uk.ac.gla.terrier.querying
Class QueryExpansion

java.lang.Object
  uk.ac.gla.terrier.querying.QueryExpansion

All Implemented Interfaces:

PostProcess

public class QueryExpansion
extends java.lang.Object
implements PostProcess

Implements automatic query expansion as PostFilter that is applied to the resultset after 1st-time matching. Controls

• qemodel : The query expansion model used for Query Expansion. Defauls to Bo1.

Properties

• expansion.terms : The maximum number of most weighted terms in the pseudo relevance set to be added to the original query. The system performs a conservative query expansion if this property is set to 0. A conservation query expansion only reweighs the original query terms without adding new terms to the query.
• expansion.documents : The number of top documents from the 1st pass retrieval to use for QE. The query is expanded from this set of docuemnts, also known as the pseudo relevance set.

Version:

$Revision: 1.27 $

Author:

Gianni Amatti, Ben He, Vassilis Plachouras, Craig Macdonald

Field Summary

static java.lang.String

NAMESPACE_QEMODEL The default namespace of query expansion model classes.

Constructor Summary

QueryExpansion()
The default constructor of QueryExpansion.

Method Summary

void	expandQuery(MatchingQueryTerms query, ResultSet resultSet) This method implements the functionality of expanding a query.
java.lang.String	getInfo() Returns the name of the used query expansion model.
QueryExpansionModel	getQueryExpansionModel(java.lang.String Name) Obtain the query expansion model for QE to use.
void	process(Manager manager, SearchRequest q) Runs the actual query expansion
void	setQueryExpansionModel(QueryExpansionModel QEModel) Set the used query expansion model.

Methods inherited from class java.lang.Object

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

Field Detail

NAMESPACE_QEMODEL

public static final java.lang.String NAMESPACE_QEMODEL

The default namespace of query expansion model classes. The query expansion model names are prefixed with this namespace, if they are not fully qualified.

See Also:

Constant Field Values

Constructor Detail

QueryExpansion

public QueryExpansion()

The default constructor of QueryExpansion.

Method Detail

setQueryExpansionModel

public void setQueryExpansionModel(QueryExpansionModel QEModel)

Set the used query expansion model.

Parameters:

QEModel - QueryExpansionModel The query expansion model to be used.

expandQuery

public void expandQuery(MatchingQueryTerms query,
                        ResultSet resultSet)

This method implements the functionality of expanding a query.

Parameters:

query - MatchingQueryTerms the query terms of the original query.

resultSet - CollectionResultSet the set of retrieved documents from the first pass retrieval.

process

public void process(Manager manager,
                    SearchRequest q)

Runs the actual query expansion

Specified by:

process in interface PostProcess

Parameters:

manager - The manager instance handling this search session.

q - the current query being processed

See Also:

PostProcess.process(uk.ac.gla.terrier.querying.Manager,uk.ac.gla.terrier.querying.SearchRequest)

getQueryExpansionModel

public QueryExpansionModel getQueryExpansionModel(java.lang.String Name)

Obtain the query expansion model for QE to use. This will be cached in a hashtable for the lifetime of the application. If Name does not contain ".", then NAMESPACE_QEMODEL will be prefixed to it before loading.

Parameters:

Name - the naem of the query expansion model to load.

getInfo

public java.lang.String getInfo()

Returns the name of the used query expansion model.

Specified by:

getInfo in interface PostProcess

Returns:

String the name of the used query expansion model.