Package org.terrier.matching.models

Class WeightingModel

java.lang.Object

org.terrier.matching.models.WeightingModel

All Implemented Interfaces:

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

Direct Known Subclasses:

BB2, BM25, CoordinateMatch, DFIC, DFIZ, DFR_BM25, DFRee, DFReeKLIM, DFRWeightingModel, DirichletLM, Dl, DLH, DLH13, DPH, Hiemstra_LM, IFB2, In_expB2, In_expC2, InB2, InL2, Js_KLs, LemurTF_IDF, LGD, MDL2, ML2, MRF, Null, pBiL, PerFieldNormWeightingModel, PL2, RequiredTermModifier, SingleFieldModel, StaticScoreModifierWeightingModel, TermInFieldModifier, Tf, TF_IDF, XSqrA_M

public abstract class WeightingModel
extends java.lang.Object
implements Model, java.io.Serializable, java.lang.Cloneable

This class should be extended by the classes used for weighting terms and documents.

Author:

Gianni Amati, Ben He, Vassilis Plachouras

See Also:

Serialized Form

Field Summary

Fields

Modifier and Type	Field	Description
protected double	averageDocumentLength	The average length of documents in the collection.
protected double	c	The parameter c.
protected CollectionStatistics	cs
protected double	documentFrequency	The document frequency of the term in the collection.
protected EntryStatistics	es
protected Idf	i	The class used for computing the idf values.
protected double	keyFrequency	The term frequency in the query.
protected double	numberOfDocuments	The number of documents in the collection.
protected double	numberOfPointers	Deprecated.
protected double	numberOfPostings	The number of distinct entries in the inverted file.
protected double	numberOfTokens	The number of tokens in the collections.
protected double	numberOfUniqueTerms	Number of unique terms in the collection
protected Request	rq
protected double	termFrequency	The term frequency in the collection.

Constructor Summary

Constructors

Constructor	Description
WeightingModel()	A default constructor that initialises the idf i attribute

Method Summary

Modifier and Type	Method	Description
WeightingModel	clone()	Clone this weighting model
abstract java.lang.String	getInfo()	Returns the name of the model.
static long	getOverflowed(int o)	Returns overflow
double	getParameter()	Returns the parameter as set by setParameter()
void	prepare()	prepare
abstract double	score(double tf, double docLength)	This method provides the contract for implementing weighting models.
double	score(Posting p)	Returns score
void	setCollectionStatistics(CollectionStatistics _cs)	Sets collection statistics
void	setEntryStatistics(EntryStatistics _es)	Sets entry statistics.
void	setKeyFrequency(double keyFreq)	Sets the term's frequency in the query.
void	setParameter(double _c)	Sets the c value
void	setRequest(Request _rq)	Sets request

Methods inherited from class java.lang.Object

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

Field Detail

i

protected Idf i

The class used for computing the idf values.

averageDocumentLength

protected double averageDocumentLength

The average length of documents in the collection.

keyFrequency

protected double keyFrequency

The term frequency in the query.

documentFrequency

protected double documentFrequency

The document frequency of the term in the collection.

termFrequency

protected double termFrequency

The term frequency in the collection.

numberOfDocuments

protected double numberOfDocuments

The number of documents in the collection.

numberOfTokens

protected double numberOfTokens

The number of tokens in the collections.

c

protected double c

The parameter c. This defaults to 1.0, but should be set using in the constructor of each child weighting model to the sensible default for that weighting model.

numberOfUniqueTerms

protected double numberOfUniqueTerms

Number of unique terms in the collection

numberOfPointers

@Deprecated
protected double numberOfPointers

Deprecated.

The number of distinct entries in the inverted file. This figure can be calculated as the sum of all Nt over all terms. Deprecated in favour of numberOfPostings

numberOfPostings

protected double numberOfPostings

The number of distinct entries in the inverted file. This figure can be calculated as the sum of all Nt over all terms

cs

protected CollectionStatistics cs

es

protected EntryStatistics es

rq

protected Request rq

Constructor Detail

WeightingModel

public WeightingModel()

A default constructor that initialises the idf i attribute

Method Detail

clone

public WeightingModel clone()

Clone this weighting model

Overrides:

clone in class java.lang.Object

getInfo

public abstract java.lang.String getInfo()

Returns the name of the model.

Specified by:

getInfo in interface Model

Returns:

java.lang.String

prepare

public void prepare()

prepare

getOverflowed

public static long getOverflowed(int o)

Returns overflow

Parameters:

o -

Returns:

overflow

score

public double score(Posting p)

Returns score

Parameters:

p -

Returns:

score

setCollectionStatistics

public void setCollectionStatistics(CollectionStatistics _cs)

Sets collection statistics

Parameters:

_cs -

setEntryStatistics

public void setEntryStatistics(EntryStatistics _es)

Sets entry statistics.

Parameters:

_es -

setRequest

public void setRequest(Request _rq)

Sets request

Parameters:

_rq -

score

public abstract double score(double tf,
                             double docLength)

This method provides the contract for implementing weighting models.

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

setParameter

public void setParameter(double _c)

Sets the c value

Specified by:

setParameter in interface Model

Parameters:

_c - the term frequency normalisation parameter value.

getParameter

public double getParameter()

Returns the parameter as set by setParameter()

Specified by:

getParameter in interface Model

setKeyFrequency

public void setKeyFrequency(double keyFreq)

Sets the term's frequency in the query.

Parameters:

keyFreq - the term's frequency in the query.