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QueryExpander.hpp

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/*==========================================================================
 * Copyright (c) 2004 University of Massachusetts.  All Rights Reserved.
 *
 * Use of the Lemur Toolkit for Language Modeling and Information Retrieval
 * is subject to the terms of the software license set forth in the LICENSE
 * file included with this software, and also available at
 * http://www.lemurproject.org/license.html
 *
 *==========================================================================
*/

//
// QueryExpander
//
// 18 Aug 2004 -- dam
//

#ifndef INDRI_QUERYEXPANDER_HPP
#define INDRI_QUERYEXPANDER_HPP

#include <string>
#include <vector>
#include <map>

#include "indri/QueryEnvironment.hpp"
#include "indri/Parameters.hpp"

struct QueryExpanderSort {
public:
  bool operator() ( const std::pair<std::string, double>& one, const std::pair<std::string, double>& two ) const {
    return one.second > two.second;
  }
};

class QueryExpander {
private:
  std::map<std::string, int> _cf_cache;
  
protected:
  QueryEnvironment * _env;
  Parameters _param;

  std::vector<DocumentVector*> getDocumentVectors( std::vector<ScoredExtentResult>& results, int rmDocs );
  std::vector<std::string> * getVocabulary( std::vector<ScoredExtentResult>& results, int rmDocs );
  std::vector<std::string> * getVocabulary( std::vector<DocumentVector*>& docVectors );
  int getCF( std::string term );
  
public:
  QueryExpander( QueryEnvironment * env , Parameters& param );
  virtual ~QueryExpander() {};

  // runs original query, expands query based on results ( via expand( .. ) ), then runs expanded query
  std::vector<ScoredExtentResult> runExpandedQuery( std::string originalQuery , int resultsRequested , bool verbose = false );
  
  // creates expanded query from an original query and a ranked list of documents
  virtual std::string expand( std::string originalQuery , std::vector<ScoredExtentResult>& results ) = 0;
};

#endif

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