Js_KLs (Terrier Information Retrieval Platform 5.5 API)

java.lang.Object
- org.terrier.matching.models.WeightingModel
- - org.terrier.matching.models.Js_KLs

All Implemented Interfaces:

java.io.Serializable, java.lang.Cloneable, Model
```
public class Js_KLs
extends WeightingModel
```
This class implements the Js_KLs weighting model, which is the product of two measures: the Jefrreys' divergence with the Kullback Leibler's divergence. The two measures are obtained by the addition of one query token. Then Jefrreys' divergence and the information growth in the document by Kullback Leibler's divergence are computed. The model computes the product of these two information measures as amount of information carried by a single query token. Js_KLs is an unsupervised model (parameter free model) of IR.
Js_KLs has a high performance but it can be used with verbose queries. In particular, it has statistically or moderately significant better MAP performance than most of the supervised models with long queries on the terabyte collection (GOV2) with the exception of PL2. MAP for long topics, and comparative p values (two-tailed paired t-test) compared to supervised models (with optimal MAP parameter values) are as follows:

Queries MAP of JS_KLs LGD Dirichlet_LM PL2 BM25 In_expB2

long 0.3178 (>) p=1.7E-17 (>) p=0.0544 (<) p=0.3155 (>) p=0.7866 (>) p=5151

References
1. 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.
Since:

3.5

Author:

Gianni Amati

See Also:

Serialized Form

Field Summary
- Fields inherited from class org.terrier.matching.models.WeightingModel
  averageDocumentLength, c, cs, documentFrequency, es, i, keyFrequency, numberOfDocuments, numberOfPointers, numberOfPostings, numberOfTokens, numberOfUniqueTerms, rq, termFrequency

Constructor Summary

Constructors
Constructor Description

Js_KLs()
A default constructor to make this model.

Method Summary

All Methods Instance Methods Concrete Methods
Modifier and Type	Method	Description
`java.lang.String`	`getInfo()`	Returns the name of the model, in this case "Js_KLs"
`double`	`score(double tf, double docLength)`	Uses Js_KLs to compute a weight for a term in a document.

Methods inherited from class org.terrier.matching.models.WeightingModel
clone, getOverflowed, getParameter, prepare, score, setCollectionStatistics, setEntryStatistics, setKeyFrequency, setParameter, setRequest

Methods inherited from class java.lang.Object
equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

- Constructor Detail
  - Js_KLs
```
public Js_KLs()
```
    A default constructor to make this model.
- Method Detail
  - getInfo
```
public final java.lang.String getInfo()
```
    Returns the name of the model, in this case "Js_KLs"
    
    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 Js_KLs to compute a weight for a term in a document.
    
    Specified by:
    
    score in class WeightingModel
    
    Parameters:
    
    tf - The term frequency of the term 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