Thomson Legal and Regulatory Experiments at CLEF-2005

Abstract

For the 2005 Cross-Language Evaluation Forum, Thomson Legal and Regulatory participated in the Hungarian, French, and Portuguese monolingual search tasks as well as French-to-Portuguese bilingual retrieval. Our Hungarian participation focused on comparing the effectiveness of different approaches toward morphological stemming. Our French and Portuguese monolingual efforts focused on different approaches to Pseudo-Relevance Feedback (PRF), in particular the evaluation of a scheme for selectively applying PRF only in the cases most likely to produce positive results. Our French-to-Portuguese bilingual effort applies our previous work in query translation to a new pair of languages and uses corpus-based language modeling to support term-by-term translation. We compare our approach to an off-the-self machine translation system that translates the query as a whole and find the latter approach to be more performant. All experiments were performed using our proprietary search engine. We remain encouraged by the overall success of our efforts, with our main submissions for each of the four tasks performing above the overall CLEF median. However, none of the specific enhancement techniques we attempted in this year’s forum showed significant improvements over our initial result.