Information retrieval system using a hierarchical corpus encoder

A dense encoder is adapted as a hierarchical corpus encoder in an information retrieval system to use negative samples from sibling nodes in a hierarchical tree of vector embeddings for documents in a corpus. Both the encoder and hierarchical tree are co-trained using a loss function that takes the document hierarchy into account. The hierarchical corpus encoder may be used in both supervised training cases where query-document relevance judgments are present and in zero-shot cases where a query dataset is absent.