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XLingDocModel.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
 *
 *==========================================================================
*/


#ifndef _XLINGDOCMODEL_HPP
#define _XLINGDOCMODEL_HPP

#include "RetrievalMethod.hpp"
#include "Index.hpp"
#include "DocumentRep.hpp"

class XLingDocModel : public DocumentRep {
public:
  XLingDocModel(DOCID_T docID, const Index *ind, double l, double nt, 
                bool sM = false) :
    DocumentRep(docID, ind->docLength(docID)), refIndex(ind), lambda(l), 
                                 numTerms(nt),  docBasedSmooth(sM) {
  };
  
  ~XLingDocModel() {};
  virtual double termWeight(TERMID_T termID, const DocInfo *info) const {
    //    double p_doc = info->termCount()/(double)refIndex->docLength(id);
    double p_doc = info->termCount()/(double)docLength;
    double p_gen; 
    if (docBasedSmooth) 
      p_gen = refIndex->docCount(termID)/numTerms;
    else 
      p_gen = refIndex->termCount(termID)/numTerms;
    return ((lambda * p_doc) + ((1 - lambda) * p_gen));
  }

  virtual double scoreConstant() const {
    return lambda;
  }

protected:
  const Index *refIndex;
  double numTerms;
  double lambda;
  bool docBasedSmooth;
};

#endif /* _XLINGDOCMODEL_HPP */

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