Ad Hoc Retrieval with the Persian Language

This paper describes our participation to the Persian <i>ad hoc</i> search during the CLEF 2009 evaluation campaign. In this task, we suggest using a light suffix-stripping algorithm for the Farsi (or Persian) language. The evaluations based on different probabilistic models demonstrated that our stemming approach performs better than a stemmer removing only the plural suffixes, or statistically better than an approach ignoring the stemming stage (around +4.5%) or a <i>n</i>-gram approach (around +4.7%). The use of a blind query expansion may significantly improve the retrieval effectiveness (between +7% to +11%). Combining different indexing and search strategies may further enhance the MAP (around +4.4%).