LiRME: Locally interpretable ranking model explanation

Abstract

Information retrieval (IR) models often employ complex variations in term weights to compute an aggregated similarity score of a query-document pair. Treating IR models as black-boxes makes it difficult to understand or explain why certain documents are retrieved at top-ranks for a given query. Local explanation models have emerged as a popular means to understand individual predictions of classification models. However, there is no systematic investigation that learns to interpret IR models, which is in fact the core contribution of our work in this paper. We explore three sampling methods to train an explanation model and propose two metrics to evaluate explanations generated for an IR model. Our experiments reveal some interesting observations, namely that a) diversity in samples is important for training local explanation models, and b) the stability of a model is inversely proportional to the number of parameters used to explain the model.