Package org.terrier.matching.dsms

Class DFRDependenceScoreModifier

java.lang.Object

org.terrier.matching.dsms.DependenceScoreModifier

org.terrier.matching.dsms.DFRDependenceScoreModifier

All Implemented Interfaces:

java.lang.Cloneable, DocumentScoreModifier

public class DFRDependenceScoreModifier
extends DependenceScoreModifier

Implements the pBiL and pBil2 DFR-based dependence models. For more information, see Incorporating Term Dependency in the DFR Framework. Jie Peng, Craig Macdonald, Ben He, Vassilis Plachouras, Iadh Ounis. In Proceedings of SIGIR 2007. July 2007. Amsterdam, the Netherlands. 2007.

Properties

• See properties for DependenceScoreModifier
• proximity.norm2 - should Normalisation2 be applied?, defaults to true
• proximity.norm2.c - c value for Normalisation2, defaults to 1.0

Author:

Vassilis Plachouras, Jie Peng, Craig Macdonald

Field Summary

Fields

Modifier and Type	Field	Description
protected static GammaFunction	gf
protected double	ngramC
protected boolean	norm2	whether to apply Normalisation 2
protected static double	REC_LOG_2

Fields inherited from class org.terrier.matching.dsms.DependenceScoreModifier

avgDocLen, dependency, logger, ngramLength, numTokens, phraseQTWfnid, phraseTerms, w_o, w_t, w_u

Constructor Summary

Constructors

Constructor	Description
DFRDependenceScoreModifier()	Constructs an instance of DFRDependenceScoreModifier.
DFRDependenceScoreModifier(java.lang.String[] pTerms)	Constructs an instance of DFRDependenceScoreModifier.
DFRDependenceScoreModifier(java.lang.String[] pTerms, boolean r)	Constructs an instance of DFRDependenceScoreModifier.

Method Summary

Modifier and Type	Method	Description
boolean	modifyScores(Index index, MatchingQueryTerms terms, ResultSet set)	Modifies the scores of documents, in which there exist, or there does not exist a given phrase.
protected double	scoreFDSD(int _matchingNGrams, int docLength)

Methods inherited from class org.terrier.matching.dsms.DependenceScoreModifier

calculateDependence, clone, countTrue, determineGlobalStatistics, doDependency, getName, NOR, openPostingLists, score, scoreFDSD, setCollectionStatistics

Methods inherited from class java.lang.Object

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

Field Detail

REC_LOG_2

protected static final double REC_LOG_2

gf

protected static final GammaFunction gf

norm2

protected boolean norm2

whether to apply Normalisation 2

ngramC

protected double ngramC

Constructor Detail

DFRDependenceScoreModifier

public DFRDependenceScoreModifier()

Constructs an instance of DFRDependenceScoreModifier.

DFRDependenceScoreModifier

public DFRDependenceScoreModifier(java.lang.String[] pTerms)

Constructs an instance of DFRDependenceScoreModifier.

Parameters:

pTerms -

DFRDependenceScoreModifier

public DFRDependenceScoreModifier(java.lang.String[] pTerms,
                                  boolean r)

Constructs an instance of DFRDependenceScoreModifier.

Parameters:

pTerms -

r -

Method Detail

modifyScores

public boolean modifyScores(Index index,
                            MatchingQueryTerms terms,
                            ResultSet set)

Description copied from class: DependenceScoreModifier

Modifies the scores of documents, in which there exist, or there does not exist a given phrase.

Specified by:

modifyScores in interface DocumentScoreModifier

Overrides:

modifyScores in class DependenceScoreModifier

Parameters:

index - Index the data structures to use.

terms - MatchingQueryTerms the terms to be matched for the query. This does not correspond to the phrase terms necessarily, but to all the terms of the query.

set - ResultSet the result set for the query.

Returns:

true if any scores have been altered

scoreFDSD

protected double scoreFDSD(int _matchingNGrams,
                           int docLength)

Specified by:

scoreFDSD in class DependenceScoreModifier