Relevance Ranking Using Terms TF-IDF (Term frequency/Inverse Document frequency)ranking: Let n(d)=number of terms in the document d n(d,)number of occurrences ofterm t in the document d. Relevance of a document d to a term t n(d,t) TF (d,t)=log 1+ n(d) The log factor is to avoid excessive weight to frequent terms Relevance of document to query Q r(d,Q)=∑ TF(d.t) t∈Q n(t) Database System Concepts-7th Edition 31.6 @Silberschatz,Korth and SudarshanDatabase System Concepts - 7 31.6 ©Silberschatz, Korth and Sudarshan th Edition 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)