Few-shot Heterogeneous Graph Learning via Cross-domain Knowledge Transfer

Graph few-shot learning seeks to alleviate the label scarcity problem resulting from the difficulties and high cost of data annotations in graph learning. However, the overwhelming solutions in graph few-shot learning focus on homogeneous graphs, ignoring the ubiquitous heterogeneous graphs (HGs), which represent real-world complex systems and domain knowledge with multi-typed nodes interconnected by multi-typed edges. To this end, we study the cross-domain few-shot learning problem over HGs and develop a novel model for Cross-domain Heterogeneous Graph Meta learning (CrossHG-Meta). The general idea is to promote the HG node classification in the data-scarce target domain by transferring meta-knowledge from a series of HGs in data-rich source domains. The key challenges are to 1) combat the heterogeneity in HGs to acquire the transferable meta-knowledge; 2) handle the domain shifts between the source HG and target HG; and 3) fast adapt to novel target tasks with few-shot annotated examples. Regarding the graph heterogeneity, CrossHG-Meta firstly builds a graph encoder to aggregate heterogeneous neighborhood information from multiple semantic contexts. Secondly, to tackle domain shifts, a cross-domain meta-learning strategy is proposed to include a domain critic, which is designed to explicitly lead cross-domain adaptation for meta-tasks in different domains and improve model generalizability. Last, to further alleviate data scarcity, CrossHG-Meta leverages unlabelled information in source domains with auxiliary self-supervised learning task to provide cross-domain contrastive regularization alongside the meta-optimization process to facilitate node embedding. Extensive experimental results on three multi-domain HG datasets demonstrate that the proposed model outperforms various state-of-the-art baselines for multiple few-shot node classification tasks under the cross-domain setting.