International audienceFollowing our previous participation in INEX 2008 Ad-hoc track, we continue to address both standard and focused retrieval tasks based on comprehensible language models and interactive query expansion (IQE). Query topics are expanded using an initial set of Multiword Terms (MWTs) selected from top n ranked documents. In this experiment, we extract MWTs from article titles, narrative field and automatically generated summaries. We combined the initial set of MWTs obtained in an IQE process with automatic query expansion (AQE) using language models and smoothing mechanism. We chose as baseline the Indri IR engine based on the language model using Dirichlet smoothing. We also compare the performance of bag of word approaches (TFIDF and BM25) to search strategies elaborated using language model and query expansion (QE). The experiment is carried out on all INEX 2009 Ad-hoc tasks
