org.terrier.matching.tsms
Class RequiredTermModifier

java.lang.Object
  org.terrier.matching.models.WeightingModel
      org.terrier.matching.tsms.RequiredTermModifier

All Implemented Interfaces:

java.io.Serializable, java.lang.Cloneable, Model, TermScoreModifier

public class RequiredTermModifier
extends WeightingModel
implements TermScoreModifier, java.io.Serializable

Resets the scores of documents according to whether a term is required or not, and whether it appears in the retrieved documents. This class implements the TermScoreModifier interface.

Author:

Vassilis Plachouras

See Also:

Serialized Form

Field Summary

Fields inherited from class org.terrier.matching.models.WeightingModel

averageDocumentLength, c, documentFrequency, i, keyFrequency, numberOfDocuments, numberOfPointers, numberOfTokens, numberOfUniqueTerms, termFrequency

Constructor Summary

RequiredTermModifier(boolean r)
Constructs an instance of a TermInFieldModifier given the requirement that the term should, or should not appear in the query.

Method Summary

java.lang.Object	clone() Clone this weighting model
java.lang.String	getInfo() Returns the name of the model.
java.lang.String	getName() Returns the name of the modifier.
int	hashCode() Returns a hash code of this object
int	modifyScores(double[] scores, int[][] pointers) Resets the scores of documents for a particular term, based on the requirement of appearance of the corresponding term.
double	score(double tf, double docLength) This method provides the contract for implementing weighting models.
double	score(double tf, double docLength, double n_t, double F_t, double keyFrequency) This method provides the contract for implementing weighting models.
double	score(Posting p) Returns score

Methods inherited from class org.terrier.matching.models.WeightingModel

getOverflowed, getParameter, prepare, setAverageDocumentLength, setCollectionStatistics, setDocumentFrequency, setEntryStatistics, setKeyFrequency, setNumberOfDocuments, setNumberOfPointers, setNumberOfTokens, setNumberOfUniqueTerms, setParameter, setRequest, setTermFrequency, stirlingPower

Methods inherited from class java.lang.Object

equals, finalize, getClass, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

RequiredTermModifier

public RequiredTermModifier(boolean r)

Constructs an instance of a TermInFieldModifier given the requirement that the term should, or should not appear in the query.

Parameters:

r - boolean indicates whether the term is required to appear in the retrieved documents.

Method Detail

modifyScores

public int modifyScores(double[] scores,
                        int[][] pointers)

Resets the scores of documents for a particular term, based on the requirement of appearance of the corresponding term.

Specified by:

modifyScores in interface TermScoreModifier

Parameters:

scores - double[] the scores of the documents.

pointers - int[][] the pointers read from the inverted file for a particular query term.

Returns:

the number of documents for which the scores were modified.

getName

public java.lang.String getName()

Returns the name of the modifier.

Specified by:

getName in interface TermScoreModifier

Returns:

String the name of the modifier.

hashCode

public int hashCode()

Returns a hash code of this object

Specified by:

hashCode in interface TermScoreModifier

Overrides:

hashCode in class java.lang.Object

clone

public java.lang.Object clone()

Clone this weighting model

Specified by:

clone in interface TermScoreModifier

Overrides:

clone in class WeightingModel

getInfo

public java.lang.String getInfo()

Description copied from class: WeightingModel

Returns the name of the model.

Specified by:

getInfo in interface Model

Specified by:

getInfo in class WeightingModel

Returns:

java.lang.String

score

public double score(Posting p)

Returns score

Overrides:

score in class WeightingModel

Returns:

score

score

public double score(double tf,
                    double docLength)

Description copied from class: WeightingModel

This method provides the contract for implementing weighting models.

Specified by:

score in class WeightingModel

Parameters:

tf - The term frequency in the document

docLength - the document's length

Returns:

the score assigned to a document with the given tf and docLength, and other preset parameters

score

public double score(double tf,
                    double docLength,
                    double n_t,
                    double F_t,
                    double keyFrequency)

Description copied from class: WeightingModel

This method provides the contract for implementing weighting models.

Specified by:

score in class WeightingModel

Parameters:

tf - The term frequency in the document

docLength - the document's length

n_t - The document frequency of the term

F_t - the term frequency in the collection

keyFrequency - the term frequency in the query

Returns:

the score returned by the implemented weighting model.