org.terrier.matching.models

Class MDL2

java.lang.Object

org.terrier.matching.models.WeightingModel

org.terrier.matching.models.MDL2

All Implemented Interfaces:

Serializable, Cloneable, Model

public class MDL2
extends WeightingModel

This class implements the MDL2 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

Fields

Modifier and Type	Field and Description
protected int	fieldCount
protected int[]	fieldTermFrequencies
protected double[]	fieldWeights
protected double[]	p

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
MDL2()
MDL2(String[] parameters) Constructs an instance of MDL2.

Method Summary

Methods

Modifier and Type	Method and Description
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) Deprecated.
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, setKeyFrequency, setParameter, setRequest

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

MDL2

public MDL2(String[] parameters)
     throws Exception

Constructs an instance of MDL2.

Parameters:

parameters -

Throws:

Exception

MDL2

public MDL2()

Method Detail

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

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)

Sets entry statistics.

Overrides:

setEntryStatistics in class WeightingModel

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

@Deprecated
public 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 it is not used. The two parameter score method should be used instead. Tagged for removal in a later version.

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.