The widespread use of social-media graphs has provided a convenient channel for rumor propagation. Rapid localization of rumor sources is therefore crucial for mitigating diffusion and enabling punitive countermeasures. Source Localization (SL) aims to identify the origin nodes given partial infection observations. Although deep-learning-based SL approaches outperform traditional estimators, three fundamental limitations remain: (i) Model Complexity —existing methods enrich node embeddings with cascades of auxiliary features, yielding high-capacity but excessively complex representations, leading to an exponential increase in the number of model parameters; (ii) Annotation gap —to overcome the scarcity of real-world misinformation cascades, current pipelines repeatedly simulate diffusion from a fixed seed, eroding robustness on true, few-shot outbreaks; and (iii) Computational bottleneck —full-model retraining or recurrent cascade simulation is required for every new task, which disqualifies the solutions from real-time deployment. Inspired by the success of prompt learning in NLP and graph learning, we propose LAPS, a Lightweight privilege-Allocation Prompting framework for Source localization. LAPS first trims parameter explosion and data scarcity by pre-training a graph-level source region classifier on adaptive subgraphs with source-prior diffusion data. It then enables few-shot SL via a privilege-allocation prompt module that updates <1% of all the parameters, avoiding model retraining to facilitate efficiency. Extensive experiments on five real-world networks demonstrate the effectiveness and efficiency of our prompt-based framework on few-shot source localization task.

Dynamic graph representation learning has emerged as a pivotal paradigm for modeling time-varying relational patterns in complex systems ranging from social networks to urban mobility. While existing methods achieve notable progress in temporal modeling, one critical challenge remains insufficiently addressed: identifying dual temporal evolution, i,e., instantaneous states and evolutionary trajectories. To address the challenge, we propose HMGNN, a novel dynamic graph learning framework that harmoniously integrates temporal dynamics modeling with stable structural representation learning, allowing adaptive pattern discovery while preserving feature consistency in evolving environments. Firstly, we propose a dynamic model that integrates a historical information perception module and a temporal aggregation module. The module converts the historical information into the model and adaptively measures the impact of the instantaneous and historical information effectively through the aggregation function. Secondly, we devise a dual-component model learning framework comprising contrastive learning and multi-granular temporal curriculum learning to holistically capture evolutionary dynamics. The contrastive learning component employs continuous-view contrastive alignment to preserve stable node feature across temporal evolution. Complementarily, our multi-granular temporal curriculum learning introduces masking mechanism to explicitly learn different time interval evolution patterns. Extensive experiments demonstrate the significant superiority of HMGNN against state-of-the-art dynamic graph learning methods in terms of all evaluation metrics.

Dynamic recommendation, focusing on modeling user preference from historical interactions and providing recommendations on current time, plays a key role in many personalized services. Recent works show that pre-trained dynamic graph neural networks (GNNs) can achieve excellent performance. However, existing methods by fine-tuning node representations at large scales demand significant computational resources. Additionally, the long-tail distribution of degrees leads to insufficient representations for nodes with sparse interactions, posing challenges for efficient fine-tuning. To address these issues, we introduce GraphSASA, a novel method for efficient fine-tuning in dynamic recommendation systems. GraphSASA employs test-time augmentation by leveraging the similarity of node representation distributions during hierarchical graph aggregation, which enhances node representations. Then it applies singular value decomposition, freezing the original vector matrix while focusing fine-tuning on the derived singular value matrices, which reduces the parameter burden of fine-tuning and improves the fine-tuning adaptability. Experimental results demonstrate that our method achieves state-of-the-art performance on three large-scale datasets.