Locality Sensitive Hashing in Fourier Frequency Domain For Soft Set Containment Search

In many search applications related to passage retrieval, text entailment, and subgraph search, the query and each'document' is a set of elements, with a document being relevant if it contains the query. These elements are not represented by atomic IDs, but by embedded representations, thereby extending set containment to soft set containment. Recent applications address soft set containment by encoding sets into fixed-size vectors and checking for elementwise vector dominance. This 0/1 property can be relaxed to an asymmetric hinge distance for scoring and ranking candidate documents. Here we focus on data-sensitive, trainable indices for fast retrieval of relevant documents. Existing LSH methods are designed for mostly symmetric or few simple asymmetric distance functions, which are not suitable for hinge distance. Instead, we transform hinge distance into a proposed dominance similarity measure, to which we then apply a Fourier transform, thereby expressing dominance similarity as an expectation of inner products of functions in the frequency domain.