Y. Bernstein, B. Billerbeck, S. Garcia, N. Lester, F. Scholer, J. Zobel, and W. Webber
RMIT University participated in the terabyte and robust tracks in TREC 2005. The terabyte track consists of the three tasks: adhoc retrieval, efficient retrieval, and named page finding. For the adhoc retrieval task we used a language modelling approach based on query likelihood, as well as a new technique aimed at reducing the amount of memory used for ranking documents. For the efficiency task, we submitted results from both a single-machine system and one that was distrubuted among a number of machines, with promising results. The named page task was organised by RMIT University and as a result we repeated last year's experiments, slightly modified, with this year's data. The robust track has two subtasks: adhoc retrieval, and query difficulty prediction. For adhoc retrieval, we employed a standard local analysis query expansion method, sourcing expansion terms for different runs from the collection supplied, from a side corpus, or a combination of both. In one run, we also tested removing duplicate documents from the list of results. In order to predict topic difficulty, we evaluated different document priors of the documents in the result set, in the hope of supplying a more robust set of answers at the cost of returning a potentially smaller number of relevant documents. The second task was to predict query difficulty. To this end, we compared the order of the documents in the result sets to the ordering as determined by document priors. A high similarity in orderings indicated that the query was poor. Two different priors were used. The first was based on document access counts, where each document is given a score that is derived from how likely it is to be ranked by a randomly generated query. The second was directly related to the document size. In this paper we outline our approaches and experiments in both tracks, and discuss our results.
In Proceedings Text Retrieval Conference (TREC)
Publisher National Institute of Standards and Technology
All copyrights reserved by NIST 2005.