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Keyword Search In full text retrieval,all the words in each document are considered to be keywords. We use the word term to refer to the words in a document Information-retrieval systems typically allow query expressions formed using keywords and the logical connectives and,or,and not Ands are implicit,even if not explicitly specified Ranking of documents on the basis of estimated relevance to a query is critical Relevance ranking is based on factors such as Term frequency -Frequency of occurrence of query keyword in document Inverse document frequency How many documents the query keyword occurs in 》Fewer→give more importance to keyword Hyperlinks to documents -More links to a document>document is more important Database System Concepts-6th Edition 21.5 @Silberschatz,Korth and SudarshanDatabase System Concepts - 6 21.5 ©Silberschatz, Korth and Sudarshan th Edition Keyword Search In full text retrieval, all the words in each document are considered to be keywords. We use the word term to refer to the words in a document Information-retrieval systems typically allow query expressions formed using keywords and the logical connectives and, or, and not Ands are implicit, even if not explicitly specified Ranking of documents on the basis of estimated relevance to a query is critical Relevance ranking is based on factors such as  Term frequency – Frequency of occurrence of query keyword in document  Inverse document frequency – How many documents the query keyword occurs in » Fewer ➔ give more importance to keyword  Hyperlinks to documents – More links to a document ➔ document is more important
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