Generalizable Graph Prompt Learning Framework with Model-level Prompt Injection and Two-Stage Prompt Tuning

Graph prompt learning represents a novel paradigm aimed at enhancing the performance of graph learning models on a variety of downstream tasks by providing specific graph prompts. Despite its promise, current graph prompt learning methods are limited by the following limitations. On the one hand, existing methods often rely on manually selected graph information or simple learnable vectors, which can introduce human biases and lack expressiveness. These methods also fall short in guiding models to induce historical prior knowledge and improve generalization. Furthermore, the direct end-to-end tuning strategy of prompts lacks a necessary gentle transition, which impacts model stability and generalization. To overcome these limitations, we introduce the generalizable graph prompt learning framework (GGPL), which incorporates model-level prompt injection and a two-stage prompt tuning strategy. GGPL focuses on encoding subgraph structures and attributes during pre-training and uses SimGRACE to predict subgraph similarities, enhancing the base model's generalization. The model-level prompt injection module, with its prompt embedding backbone and self-prompt generation, seamlessly integrates invariant knowledge. Our two-stage tuning strategy, including transition and task-specific tuning, ensures better guidance and stability. By designing learnable prompt tokens and fine-tuning them with task-specific information, GGPL enables the model to generalize more robustly to downstream tasks. We conduct extensive experiments on six benchmark datasets to verify the model's effectiveness.