Cross-Domain Recommendation via Progressive Structural Alignment

Cross-domain recommendation, as a cutting-edge technology to settle data sparsity and cold start problems, is gaining increasingly popular. Existing research paradigms primarily focus on leveraging the representation of overlapping entities, such as representation aggregation or cross-domain consistency constraints, to facilitate knowledge transfer and enhance the performance of single-domain or dual-domain recommender systems. Even though these approaches bring significant promotions, they still suffer from optimization bottlenecks when faced with sparse overlapping users, which often occurs in reality. Unlocking the full potential of overlapping user information and exploring novel sources of cross-domain knowledge are pivotal in addressing this challenge effectively. On account of this, this paper proposes an innovative cross-domain recommendation framework, namely SEAGULL , to promote dual-target recommendation performance in line with these two perspectives. We bolster the utilization of overlapping user knowledge and extract non-overlapping user interests by refining the message passing mechanism in a unified heterogeneous cross-domain graph and facilitating the transfer of latent structural relationships among users. Specifically, we first construct the interaction of two domains as a unified cross-domain heterogeneous graph and design a novel attention mechanism to incorporate cross-domain collaboration signals between users and items. Second, we perform user structure alignment from global and local levels to extend semantic transfer and information augmentation. Finally, unlike previous work that directly incorporates mixed cross-domain knowledge, we employ a gentle and progressive cross-domain transfer strategy to reduce empirical risk loss. Extensive experiments on five tasks derived from three data sets fully demonstrate the effectiveness of SEAGULL .