org.terrier.matching.tsms

Class RequiredTermModifier

java.lang.Object

org.terrier.matching.models.WeightingModel

org.terrier.matching.tsms.RequiredTermModifier

All Implemented Interfaces:

Serializable, Cloneable, Model

public class RequiredTermModifier
extends WeightingModel
implements 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, cs, documentFrequency, es, i, keyFrequency, numberOfDocuments, numberOfPointers, numberOfTokens, numberOfUniqueTerms, rq, termFrequency

Constructor Summary

Constructors

Constructor and Description
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

Methods

Modifier and Type	Method and Description
String	getInfo() Returns the name of the model.
String	getName() Returns the name of the class and whether the query term is required.
int	hashCode()
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(Posting p) Returns score

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

clone, getOverflowed, getParameter, prepare, setCollectionStatistics, setEntryStatistics, setKeyFrequency, setParameter, setRequest

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.

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 String getName()

Returns the name of the class and whether the query term is required.

hashCode

public int hashCode()

Overrides:

hashCode in class Object

getInfo

public 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