Prédire la difficulté des requêtes : la combinaison de mesures statistiques et sémantiques

The performance of an Information Retrieval System (IRS) is closely related to the query. The queries that lead to retrieval failure are referenced in the literature as "difficult queries". This study aims at analysing, adapting and combining several difficulty predictors. The evaluation of the prediction is based on the correlation between the predicted difficulty and the IRS performance. As predictors, we have considered an ambiguity predictor, the IDF measure and a score distribution measure. We show that combining the proposed predictors, produce good results. The evaluation framework consists in the TREC7 and TREC8 ahdoc collections. MOTS-CLÉS : Recherche d’Information, prédire la performance, difficulté des requêtes, ambiguïté des requêtes, combinaison des prédicteurs, corrélation des mesures