Passage retrieval revisited

Abstract

Ranking based on passages addresses some of the shortcomings of whole-document ranking. It provides convenient units of text to return to the user, avoids the difficulties of comparing documents of different length, and enables identification of short blocks of relevant material amongst otherwise irrelevant text. In this paper we explore the potential of passage retrieval, based on an experimental evaluation of the ability of passages to identify relevant documents. We compare our scheme of arbitrary passage retrieval to several other document retrieval and passage retrieval methods; we show experimentally that, compared to these methods, ranking via fixed-length passages is robust and effective. Our experiments also show that, compared to whole-document ranking, ranking via fixed-length arbitrary passages significantly improves retrieval effectiveness, by 8% for TREC disks 2 and 4 and by 18%-37% for the Federal Register collection.