  In this work, we study group recommendation in a particular scenario, namely
Occasional Group Recommendation (OGR). Most existing works have addressed OGR
by aggregating group members' personal preferences to learn the group
representation. However, the representation learning for a group is most
complex beyond the fusion of group member representation, as the personal
preferences and group preferences may be in different spaces. 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
above 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 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 to learn a
more accurate group representation from highly limited group-item interactions,
we connect all groups as a network of overlapping sets, and treat the task of
group preference learning as embedding hyperedges 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.
