org.terrier.matching

Class BaseMatching

java.lang.Object

org.terrier.matching.BaseMatching

All Implemented Interfaces:

Matching

Direct Known Subclasses:

Full, Full, FullNoPLM, FullNoPLM

public abstract class BaseMatching
extends 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

Field Summary

Fields

Modifier and Type	Field and Description
protected CollectionStatistics	collectionStatistics The collection statistics
protected List<DocumentScoreModifier>	documentModifiers Contains the document score modifiers to be applied for a query.
protected static 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<String>	lexicon The lexicon used.
protected static org.apache.log4j.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.
protected int	numberOfRetrievedDocuments The number of retrieved documents for a query.
protected List<Map.Entry<String,LexiconEntry>>	queryTermsToMatchList
protected ResultSet	resultSet The result set.
protected static int	RETRIEVED_SET_SIZE The maximum number of documents in the final retrieved set.
protected long	totalTime
protected WeightingModel[][]	wm

Constructor Summary

Constructors

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

Method Summary

Methods

Modifier and Type	Method and Description
protected void	finalise(MatchingQueryTerms queryTerms)
abstract String	getInfo() Return a human readable description of this Matching class
long	getTotalTime() get the total time
protected void	initialise(MatchingQueryTerms queryTerms)
protected void	initialisePostings(MatchingQueryTerms queryTerms)
abstract ResultSet	match(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
void	updateEndTime(long t) Update the end time.
void	updateStartTime(long t) Update the start time

Methods inherited from class java.lang.Object

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

Field Detail

totalTime

protected long totalTime

logger

protected static final org.apache.log4j.Logger logger

the logger for this class

dsmNamespace

protected static String dsmNamespace

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

RETRIEVED_SET_SIZE

protected static int RETRIEVED_SET_SIZE

The maximum number of documents in the final retrieved set. It corresponds to the property matching.retrieved_set_size. The default value is 1000, however, setting the property to 0 will return all matched documents.

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.

numberOfRetrievedDocuments

protected int numberOfRetrievedDocuments

The number of retrieved documents for a query.

index

protected Index index

The index used for retrieval.

lexicon

protected Lexicon<String> lexicon

The lexicon used.

invertedIndex

protected PostingIndex<Pointer> invertedIndex

The inverted file.

collectionStatistics

protected CollectionStatistics collectionStatistics

The collection statistics

resultSet

protected ResultSet resultSet

The result set.

documentModifiers

protected List<DocumentScoreModifier> documentModifiers

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

wm

protected WeightingModel[][] wm

queryTermsToMatchList

protected List<Map.Entry<String,LexiconEntry>> queryTermsToMatchList

Constructor Detail

BaseMatching

protected BaseMatching()

BaseMatching

public BaseMatching(Index _index)

Constructs an instance of the BaseMatching

Parameters:

_index -

Method Detail

updateStartTime

public void updateStartTime(long t)

Update the start time

Parameters:

t -

updateEndTime

public void updateEndTime(long t)

Update the end time.

Parameters:

t -

getTotalTime

public long getTotalTime()

get the total time

Returns:

long

initialisePostings

protected void initialisePostings(MatchingQueryTerms queryTerms)

initialise

protected void initialise(MatchingQueryTerms queryTerms)

finalise

protected void finalise(MatchingQueryTerms queryTerms)

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 String getInfo()

Return a human readable description of this Matching class

Specified by:

getInfo in interface Matching

match

public abstract ResultSet match(String queryNumber,
              MatchingQueryTerms queryTerms)
                         throws 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:

IOException - if a problem occurs during matching