Federated recommendation enables collaborative model training while keeping user interaction data on local clients. A central problem in federated recommendation is how to aggregate useful information across clients for personalized recommendation. Existing personalized aggregation methods usually construct client relations from predefined parameter-based assumptions, such as parameter similarity or complementarity, and use these relations to determine aggregation weights. However, such methods construct a single global relation, which is insufficient to capture the hierarchical and multi-granularity nature of user relations in recommendation. Moreover, these predefined relations cannot directly reflect whether the related clients can improve prediction performance after aggregation. To address these limitations, we propose FedHUR, a federated recommendation framework for learning hierarchical utility-guided client relations. FedHUR takes item-item filters as the object for relation construction and aggregation. Specifically, it first aggregates and clusters each client's local information to obtain global hierarchical information. Each client computes hierarchical utility signals based on its local information and the global hierarchical information, indicating which collaborative information is useful for improving its prediction. The server uses these utility signals to retrieve clients that are useful to that client for further personalized aggregation. Extensive experiments on five real-world datasets show that FedHUR consistently outperforms existing federated recommendation baselines, demonstrating the effectiveness of hierarchical utility-guided client relation learning. Code is available at https://github.com/Mingzhe-Han/FedHUR.
Ming-Zhe Han, Jia-Hao Liu, Dong-Sheng Li et al.· 0 citations
Cross-domain sequential recommendation (CDSR) improves target-domain prediction by leveraging multi-domain interaction histories. Most CDSR methods rely on shared entities or co-occurrence signals, which become unreliable when overlap is limited, and atomic ID representations further generalize poorly to long-tail or unseen items as cross-domain distribution shifts exacerbate this problem. Recent generative CDSR methods enable cross-domain transfer without relying on raw ID alignment by generating content-grounded semantic IDs (SIDs) for cross-domain alignment. However, two challenges remain, including (i) user-item asymmetry, with items discretized for generation whereas user preferences are encoded only implicitly in sequence representations, limiting semantic-level preference control; and (ii) selective transfer, making it difficult to assess source-domain signals against the target preference representation without an explicit discrete user anchor aligned with item IDs, which can lead to unintended transfer of irrelevant signals. This work presents UniGCRec, which constructs a cross-domain user profile from multi-domain histories and quantizes both users and items into CSC-IDs that integrate semantic and collaborative signals. This symmetric quantization places user and item representations in the same discrete CSC-ID space, effectively mitigating user-item asymmetry and enabling preference-aware selective transfer under low-overlap settings. The generator is conditioned on a user CSC-ID prefix and the target domain item CSC-ID history for next-item generation, with trie-constrained decoding ensuring target domain validity. Experiments on public multi-domain benchmarks show consistent gains over strong baselines, with particularly strong gains on several target domains.
Chaoyue Ding, Jiahao Liu, Dongsheng Li et al.· Proceedings of the 32nd ACM...· 0 citations
Cross-domain sequential recommendation (CDSR) improves target-domain prediction by leveraging multi-domain interaction histories. Most CDSR methods rely on shared entities or co-occurrence signals, which become unreliable when overlap is limited, and atomic ID representations further generalize poorly to long-tail or unseen items as cross-domain distribution shifts exacerbate this problem. Recent generative CDSR methods enable cross-domain transfer without relying on raw ID alignment by generating content-grounded semantic IDs (SIDs) for cross-domain alignment. However, two challenges remain, including (i) user-item asymmetry, with items discretized for generation whereas user preferences are encoded only implicitly in sequence representations, limiting semantic-level preference control; and (ii) selective transfer, making it difficult to assess source-domain signals against the target preference representation without an explicit discrete user anchor aligned with item IDs, which can lead to unintended transfer of irrelevant signals. This work presents UniGCRec, which constructs a cross-domain user profile from multi-domain histories and quantizes both users and items into CSC-IDs that integrate semantic and collaborative signals. This symmetric quantization places user and item representations in the same discrete CSC-ID space, effectively mitigating user-item asymmetry and enabling preference-aware selective transfer under low-overlap settings. The generator is conditioned on a user CSC-ID prefix and the target domain item CSC-ID history for next-item generation, with trie-constrained decoding ensuring target domain validity. Experiments on public multi-domain benchmarks show consistent gains over strong baselines, with particularly strong gains on several target domains.
Chaoyue Ding, Jiahao Liu, Dongsheng Li et al.· Proceedings of the 32nd ACM...· 0 citations
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