UFRGS@CLEF2009: Retrieval by Numbers

For UFRGS’s participation on CLEF’s Robust task, our aim was to compare retrieval of plain documents to retrieval using information on word senses. The experimental run which used word-sense disambiguation (WSD) consisted in indexing the synset codes of the senses which had scores higher than a predefined threshold. The documents in both baseline and WSD runs were indexed by Zettair. The metric for comparing queries and documents was OkapiBM25. The results of the experiments show that only 47 topics were helped by the strategy, while 103 had their performances worsened. A statistical t-test has shown that the experimental run which did not use WSD information significantly outperformed the one which did. A deeper analysis of our results and a set of further experiments are now under preparation.