org.terrier.matching.models
Class DPH

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

All Implemented Interfaces:

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

public class DPH
extends WeightingModel

This class implements the DPH hypergeometric weighting model. P stands for Popper's normalization. This is a parameter-free weighting model. Even if the user specifies a parameter value, it will NOT affect the results. It is highly recomended to use the model with query expansion.

References

1. FUB, IASI-CNR and University of Tor Vergata at TREC 2007 Blog Track. G. Amati and E. Ambrosi and M. Bianchi and C. Gaibisso and G. Gambosi. Proceedings of the 16th Text REtrieval Conference (TREC-2007), 2008.
2. Frequentist and Bayesian approach to Information Retrieval. G. Amati. In Proceedings of the 28th European Conference on IR Research (ECIR 2006). LNCS vol 3936, pages 13--24.

Author:

Gianni Amati, Ben He, Vassilis Plachouras

See Also:

Serialized Form

Field Summary

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

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

Constructor Summary

DPH()
A default constructor.

Method Summary

java.lang.String	getInfo() Returns the name of the model.
double	score(double tf, double docLength) Uses DPH to compute a weight for a term in a document.
double	score(double tf, double docLength, double n_t, double F_t, double keyFrequency) Uses DPH to compute a weight for a term in a document.

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

clone, getOverflowed, getParameter, prepare, score, setAverageDocumentLength, setCollectionStatistics, setDocumentFrequency, setEntryStatistics, 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

Constructor Detail

DPH

public DPH()

A default constructor.

Method Detail

getInfo

public final java.lang.String getInfo()

Returns the name of the model.

Specified by:

getInfo in interface Model

Specified by:

getInfo in class WeightingModel

Returns:

the name of the model

score

public final double score(double tf,
                          double docLength)

Uses DPH to compute a weight for a term in a document.

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 final double score(double tf,
                          double docLength,
                          double n_t,
                          double F_t,
                          double keyFrequency)

Uses DPH to compute a weight for a term in a document.

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 assigned by the weighting model DPH.