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

Class LigerRefinementOperator

java.lang.Object

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

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

public class LigerRefinementOperator
extends PartialRecallRefinementOperator

Field Summary

Fields

Modifier and Type	Field and Description
protected static org.apache.log4j.Logger	logger

Fields inherited from class org.aksw.limes.core.execution.engine.partialrecallengine.refinement.PartialRecallRefinementOperator

best, buffer, desiredSelectivity, k, maxOpt, root, source, target, thresholds, timeLimit, total

Constructor Summary

Constructors

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

Method Summary

Modifier and Type	Method and Description
void	addSpecifications(List<LinkSpecification> specs) Creates the set of to-be-refined nodes by adding specification that does not already exists in total set and their selectivity is higher or equal to the desired selectivity.
HashMap<LinkSpecification,Plan>	getNewNodes()
List<LinkSpecification>	merge(LinkSpecification parent, List<LinkSpecification> leftChildren, List<LinkSpecification> rightChildren, boolean isLeft) Creates a set of new specification by cloning the input specification, keeping one child specification as is, and substitutes the other child specification with the set of specification retrieved by refining the other child.
void	optimize() Implements the basic idea of LIGER: Link Discovery with Guaranteed Recall.
List<LinkSpecification>	refine(LinkSpecification currentSpec) Implements the refinement operator for guaranteed recall.
LinkSpecification	refineAtomicLinkSpecification(LinkSpecification currentSpec) Refines an atomic link specification by calling the next(threshold) function.

Methods inherited from class org.aksw.limes.core.execution.engine.partialrecallengine.refinement.PartialRecallRefinementOperator

checkSelectivity, getBest, getDesiredSelectivity, getOptimizationTime, getRecall, init, next

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

Constructor Detail

LigerRefinementOperator

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

Method Detail

getNewNodes

public HashMap<LinkSpecification,Plan> getNewNodes()

optimize

public void optimize()

Implements the basic idea of LIGER: Link Discovery with Guaranteed Recall. The algorithm's main loop starts and run until the total optimization time has exceeded maxOpt, the buffer or unrefined specification is empty or the selectivity of the best subsumed LS is equal to the desired selectivity. At the beginning of each iteration, the first element of the buffer queue is popped out and the algorithm checks if it receives a better run time score compared to the best specification's runtime estimation. If the new specifications achieves a better runtime estimation, the algorithm assigns it as the best specification. If the new best specification has achieved the desired selectivity, the algorithm terminates. Then, LIGER calls the function refine(), which implements the refinement operator. A new subsumed specification resulted from the refinement is stored iff it does not already exists in total set and its selectivity is higher or equal to the desired selectivity. Finally, the algorithm performs a hierarchical ordering of the specifications in the buffer queue with respect to runtime estimations.

Specified by:

optimize in class PartialRecallRefinementOperator

addSpecifications

public void addSpecifications(List<LinkSpecification> specs)

Creates the set of to-be-refined nodes by adding specification that does not already exists in total set and their selectivity is higher or equal to the desired selectivity.

Parameters:

specs, - the input set of unchecked specifications

refine

public List<LinkSpecification> refine(LinkSpecification currentSpec)

Implements the refinement operator for guaranteed recall.

Parameters:

currentSpec, - an input specification

Returns:

a list of refined specifications

refineAtomicLinkSpecification

public LinkSpecification refineAtomicLinkSpecification(LinkSpecification currentSpec)

Refines an atomic link specification by calling the next(threshold) function.

Parameters:

currentSpec,an - input specification

Returns:

null if the currentSpec can not be refine anymore, or a refined atomic specification

merge

public List<LinkSpecification> merge(LinkSpecification parent,
                                     List<LinkSpecification> leftChildren,
                                     List<LinkSpecification> rightChildren,
                                     boolean isLeft)

Creates a set of new specification by cloning the input specification, keeping one child specification as is, and substitutes the other child specification with the set of specification retrieved by refining the other child.

Parameters:

parent, - an input specification

leftChildren, - a set of left (refined) children specifications

rightChildren, - a set of right (refined) children specifications

isLeft, - flag that indicates with child, left or right, has been refined previously

Returns:

a set of specifications subsumed by the parent specification