When less is more: Relevance feedback falls short and term expansion succeeds at HARD 2005

We used clarification forms to study passage term feedback. When compared against pseudo-relevance feedback with an extremely large external corpus, we found that passage feed-back resulted in a reduction in performance while term feed-back significantly improved recall. 1. OVERVIEW UMass tested several new techniques in the HARD track this year. First, we developed a new baseline pseudo-relevance feedback technique based on expanding from a large, exter-nal corpus [6]. Our results indicate that externally expand-ing a query can result in improvements over passage feed-back. Second, we present a new feedback technique which incorporates both relevance and non-relevance information. Our results indicate that this regularization-based techniqu