org.apache.jena.reasoner.rulesys.impl

Class ConsumerChoicePointFrame

java.lang.Object

org.apache.jena.reasoner.rulesys.impl.FrameObject

org.apache.jena.reasoner.rulesys.impl.GenericChoiceFrame

org.apache.jena.reasoner.rulesys.impl.GenericTripleMatchFrame

org.apache.jena.reasoner.rulesys.impl.ConsumerChoicePointFrame

All Implemented Interfaces:

LPAgendaEntry, LPInterpreterState

public class ConsumerChoicePointFrame
extends GenericTripleMatchFrame
implements LPAgendaEntry, LPInterpreterState

Frame in the LPInterpreter's control stack used to represent matching to the results of a tabled predicate. Conventionally the system state which finds and tables the goal results is called the generator and states which require those results are called consumers.

This is used in the inner loop of the interpreter and so is a pure data structure not an abstract data type and assumes privileged access to the interpreter state.

Constructor Summary

Constructors

Constructor and Description
ConsumerChoicePointFrame(LPInterpreter interpreter) Constructor.

Method Summary

Modifier and Type	Method and Description
void	close() Close the frame actively.
LPInterpreterContext	getConsumingContext() Return the interpeter context which is reading the results of this consumer.
Generator	getGenerator() Return the generator associated with this entry (might be the entry itself)
void	init(LPInterpreter interpreter) Initialize the choice point state.
boolean	isReady() Return true if this choice point could usefully be restarted.
StateFlag	nextMatch(LPInterpreter interpreter) Find the next result triple and bind the result vars appropriately.
void	preserveState(List<Node> trail) Preserve the state of an interpreter into this frame.
void	pump() Reactivate this choice point to return new results.
void	restoreState(LPInterpreter interp) Restore the state of an interpreter from this frame
void	setFinished() Notify that this consumer choice point has finished consuming all the results of a closed generator.
void	setReady() Called by generator when there are more results available.

Methods inherited from class org.apache.jena.reasoner.rulesys.impl.GenericTripleMatchFrame

bindResult, functorMatch

Methods inherited from class org.apache.jena.reasoner.rulesys.impl.GenericChoiceFrame

setContinuation

Methods inherited from class org.apache.jena.reasoner.rulesys.impl.FrameObject

fastLinkTo, getLink, linkTo

Methods inherited from class java.lang.Object

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

Constructor Detail

ConsumerChoicePointFrame

public ConsumerChoicePointFrame(LPInterpreter interpreter)

Constructor.

Parameters:

interpreter - the parent interpreter whose state is to be preserved here, its arg stack defines the parameters for the target goal

Method Detail

init

public void init(LPInterpreter interpreter)

Initialize the choice point state.

Overrides:

init in class GenericTripleMatchFrame

Parameters:

interpreter - the parent interpreter whose state is to be preserved here, its arg stack defines the parameters for the target goal

preserveState

public void preserveState(List<Node> trail)

Preserve the state of an interpreter into this frame.

restoreState

public void restoreState(LPInterpreter interp)

Restore the state of an interpreter from this frame

nextMatch

public StateFlag nextMatch(LPInterpreter interpreter)

Find the next result triple and bind the result vars appropriately.

Parameters:

interpreter - the calling interpreter whose trail should be used

Returns:

FAIL if there are no more matches and the generator is closed, SUSPEND if there are no more matches but the generator could generate more, SATISFIED if a match has been found.

isReady

public boolean isReady()

Return true if this choice point could usefully be restarted.

Specified by:

isReady in interface LPAgendaEntry

setReady

public void setReady()

Called by generator when there are more results available.

close

public void close()

Description copied from class: FrameObject

Close the frame actively. This frees any internal resources, frees this frame and frees the frame to which this is linked.

Overrides:

close in class FrameObject

setFinished

public void setFinished()

Notify that this consumer choice point has finished consuming all the results of a closed generator.

pump

public void pump()

Reactivate this choice point to return new results.

Specified by:

pump in interface LPAgendaEntry

getGenerator

public Generator getGenerator()

Return the generator associated with this entry (might be the entry itself)

Specified by:

getGenerator in interface LPAgendaEntry

getConsumingContext

public LPInterpreterContext getConsumingContext()

Return the interpeter context which is reading the results of this consumer.