Akin to Xiong et al., 2017;, the NIRM baselines and the proposed NPRF are employed to re-rank the search results from BM25.
the top-10 documents from the unsupervised baseline are used as the pseudo relevance feedback documents D q as input for NPRF, where each d q ∈ D q is represented by its top-20 terms with the highest tfidf weights.