Terrier IR Platform
1.1.1

uk.ac.gla.terrier.structures
Class ExpansionTerms

java.lang.Object
  extended by uk.ac.gla.terrier.structures.ExpansionTerms

public class ExpansionTerms
extends java.lang.Object

This class implements a data structure of terms in the top-retrieved documents.

Properties:

Version:
$Revision: 1.37 $
Author:
Gianni Amati, Ben He, Vassilis Plachouras, Craig Macdonald

Nested Class Summary
 class ExpansionTerms.ExpansionTerm
          This class implements a data structure for a term in the top-retrieved documents.
 
Field Summary
 double normaliser
          The parameter-free term weight normaliser.
 
Constructor Summary
ExpansionTerms(CollectionStatistics collStats, double totalLength, Lexicon lexicon)
          Constructs an instance of ExpansionTerms.
ExpansionTerms(int numberOfDocuments, long numberOfTokens, double averageDocumentLength, double totalLength, Lexicon lexicon)
          Constructs an instance of ExpansionTerms.
 
Method Summary
 void assignWeights(QueryExpansionModel QEModel)
          Assign weight to terms that are stored in ExpansionTerm[] terms.
 void deleteTerm(int termid)
          Remove the records for a given term
 double getDocumentFrequency(int termId)
          Returns the number of the top-ranked documents a given term occurs in.
 SingleTermQuery[] getExpandedTerms(int numberOfExpandedTerms, QueryExpansionModel QEModel)
          This method implements the functionality of assigning expansion weights to the terms in the top-retrieved documents, and returns the most informative terms among them.
 double getExpansionProbability(int termId)
          Returns the probability of a given termid occurring in the expansion documents.
 double getExpansionWeight(int termId)
          Returns the weight of a term with the given term identifier.
 double getExpansionWeight(int termId, QueryExpansionModel model)
          Returns the weight of a term with the given term identifier, computed by the specified query expansion model.
 double getExpansionWeight(java.lang.String term)
          Returns the weight of a given term.
 double getExpansionWeight(java.lang.String term, QueryExpansionModel model)
          Returns the weight of a given term, computed by the specified query expansion model.
 double getFrequency(int termId)
          Returns the frequency of a given term in the top-ranked documents.
 double getFrequency(java.lang.String term)
          Returns the frequency of a given term in the top-ranked documents.
 int getNumberOfUniqueTerms()
          Returns the unique number of terms found in all the top-ranked documents
 double getOriginalExpansionWeight(java.lang.String term)
          Returns the un-normalised weight of a given term.
 int[] getTermIds()
          Returns the termids of all terms found in the top-ranked documents
 void insertTerm(int termID, double withinDocumentFrequency)
          Add a term in the X top-retrieved documents as a candidate of the expanded terms.
 void setOriginalQueryTerms(MatchingQueryTerms query)
          Set the original query terms.
 void setTotalDocumentLength(double totalLength)
          Allows the totalDocumentLength to be set after the fact
 
Methods inherited from class java.lang.Object
equals, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait
 

Field Detail

normaliser

public double normaliser
The parameter-free term weight normaliser.

Constructor Detail

ExpansionTerms

public ExpansionTerms(CollectionStatistics collStats,
                      double totalLength,
                      Lexicon lexicon)
Constructs an instance of ExpansionTerms.

Parameters:
totalLength - The sum of the length of the top-retrieved documents.
lexicon - Lexicon The lexicon used for retrieval.

ExpansionTerms

public ExpansionTerms(int numberOfDocuments,
                      long numberOfTokens,
                      double averageDocumentLength,
                      double totalLength,
                      Lexicon lexicon)
Constructs an instance of ExpansionTerms.

Parameters:
totalLength - The sum of the length of the top-retrieved documents.
lexicon - Lexicon The lexicon used for retrieval.
Method Detail

setTotalDocumentLength

public void setTotalDocumentLength(double totalLength)
Allows the totalDocumentLength to be set after the fact


getTermIds

public int[] getTermIds()
Returns the termids of all terms found in the top-ranked documents


getNumberOfUniqueTerms

public int getNumberOfUniqueTerms()
Returns the unique number of terms found in all the top-ranked documents


getExpandedTerms

public SingleTermQuery[] getExpandedTerms(int numberOfExpandedTerms,
                                          QueryExpansionModel QEModel)
This method implements the functionality of assigning expansion weights to the terms in the top-retrieved documents, and returns the most informative terms among them. Conservative Query Expansion (ConservativeQE) is used if the number of expanded terms is set to 0. In this case, no new query terms are added to the query, only the existing ones reweighted.

Parameters:
numberOfExpandedTerms - int The number of terms to extract from the top-retrieved documents. ConservativeQE is set if this parameter is set to 0.
QEModel - QueryExpansionModel the model used for query expansion
Returns:
TermTreeNode[] The expanded terms.

setOriginalQueryTerms

public void setOriginalQueryTerms(MatchingQueryTerms query)
Set the original query terms.

Parameters:
query - The original query.

deleteTerm

public void deleteTerm(int termid)
Remove the records for a given term


getExpansionWeight

public double getExpansionWeight(java.lang.String term,
                                 QueryExpansionModel model)
Returns the weight of a given term, computed by the specified query expansion model.

Parameters:
term - String the term to set the weight for.
model - QueryExpansionModel the used query expansion model.
Returns:
double the weight of the specified term.

getExpansionWeight

public double getExpansionWeight(java.lang.String term)
Returns the weight of a given term.

Parameters:
term - String the term to get the weight for.
Returns:
double the weight of the specified term.

getOriginalExpansionWeight

public double getOriginalExpansionWeight(java.lang.String term)
Returns the un-normalised weight of a given term.

Parameters:
term - String the given term.
Returns:
The un-normalised term weight.

getFrequency

public double getFrequency(java.lang.String term)
Returns the frequency of a given term in the top-ranked documents.

Parameters:
term - String the term to get the frequency for.
Returns:
double the frequency of the specified term in the top-ranked documents.

getFrequency

public double getFrequency(int termId)
Returns the frequency of a given term in the top-ranked documents.

Parameters:
termId - int the id of the term to get the frequency for.
Returns:
double the frequency of the specified term in the top-ranked documents.

getDocumentFrequency

public double getDocumentFrequency(int termId)
Returns the number of the top-ranked documents a given term occurs in.

Parameters:
termId - int the id of the term to get the frequency for.
Returns:
double the document frequency of the specified term in the top-ranked documents.

assignWeights

public void assignWeights(QueryExpansionModel QEModel)
Assign weight to terms that are stored in ExpansionTerm[] terms.

Parameters:
QEModel - QueryExpansionModel the used query expansion model.

getExpansionWeight

public double getExpansionWeight(int termId,
                                 QueryExpansionModel model)
Returns the weight of a term with the given term identifier, computed by the specified query expansion model.

Parameters:
termId - int the term identifier to set the weight for.
model - QueryExpansionModel the used query expansion model.
Returns:
double the weight of the specified term.

getExpansionWeight

public double getExpansionWeight(int termId)
Returns the weight of a term with the given term identifier.

Parameters:
termId - int the term identifier to set the weight for.
Returns:
double the weight of the specified term.

getExpansionProbability

public double getExpansionProbability(int termId)
Returns the probability of a given termid occurring in the expansion documents. Returns the quotient document frequency in the expansion documents, divided by the total length of all the expansion documents.

Parameters:
termId - int the term identifier to obtain the probability
Returns:
double the probability of the term

insertTerm

public void insertTerm(int termID,
                       double withinDocumentFrequency)
Add a term in the X top-retrieved documents as a candidate of the expanded terms.

Parameters:
termID - int the integer identifier of a term
withinDocumentFrequency - double the within document frequency of a term

Terrier IR Platform
1.1.1

Terrier Information Retrieval Platform 1.1.1. Copyright 2004-2007 University of Glasgow