org.terrier.matching.models
Class ML2

java.lang.Object
  org.terrier.matching.models.WeightingModel
      org.terrier.matching.models.ML2

All Implemented Interfaces:

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

public class ML2
extends WeightingModel

This class implements the ML2 field-based weighting model.

Properties

:

• c.0, c.1, etc. Normalisation parameter for each field.
• p.0, p.1, etc. Prior weight adjustments for each field. In the original paper, all of these were left at the default value of 1.0d.

If you use this model, please cite V. Plachouras and I. Ounis, Multinomial Randomness Models for Retrieval with Document Fields, In Proc. ECIR 2007.

Since:

3.0

Author:

Vassilis Plachouras and Craig Macdonald

See Also:

Serialized Form

Field Summary

protected int	fieldCount
protected int[]	fieldTermFrequencies
protected double[]	fieldWeights
protected double[]	p

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

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

Constructor Summary

ML2(java.lang.String[] parameters)
Constructs an instance of ML2

Method Summary

java.lang.String	getInfo() Returns the name of the model.
void	prepare() prepare
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
void	setCollectionStatistics(CollectionStatistics _cs) Sets collection statistics
void	setEntryStatistics(EntryStatistics _es) Sets entry statistics.

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

clone, getOverflowed, getParameter, setAverageDocumentLength, setDocumentFrequency, setKeyFrequency, setNumberOfDocuments, setNumberOfPointers, setNumberOfTokens, setNumberOfUniqueTerms, setParameter, setRequest, setTermFrequency, stirlingPower

Methods inherited from class java.lang.Object

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

Field Detail

fieldCount

protected int fieldCount

fieldWeights

protected double[] fieldWeights

p

protected double[] p

fieldTermFrequencies

protected int[] fieldTermFrequencies

Constructor Detail

ML2

public ML2(java.lang.String[] parameters)
    throws java.lang.Exception

Constructs an instance of ML2

Parameters:

parameters -

Throws:

java.lang.Exception

Method Detail

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

prepare

public void prepare()

Description copied from class: WeightingModel

prepare

Overrides:

prepare in class WeightingModel

setCollectionStatistics

public void setCollectionStatistics(CollectionStatistics _cs)

Description copied from class: WeightingModel

Sets collection statistics

Overrides:

setCollectionStatistics in class WeightingModel

setEntryStatistics

public void setEntryStatistics(EntryStatistics _es)

Description copied from class: WeightingModel

Sets entry statistics.

Overrides:

setEntryStatistics in class WeightingModel

score

public double score(Posting _p)

Description copied from class: WeightingModel

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.