An evaluation of passage-level indexing strategies for a technical report archive

Past research has shown that using evidence from document passages rather than complete documents is an effective way of improving the precision of full-text database searches. However, passage-level indexing has yet to be widely adopted for commercial or online databases. This paper reports on experiments designed to test the efficacy of passage-level indexing with a particular collection of a full-text online database, the New Zealand Digital Library. Discourse passages and word-window passages are used for the indexing process. Both ranked and Boolean searching are used to test the resulting indexes. Overlapping window passages are shown to offer the best retrieval performance with both ranked and Boolean queries. Modifications may be necessary to the term weighting methodology in order to ensure optimal ranked query performance