Okapi at TREC-4

Okapi at TREC-5

City submitted two runs each for the automatic ad hoc, very large collection track, automatic routing and Chinese track; and took part in the interactive and ltering tracks. There were no very signi cant new developments; the same Okapi-style weighting as in TREC{3 and TREC{4 was used this time round, although there were attempts, in the ad hoc and more notably in the Chinese experiments, to ex...

UCLA-Okapi at TREC-2: Query Expansion Experiments

This is the rst participation of the Graduate School of Library and Information Science, University of California at Los Angeles in the TREC Conference. For TREC{2, Category B, UCLA used a version of the Okapi text retrieval system that was made available to UCLA by City University, London, UK. OKAPI has been described in TREC1 (Robertson, Walker, Hancock-Beaulieu, Gull & Lau, 1993a) as well as...

Okapi at TREC { 4 S E Robertson

Okapi at Trecc6 Automatic Ad Hoc, Vlc, Routing, Ltering and Qsdr Note on Notation

Many experiments were concerned with \blind" expansion (i.e. expansion using pseudo-relevant and -nonrelevant documents). A very large number of runs were done on TREC{3, 4 and 5 data to investigate the e ect of varying the Okapi BM25 parameters on precision at low recall. Methods of selecting and ranking topic terms and expansion terms were investigated. In particular, introducing a \non-relev...

Okapi at TREC-2

This paper reports on City University's work on the TREC{2 project from its commencement up to November 1993. It includes many results which were obtained after the August 1993 deadline for submission of o cial results. For TREC{2, as for TREC{1, City University used versions of the Okapi text retrieval system much as described in [2] (see also [3, 4]). Okapi is a simple and robust set-oriented...