Variational autoencoder (VAE) is known as a classic and effective method in modeling users’ homogeneous behaviors in recommender systems. In recent years, graph neural networks (GNNs) have achieved promising performance in learning users’ preferences by modeling complex relationships between users and items. However, most VAE- and GNN-based methods are for single-behavior recommendation, rather than the more prevalent counterpart in real-world applications, i.e., multi-behavior recommendation. This motivates us to leverage VAE and GNNs to address the more important and challenging problem of multi-behavior recommendation. Traditional multi-behavior recommendation models have not captured the complex transition relationships across different types of behaviors well. Moreover, they often ignore the varying semantic strength of different types of behaviors. To tackle the above two challenges, we propose a novel multi-behavior recommendation framework named VCGAE (short for Variational Collective Graph AutoEncoder), which inherits the advantages of VAE and GNNs to fully exploit the multi-behavior data. Specifically, we design a behavior transition network that considers different transition relationships across different types of behaviors in order to learn users’ personal preferences. In addition, we introduce a behavior contrastive regularization module that extracts different correlations between users’ auxiliary behaviors and target behavior. By doing so, we gain a deeper understanding of the semantic strength of different behaviors, thereby improving the overall recommendation performance. Extensive experiments on three real-world datasets clearly demonstrate the effectiveness of our VCGAE compared with the state-of-the-art methods.

A practical recommender system should be able to handle heterogeneous behavioral feedback as inputs and has multi-task outputs ability. Although the heterogeneous one-class collaborative filtering (HOCCF) and multi-task learning (MTL) methods has been well studied, there is still a lack of targeted manner in their combined fields, i.e., Multi-behavior Multi-task Recommendation (MMR). To fill the gap, we propose a novel recommendation framework called Behavior-aware Variational AutoEncoder (BVAE), which meliorates the parameter sharing and loss minimization method with the VAE structure to address the MMR problem. Specifically, our BVAE includes behavior-aware semi-encoders and decoders, and a target feature fusion network with a global feature filtering network, while using standard deviation to weigh loss. These modules generate the behavior-aware recommended item list via constructing better semantic feature vectors for users, i.e., from dual perspectives of behavioral preference and global interaction. In addition, we optimize our BVAE in terms of adaptability and robustness, i.e., it is concise and flexible to consume any amount of behaviors with different distributions. Extensive empirical studies on two real and widely used datasets confirm the validity of our design and show that our BVAE can outperform the state-of-the-art related baseline methods under multiple evaluation metrics. The processed datasets, source code, and scripts necessary to reproduce the results can be available at https://github.com/WitnessForest/BVAE.