org.aksw.limes.core.execution.engine.partialrecallengine.refinement

Class PartialRecallRefinementOperator

java.lang.Object

org.aksw.limes.core.execution.engine.partialrecallengine.refinement.PartialRecallRefinementOperator

Direct Known Subclasses:

LigerRefinementOperator

public abstract class PartialRecallRefinementOperator
extends Object

Field Summary

Fields

Modifier and Type	Field and Description
protected PartialRecallRefinementNode	best
protected LinkedList<PartialRecallRefinementNode>	buffer
protected double	desiredSelectivity
protected double	k
protected static org.apache.log4j.Logger	logger
protected long	maxOpt
protected PartialRecallRefinementNode	root
protected ACache	source
protected ACache	target
protected List<Double>	thresholds
protected long	timeLimit
protected HashSet<String>	total

Constructor Summary

Constructors

Constructor and Description
PartialRecallRefinementOperator(ACache s, ACache t, double recall, long optTime, LinkSpecification spec)

Method Summary

Modifier and Type	Method and Description
protected int	checkSelectivity(double selectivity) Compares an input selectivity value with the desired selectivity.
PartialRecallRefinementNode	getBest()
double	getDesiredSelectivity()
long	getOptimizationTime()
double	getRecall()
protected void	init(LinkSpecification spec) Initializes refinement procedure.
protected double	next(double currentThreshold) Implements the next function.
abstract void	optimize()

Methods inherited from class java.lang.Object

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

Field Detail

logger

protected static final org.apache.log4j.Logger logger

root

protected PartialRecallRefinementNode root

best

protected PartialRecallRefinementNode best

desiredSelectivity

protected double desiredSelectivity

source

protected ACache source

target

protected ACache target

timeLimit

protected long timeLimit

k

protected double k

maxOpt

protected long maxOpt

thresholds

protected List<Double> thresholds

buffer

protected LinkedList<PartialRecallRefinementNode> buffer

total

protected HashSet<String> total

Constructor Detail

PartialRecallRefinementOperator

public PartialRecallRefinementOperator(ACache s,
                                       ACache t,
                                       double recall,
                                       long optTime,
                                       LinkSpecification spec)

Method Detail

getRecall

public double getRecall()

getOptimizationTime

public long getOptimizationTime()

getBest

public PartialRecallRefinementNode getBest()

getDesiredSelectivity

public double getDesiredSelectivity()

optimize

public abstract void optimize()

checkSelectivity

protected int checkSelectivity(double selectivity)

Compares an input selectivity value with the desired selectivity. If the input selectivity is equal to the desired selectivity, the function returns 0. If the input selectivity is lower than the desired selectivity, it returns a value lower than 0. If the input selectivity is larger than the desired selectivity, it returns a value larger than 0.

Parameters:

selectivity -

Returns:

next

protected double next(double currentThreshold)

Implements the next function. For an input threshold, it returns the first larger threshold from a set of predefined thresholds. The returned value can be at most 1.0. If the input threshold is already 1.0, it returns a negative number that indicates that the link specification, to which the input threshold belongs to, can not be refined any further.

Parameters:

currentThreshold, - the input threshold

Returns:

a value that is the first larger value than currentThreshold from a set of predefined values, or a negative number if the currentThreshold is already 1.0

init

protected void init(LinkSpecification spec)

Initializes refinement procedure. It computes the canonical plan of the input LS and based on its estimated selectivity, it computes the minimum expected selectivity that a rapidly executable link specification subsumed by L must achieve, based on the minimal expected recall requirement set by the user. It also adds the input link specification to the buffer and total structure. The buffer structure serves as a queue and includes link specifications obtained by refining the initial specifications, but have not yet been refined. All specifications, that were generated through the refinement procedure as well as the input specification, are stored in the total set. By keeping track of these specifications, LIGER avoids refining a specification more than once and address the redundancy of the refinement operator. This function also initializes the best specification with the initial specification. The best specification is updated via the main LIGER function, optimize(). The best specification is the subsumed specification with the lowest runtime estimation, that abides to the minimal expected recall requirement.

Parameters:

spec, - the input link specification