Hierarchical Hyperedge Embedding-based Representation Learning for Group Recommendation

Abstract

Group Recommendation (GR) aims to recommend items to a group of users. In this work, we study GR in a particular scenario, namely Occasional Group Recommendation (OGR), where groups are formed ad-hoc and users may just constitute a group for the first time, that is, the historical group-item interaction records are highly limited. Most state-of-the-art works have addressed the challenge by aggregating group members' personal preferences to learn the group representation. However, the representation learning for a group is most complex beyond the aggregation or fusion of group member representation, as the personal preferences and group preferences may be in different spaces and even orthogonal. In addition, the learned user representation is not accurate due to the sparsity of users' interaction data. Moreover, the group similarity in terms of common group members has been overlooked, which however has the great potential to improve the group representation learning. In this work, we focus on addressing the aforementioned challenges in group representation learning task, and devise a hierarchical hyperedge embedding-based group recommender, namely HyperGroup. Specifically, we propose to leverage the user-user interactions to alleviate the sparsity issue of user-item interactions, and design a Graph Neural Network (GNN)-based representation learning network to enhance the learning of individuals' preferences from their friends' preferences, which provides a solid foundation for learning groups' preferences. To exploit the group similarity (i.e., overlapping relationships among groups) to learn a more accurate group representation from highly limited group-item interactions, we connect all groups as a network of overlapping sets (a.k.a. hypergraph), and treat the task of group preference learning as embedding hyperedges (i.e., user sets/groups) in a hypergraph, where an inductive hyperedge embedding method is proposed. To further enhance the group-level preference modeling, we develop a joint training strategy to learn both user-item and group-item interactions in the same process. We conduct extensive experiments on two real-world datasets and the experimental results demonstrate the superiority of our proposed HyperGroup in comparison to the state-of-the-art baselines.

Hypergraph Convolutional Network for Group Recommendation

“…Guo et al [31] proposes a GNN-based model for group recommendation, which leverages friends' preference from the social network and connects group members as hyperedge to aggregate group preference. This method concentrates on utilize side information and aggregate member interest while ignores explicitly modeling the group's general preference.…”