A Single Vector Is Not Enough: Taxonomy Expansion via Box Embeddings (Extended Abstract)

Taxonomies support various practical web applications such as product navigation in online shopping and user profile tagging on social platforms. Most existing methods for expanding taxonomies encode entities into vector embeddings (i.e., single points). However, we argue that vectors are insufficient to model the ``is-a'' hierarchy in taxonomy (asymmetrical relation), because two points can only represent pairwise similarity (symmetrical relation). To this end, we propose to project taxonomy entities into boxes (i.e., hyperrectangles). Two boxes can be "contained", "disjoint" and "intersecting", thus naturally representing an asymmetrical taxonomic hierarchy. Upon box embeddings, we propose a novel model BoxTaxo for taxonomy expansion. The core of BoxTaxo is to learn boxes for entities to capture their child-parent hierarchies. Extensive experiments on two benchmarks demonstrate the effectiveness of BoxTaxo compared to vector based models.