org.terrier.matching.dsms
Class BooleanFallback

java.lang.Object
  org.terrier.matching.dsms.BooleanFallback

All Implemented Interfaces:

java.lang.Cloneable, DocumentScoreModifier

public class BooleanFallback
extends java.lang.Object
implements DocumentScoreModifier

This class provides a boolean fallback document score modifier for matching. In other words, if there any of the retrieved documents contain all undecorated query terms (ie query terms without any operators), then we remove from the result set documents that do not contain all undecorated query terms. Otherwise, we do nothing.

Author:

Vassilis Plachouras & Craig Macdonald

Field Summary

protected static org.apache.log4j.Logger

logger

Constructor Summary

BooleanFallback()

Method Summary

java.lang.Object	clone() Creates the close of this object
protected java.util.HashSet<java.lang.String>	getMinusTerms(Query q) Builds a hashset containing all terms that are required NOT to be in the query
java.lang.String	getName() Returns the name of the modifier, which is BooleanFallback.
boolean	modifyScores(Index index, MatchingQueryTerms queryTerms, ResultSet resultSet) Applies boolean fallback to the given result set.

Methods inherited from class java.lang.Object

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

Field Detail

logger

protected static final org.apache.log4j.Logger logger

Constructor Detail

BooleanFallback

public BooleanFallback()

Method Detail

getMinusTerms

protected java.util.HashSet<java.lang.String> getMinusTerms(Query q)

Builds a hashset containing all terms that are required NOT to be in the query

Parameters:

q - The original query as was used to generate MatchingQueryTerms

Returns:

See above

modifyScores

public boolean modifyScores(Index index,
                            MatchingQueryTerms queryTerms,
                            ResultSet resultSet)

Applies boolean fallback to the given result set.

Specified by:

modifyScores in interface DocumentScoreModifier

Parameters:

index - The data structures used for retrieval.

queryTerms - the terms of the query.

resultSet - the set of retrieved documents for the query.

Returns:

true if any scores have been altered

getName

public java.lang.String getName()

Returns the name of the modifier, which is BooleanFallback.

Specified by:

getName in interface DocumentScoreModifier

Returns:

the name of the modifier.

clone

public java.lang.Object clone()

Creates the close of this object

Specified by:

clone in interface DocumentScoreModifier

Overrides:

clone in class java.lang.Object