Disentangled Representation Learning (DRL) aims to learn a model capable of identifying and disentangling the underlying factors hidden in the observable data in representation form. The process of separating underlying factors of variation into variables with semantic meaning benefits in learning explainable representations of data, which imitates the meaningful understanding process of humans when observing an object or relation. As a general learning strategy, DRL has demonstrated its power in improving the model explainability, controlability, robustness, as well as generalization capacity in a wide range of scenarios such as computer vision, natural language processing, and data mining. In this article, we comprehensively investigate DRL from various aspects including motivations, definitions, methodologies, evaluations, applications, and model designs. We first present two well-recognized definitions, i.e., Intuitive Definition and Group Theory Definition for disentangled representation learning. We further categorize the methodologies for DRL into four groups from the following perspectives, the model type, representation structure, supervision signal, and independence assumption. We also analyze principles to design different DRL models that may benefit different tasks in practical applications. Finally, we point out challenges in DRL as well as potential research directions deserving future investigations. We believe this work may provide insights for promoting the DRL research in the community.

Sequential recommender systems often suffer from performance drops due to the data-sparsity issue in real-world scenarios. To address this issue, we bravely take advantage of the strength in diffusion model to conduct data augmentation for sequential recommendation in this paper. However, there remain two critical challenges for this scarcely-explored topic: (i) previous diffusion models are mostly designed for image generation aiming to capture pixel patterns, which can hardly be applied in data augmentation for sequential recommendation aiming to capture the user-item relations; (ii) given a specific diffusion model capable of user-item interaction augmentation, it is non-trivial to guarantee that the diffusion-generated data can always bring benefits towards the sequential recommendation model. To tackle these challenges, we propose Diff4Rec, a curriculum-scheduled diffusion augmentation framework for sequential recommendation. Specifically, a diffusion model is pre-trained on recommendation data via corrupting and reconstructing the user-item interactions in the latent space, and the generated predictions are leveraged to produce diversified augmentations for the sparse user-item interactions. Subsequently, a curriculum scheduling strategy is designed to progressively feed the diffusion-generated samples into the sequential recommenders, with respect to two levels, i.e., interaction augmentation and objective augmentation, to jointly optimize the data and model. Extensive experiments demonstrate that our proposed Diff4Rec framework is able to effectively achieve superior performance over several strong baselines, capable of making high-quality and robust sequential recommendations. We believe the proposed Diff4Rec has the promising potential to bring paradigm shift in multimedia recommendation.

Video Grounding (VG), has drawn widespread attention over the past few years, and numerous studies have been devoted to improving performance on various VG benchmarks. Nevertheless, the label annotation procedures in VG produce imbalanced query-moment-label distributions in the datasets, which severely deteriorate the learning model's capability of truly understanding the video contents. Existing works on debiased VG either focus on adjusting the learning model or conducting video-level augmentation, failing to handle the temporal bias issue caused by imbalanced query-moment-label distributions. In this paper, we propose a Disentangled Feature Mixup (DFM) framework for debiased VG, which is capable of performing unbiased grounding to tackle the temporal bias issue. Specifically, a feature-mixup augmentation strategy is designed to generate new (text, location) pairs with diverse temporal distributions via jointly augmenting the representation of text queries and the location labels. This strategy encourages making prediction based on more diverse data samples with balanced query-moment-label distributions. Furthermore, we also design a content-location disentanglement module to disentangle the representations of the temporal information and content information in videos, which is able to remove the spurious effect of temporal biases on video representation. Given that our proposed DFM framework conducts feature-level augmentation and disentanglement, it is model-agnostic and can be applied to most baselines simply yet effectively. Extensive experiments show that our proposed DFM framework is able to significantly outperform baseline models in various metrics under both independent identical distribution (i.i.d.) and out-of-distribution (o.o.d.) scenes, especially in scenarios with annotation distribution changes.