Computing Scores in a Complete Search System Recap: tf-idf weighting The tf-idf weight of a term is the product of its tf weight and its idf weight W,=(1+log tf, d)logo(N/df, Best known weighting scheme in information retrieval Increases with the number of occurrences within a document a Increases with the rarity of the term in the collectionComputing Scores in a Complete Search System Recap: tf-idf weighting ▪ The tf-idf weight of a term is the product of its tf weight and its idf weight. ▪ Best known weighting scheme in information retrieval ▪ Increases with the number of occurrences within a document ▪ Increases with the rarity of the term in the collection w (1 log tf ) log ( /df ) , t,d 10 N t t d = +  2