org.terrier.matching.models

Class WeightingModel

java.lang.Object

org.terrier.matching.models.WeightingModel

All Implemented Interfaces:

Serializable, Cloneable, Model

Direct Known Subclasses:

BB2, BM25, 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, PerFieldNormWeightingModel, PL2, RequiredTermModifier, SingleFieldModel, StaticScoreModifierWeightingModel, TermInFieldModifier, Tf, TF_IDF, XSqrA_M

public abstract class WeightingModel
extends Object
implements Model, Serializable, 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 and 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 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 and Description
WeightingModel() A default constructor that initialises the idf i attribute

Method Summary

Methods

Modifier and Type	Method and Description
WeightingModel	clone() Clone this weighting model
abstract 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.
abstract double	score(double tf, double docLength, double n_t, double F_t, double _keyFrequency) Deprecated.
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

protected double numberOfPointers

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 Object

getInfo

public abstract 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

score

@Deprecated
public abstract double score(double tf,
                      double docLength,
                      double n_t,
                      double F_t,
                      double _keyFrequency)

Deprecated.

This method provides the contract for implementing weighting models. As of Terrier 3.6, the 5-parameter score method is being deprecated since is is not used. The two parameter score method should be used instead. Tagged for removal in a later version.

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.

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.