Package org.terrier.matching

Class BaseMatching

java.lang.Object

org.terrier.matching.BaseMatching

All Implemented Interfaces:

Matching

Direct Known Subclasses:

Full, Full

public abstract class BaseMatching
extends java.lang.Object
implements Matching

Performs the matching of documents with a query, by first assigning scores to documents for each query term and modifying these scores with the appropriate modifiers. Then, a series of document score modifiers are applied if necessary.

Properties

• matching.retrieved_set_size - The maximum number of documents in the final retrieved set. The default value is 1000, however, setting the property to 0 will return all matched documents.
• ignore.low.idf.terms - A property that enables to ignore the terms with a low IDF.
• match.empty.query - whether an empty query should return all documents. Defaults to false.

Since:

3.0

Author:

Vassilis Plachouras, Craig Macdonald, Nicola Tonellotto

Nested Class Summary

Nested Classes

Modifier and Type	Class	Description
protected static class	BaseMatching.MatchingState

Field Summary

Fields

Modifier and Type	Field	Description
static java.lang.String	BASE_MATCHING_TAG
protected CollectionStatistics	collectionStatistics	The collection statistics
protected java.util.List<DocumentScoreModifier>	documentModifiers	Contains the document score modifiers to be applied for a query.
protected static java.lang.String	dsmNamespace	the default namespace for the document score modifiers that are specified in the properties file.
protected static boolean	IGNORE_LOW_IDF_TERMS	A property that enables to ignore the terms with a low IDF.
protected Index	index	The index used for retrieval.
protected PostingIndex<Pointer>	invertedIndex	The inverted file.
protected Lexicon<java.lang.String>	lexicon	The lexicon used.
protected static org.slf4j.Logger	logger	the logger for this class
protected static boolean	MATCH_EMPTY_QUERY	A property that when it is true, it allows matching all documents to an empty query.
static java.lang.String	NONMATCHING_TAG

Constructor Summary

Constructors

Modifier	Constructor	Description
protected	BaseMatching()
	BaseMatching(Index _index)	Constructs an instance of the BaseMatching

Method Summary

Modifier and Type	Method	Description
protected void	finalise(BaseMatching.MatchingState state)
abstract java.lang.String	getInfo()	Return a human readable description of this Matching class
protected BaseMatching.MatchingState	initialise(MatchingQueryTerms queryTerms)
protected void	initialisePostings(BaseMatching.MatchingState state)
protected BaseMatching.MatchingState	initialiseState()
abstract ResultSet	match(java.lang.String queryNumber, MatchingQueryTerms queryTerms)	Get a ResultSet for the given query terms.
void	setCollectionStatistics(CollectionStatistics cs)	Update the collection statistics being used by this matching instance

Methods inherited from class java.lang.Object

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

Field Detail

BASE_MATCHING_TAG

public static final java.lang.String BASE_MATCHING_TAG

See Also:

Constant Field Values

NONMATCHING_TAG

public static final java.lang.String NONMATCHING_TAG

See Also:

Constant Field Values

logger

protected static final org.slf4j.Logger logger

the logger for this class

dsmNamespace

protected static java.lang.String dsmNamespace

the default namespace for the document score modifiers that are specified in the properties file.

IGNORE_LOW_IDF_TERMS

protected static boolean IGNORE_LOW_IDF_TERMS

A property that enables to ignore the terms with a low IDF. Corresponds to property ignore.low.idf.terms. Defaults to true. This can cause some query terms to be omitted in small corpora.

MATCH_EMPTY_QUERY

protected static boolean MATCH_EMPTY_QUERY

A property that when it is true, it allows matching all documents to an empty query. In this case the ordering of documents is random. More specifically, it is the ordering of documents in the document index.

index

protected Index index

The index used for retrieval.

lexicon

protected Lexicon<java.lang.String> lexicon

The lexicon used.

invertedIndex

protected PostingIndex<Pointer> invertedIndex

The inverted file.

collectionStatistics

protected CollectionStatistics collectionStatistics

The collection statistics

documentModifiers

protected java.util.List<DocumentScoreModifier> documentModifiers

Contains the document score modifiers to be applied for a query.

Constructor Detail

BaseMatching

protected BaseMatching()

BaseMatching

public BaseMatching(Index _index)

Constructs an instance of the BaseMatching

Parameters:

_index -

Method Detail

initialiseState

protected BaseMatching.MatchingState initialiseState()

initialisePostings

protected void initialisePostings(BaseMatching.MatchingState state)

initialise

protected BaseMatching.MatchingState initialise(MatchingQueryTerms queryTerms)

finalise

protected void finalise(BaseMatching.MatchingState state)

setCollectionStatistics

public void setCollectionStatistics(CollectionStatistics cs)

Update the collection statistics being used by this matching instance

Specified by:

setCollectionStatistics in interface Matching

Parameters:

cs - CollectionStatistics to use during matching

getInfo

public abstract java.lang.String getInfo()

Return a human readable description of this Matching class

Specified by:

getInfo in interface Matching

match

public abstract ResultSet match(java.lang.String queryNumber,
                                MatchingQueryTerms queryTerms)
                         throws java.io.IOException

Get a ResultSet for the given query terms.

Specified by:

match in interface Matching

Parameters:

queryNumber - - some ID of the query

queryTerms - - query terms to match

Returns:

ResultSet - the matched results

Throws:

java.io.IOException - if a problem occurs during matching