph structure. Existing RBAs rely on homophily assumptions or shift-based losses as their objectives to conduct structural perturbations, but we demonstrate that all the approaches fail on heterophilic graphs. To address this challenge, we introduce node-wise distance metrics as the objective to fundamentally quantify the quality of the graph structure after perturbations. Our theoretical results show that the proposed objective allows RBAs to effectively handle graphs beyond homophily. Leveraging this objective, we propose HetAttack, a scalable method that significantly reduces the distinguishability of nodes on the victim graph. Experiments on both synthetic and real-world graphs confirm the efficacy of HetAttack across varying levels of homophily, achieving performance comparable to split-unknown white-box attacks without prior knowledge of labels or the target model.

Abstracts:A recent trend in urban computing involves utilizing multi-modal data for urban region embedding, which can be further expanded in a variety of downstream urban sensing tasks. Many previous studies rely on multi-graph embedding techniques and follow a two-stage paradigm: first building a $k$k-nearest neighbor graph based on fixed region correlations for each view, and then blending multi-view information in a posterior stage to learn region representations. However, multi-graph construction and multi-graph representation learning are not associated in most existing two-stage studies, and the relationship between them is not leveraged, which can provide complementary information to each other. In this paper, we unify these two stages into one by constructing learnable weighted complete graphs of regions and propose a new one-stage Region Embedding method with Adaptive region correlation Discovery (READ). Specifically, READ comprises three modules, including a disentangled region feature learning module utilizing a city-context Transformer to encode regions’ semantic and mobility features, and an adaptive weighted multi-graph construction module that builds multiple complete graphs with learnable weights based on disentangled features of regions. In addition, we propose a multi-graph representation learning module to yield effective region representations that integrate information from multiple graphs. We conduct thorough experiments on three downstream tasks to assess READ. Experimental results demonstrate that READ considerably outperforms state-of-the-art baseline methods in urban region embedding.