Click-through Rate (CTR) prediction is crucial for online personalization platforms. Recent advancements have shown that modeling rich user behaviors can significantly improve the performance of CTR prediction. Current long-term user behavior modeling algorithms predominantly follow two cascading stages. The first stage retrieves subsequence related to the target item from the long-term behavior sequence, while the second stage models the relationship between the subsequence and the target item. Despite significant progress, these methods have two critical flaws. First, the retrieval query typically includes only target item information, limiting the ability to capture the user's diverse interests. Second, relational information, such as sequential and interactive information within the subsequence, is frequently overlooked. Therefore, it requires to be further mined to more accurately model user interests.

In recommendation systems, the traditional multi-stage paradigm, which includes retrieval and ranking, often suffers from information loss between stages and diminishes performance. Recent advances in generative models, inspired by natural language processing, suggest the potential for unifying these stages to mitigate such loss. This paper presents the Unified Generative Recommendation Framework (UniGRF), a novel approach that integrates retrieval and ranking into a single generative model. By treating both stages as sequence generation tasks, UniGRF enables sufficient information sharing without additional computational costs, while remaining model-agnostic. To enhance inter-stage collaboration, UniGRF introduces a ranking-driven enhancer module that leverages the precision of the ranking stage to refine retrieval processes, creating an enhancement loop. Besides, a gradient-guided adaptive weighter is incorporated to dynamically balance the optimization of retrieval and ranking, ensuring synchronized performance improvements. Extensive experiments demonstrate that UniGRF significantly outperforms existing models on benchmark datasets, confirming its effectiveness in facilitating information transfer. Ablation studies and further experiments reveal that UniGRF not only promotes efficient collaboration between stages but also achieves synchronized optimization. UniGRF provides an effective, scalable, and compatible framework for generative recommendation systems.

Recently, the dual-target cross-domain recommendation has been an emerging research problem, which aims to improve the performances of both source and target domains by transferring the preferences of overlapping users. Most of the existing work adopted a coarse-grained manner to detach general users’ preferences and associate them with domain-specific information for enhancing user representation learning, which fails to depict the differences in users’ diverse preferences and aggregate relevant preferences with improper propagation. To this end, in this article, we propose a multi-factor user representation pre-training framework, dubbed MF-GSLAE, with a focus on fine-grained preference learning and transferring. Specifically, we first propose a fine-grained factor representation pre-training paradigm. It projects the behavior records of both domains into several subspaces and introduces a compactness regularization to generate multiple fine-grained preference factors. Furthermore, we propose a multi-factor graph structure learning method within linear complexity to efficiently construct preference connections on different scales of users, which could aggregate the intrinsic relationship of user preferences in immediate embedding spaces to capture high-order information. Following the pre-training, we subsequently design a factor selection module with the bootstrapping mechanism to adaptively choose the corresponding domain-related preferences and transfer domain-shared information through partial overlapping factors for addressing the negative transfer problem. Finally, the optimization objectives of both domains are formalized in a multi-task learning framework and derive the learned user representation in an end-to-end training manner. Extensive experimental results on several publicly available datasets have not only demonstrated the effectiveness of the learned user representations with the comparison of state-of-the-art baselines but also indicated the interpretability and robustness. The code of our work is publicly available at https://github.com/USTC-StarTeam/MF-GSLAE .

Sequential recommendation (SR) aims to predict items that users may be interested in based on their historical behavior sequences. We revisit SR from a novel information-theoretic perspective and find that conventional sequential modeling methods fail to adequately capture the randomness and unpredictability of user behavior. Inspired by fuzzy information processing theory, this paper introduces the DDSR model, which uses fuzzy sets of interaction sequences to overcome the limitations and better capture the evolution of users' real interests. Formally based on diffusion transition processes in discrete state spaces, which is unlike common diffusion models such as DDPM that operate in continuous domains. It is better suited for discrete data, using structured transitions instead of arbitrary noise introduction to avoid information loss. Additionally, to address the inefficiency of matrix transformations due to the vast discrete space, we use semantic labels derived from quantization or RQ-VAE to replace item IDs, enhancing efficiency and improving cold start issues. Testing on three public benchmark datasets shows that DDSR outperforms existing state-of-the-art methods in various settings, demonstrating its potential and effectiveness in handling SR tasks.