Lost in translation? An Empirical Study of the use of Thesauri in Query Expansion in Cross Language Information Retrieval

The purpose of this thesis is to examine the performance of queries that is expanded before translation in comparison with only translation of the queries using a bilingual dictionary, and also to see if the number of terms that was used to expand the queries was of any importance i. e. if many terms from a thesaurus helped or destroyed a query. To answer these questions i used two online thesauri, Rogets thesaurus and Merriam-Webster Online and one printed bilingual dictionary, Norstedts English-Swedish dictionary. Even though the number of examined queries is too small to draw any definite conclusions, the results suggest that expanding using a general thesaurus may have a negative effect on the queries. The reason is that the number of words from the expansion and the translation makes the queries more ambiguous and thereby increases the noise in the search, which leads to loss of relevant document.Uppsatsnivå: