Relevance Ranking Using Terms TF-IDF(Term frequency/Inverse Document frequency)ranking: Let n(d)=number of terms in the document d n(d,t)=number of occurrences of term t in the document d. Relevance of a document d to a term t n(d,t) TF (d,t)=log I+m(d) The log factor is to avoid excessive weight to frequent terms Relevance of document to query Q r (d,C)= TF(d.t tEO n(t) Database System Concepts-5th Edition,Sep 2,2005 19.6 @Silberschatz,Korth and SudarshanDatabase System Concepts - 5 19.6 ©Silberschatz, Korth and Sudarshan th Edition, Sep 2, 2005 Relevance Ranking Using Terms TF-IDF (Term frequency/Inverse Document frequency) ranking: Let n(d) = number of terms in the document d n(d, t) = number of occurrences of term t in the document d. Relevance of a document d to a term t  The log factor is to avoid excessive weight to frequent terms Relevance of document to query Q n(d) n(d, t) TF (d, t) = log 1 + r (d, Q) =  TF (d, t) tQ n(t)