Inverted files 
  Signature files 
  New indices for text: PAT trees and arrays 
  Lexical analysis and stoplists 
  Stemming algorithms 
  Thesaurus construction 
  String searching algorithms 
  Relevance feedback and other query modification techniques 
  Boolean operations 
  Hashing algorithms 
  Ranking algorithms 
  Extended Boolean models 
  Clustering algorithms 
   
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