Existing solutions for bundle recommendation (BR) have achieved remarkable effectiveness for predicting the user’s preference for prebuilt bundles. However, bundle-item (B-I) affiliation will vary dynamically in real scenarios. For ex ample, a bundle themed as ‘casual outfit’ may add ‘hat’ or remove ‘watch’ due to factors such as seasonal variations, changes in user preferences or inventory adjustments. Our empirical study demonstrates that the performance of main stream BR models may fluctuate or decline under item-level variability. This paper makes the first attempt to address the above problem and proposes Residual Diffusion for Bundle Recommendation (RDiffBR) as a model-agnostic generative framework which can assist a BR model in adapting this sce nario. During the initial training of the BR model, RDiffBR employs a residual diffusion model to process the item-level bundle embeddings which are generated by the BR model to represent bundle theme via a forward-reverse process. In the inference stage, RDiffBR reverses item-level bundle em beddings obtained by the well-trained bundle model under B-I variability scenarios to generate the effective item-level bundle embeddings. In particular, the residual connection in our residual approximator significantly enhances BR mod els’ ability to generate high-quality item-level bundle embed dings. Experiments on six BRmodelsandfourpublicdatasets from different domains show that RDiffBR improves the per formance of Recall and NDCG of backbone BR models by up to 23%, while only increases training time about 4%.

Bundle recommender system is divided into two main stages: bundle editing and bundle recommendation. While substantial research progress has been made in each stage, in practical application scenarios, bundle compositions and the final recommended bundles mutually influence each other: the continuously editing bundle compositions affect the recommendation results, while user feedback on recommended bundles in turn guides the refinement of bundle compositions. This paper presents the first comprehensive reproducibility study of the complete bundle recommendation pipeline. We implement eight bundle-level editing methods, nine item-level editing methods, and seven state-of-the-art bundle recommendation models, and evaluate their performance across six real-world datasets. Our empirical analysis reveals several key findings. First, bundle-level editing faces the challenge of generating high-quality bundles. Second, in the item-level editing, the replacement operation emerges as a universal bottleneck across all methods. Third, in the recommendation stage, recommendation models exhibit varying performance across different interaction density scenarios (e.g., cold-start). Finally, bundle recommendation suffers degraded performance when integrating item-level editing and bundle recommendation within a unified pipeline. Overall, there is the systemic limitation of bundle recommendation: prior work has focused on optimizing individual stages independently, disregarding the interdependencies throughout the entire recommendation system. These findings highlight the urgent need to develop end-to-end solutions that can holistically address the bundle editing and recommendation workflow. Our repository is now available for public access via https://github.com/anyr123/Bundle_Edit_Rec_SIGIR26.

Cold-start bundle recommendation focuses on modeling new bundles with insufficient information to provide recommendations. Advanced bundle recommendation models usually learn bundle representations from multiple views (e.g., user-bundle interaction views) at both bundle and item levels. Consequently, the cold-start problem for bundles is more challenging than that for traditional items due to the dual-level multi-view complexity. For cold-start bundle recommendation, we propose a novel Mixture of Diffusion Experts (MoDiffE) framework, which employs a divide-and-conquer strategy and consists of three parts: (1) Division : The bundle cold-start problem is divided into view-specific but unified sub-problems: the poor representation of feature-missing bundles in prior-embedding models. (2) Conquest : Diffusion models uniformly solve all sub-problems by directly generating diffusion representations without depending on specific features. (3) Combination : A cold-aware hierarchical Mixture of Experts (MoE) is employed to adaptively combine results of the sub-problems into final recommendations. Additionally, MoDiffE proposes a cold-start gating augmentation method to enable gating for cold bundles. In experiments on three real-world datasets, MoDiffE significantly outperforms existing solutions in cold-start bundle recommendation. It achieves up to a 0.1027 Recall@20 improvement in cold-start scenarios and up to a 47.43% relative improvement in all-bundle scenarios.

Meal recommendation, as a typical health-related recommendation task, contains complex relationships between users, courses, and meals. Among them, meal-course affiliation associates user-meal and user-course interactions. However, an extensive literature review demonstrates that there is a lack of publicly available meal recommendation datasets including meal-course affiliation. Meal recommendation research has been constrained in exploring the impact of cooperation between two levels of interaction on personalization and healthiness. To pave the way for meal recommendation research, we introduce a new benchmark dataset called MealRec^+. Due to constraints related to user health privacy and meal scenario characteristics, the collection of data that includes both meal-course affiliation and two levels of interactions is impeded. Therefore, a simulation method is adopted to derive meal-course affiliation and user-meal interaction from the user's dining sessions simulated based on user-course interaction data. Then, two well-known nutritional standards are used to calculate the healthiness scores of meals. Moreover, we experiment with several baseline models, including separate and cooperative interaction learning methods. Our experiment demonstrates that cooperating the two levels of interaction in appropriate ways is beneficial for meal recommendations. The dataset is available on GitHub (https://github.com/WUT-IDEA/MealRecPlus).

Food computing, a newly emerging topic, is closely linked to human life through computational methodologies. Meal recommendation, a food-related study about human health, aims to provide users a meal with courses constrained from specific categories (e.g., appetizers, main dishes) that can be enjoyed as a service. Historical interaction data, important user information, is often used by existing models to learn user preferences. However, if a user’s preferences favor less healthy meals, the model will follow that preference and make similar recommendations, potentially negatively impacting the user’s long-term health. This emphasizes the necessity for health-oriented and responsible meal recommendation systems. In this article, we propose a healthiness-aware and category-wise meal recommendation model called CateRec, which boosts healthiness exposure by using nutritional standards as knowledge to guide the model training. Two fundamental questions are raised and answered: (1) How can the healthiness of meals be evaluated? Two well-known nutritional standards from the World Health Organization and the United Kingdom Food Standards Agency are used to calculate the healthiness score of the meal. (2) How can the model training be guided in a health-oriented manner? We construct category-wise personalization partial rankings and category-wise healthiness partial rankings, and theoretically analyze that they meet the necessary properties and assumptions required to be trained by the maximum posterior estimator under Bayesian probability. The data analysis confirms the existence of user preferences leaning towards less healthy meals in two public datasets. A comprehensive experiment demonstrates that our CateRec effectively boosts healthiness exposure in terms of mean healthiness score and ranking exposure while being comparable to the state-of-the-art model in terms of recommendation accuracy.

Cross-modal retrieval technology can help people quickly achieve mutual information between cooking recipes and food images. Both the embeddings of the image and the recipe consist of multiple representation subspaces. We argue that multiple aspects in the recipe are related to multiple regions in the food image. It is challenging to improve the cross-modal retrieval quality by making full use of the implicit connection between multiple subspaces of recipes and images. In this paper, we propose a multi-subspace implicit alignment cross-modal retrieval framework of recipes and images. Our framework learns multi-subspace information about cooking recipes and food images with multi-head attention networks; the implicit alignment at the subspace level promotes narrowing the semantic gap between recipe embeddings and food image embeddings; triple loss and adversarial loss are combined to help our framework for cross-modal learning. The experimental results show that our framework significantly outperforms to state-of-the-art methods in terms of MedR and [email protected] on Recipe 1M.