com.hp.hpl.jena.reasoner.rulesys.builtins
Class Drop

java.lang.Object
  com.hp.hpl.jena.reasoner.rulesys.builtins.BaseBuiltin
      com.hp.hpl.jena.reasoner.rulesys.builtins.Drop

All Implemented Interfaces:

Builtin

public class Drop
extends BaseBuiltin

A variant of the "remove" builtin that will delete matched triples from the graph but will not trigger further rule processing for the removed triples. This makes it seriously non-monotonic but useful for rewrite rules.

Version:

$Revision: 1.6 $

Author:

Dave Reynolds

Field Summary

Fields inherited from class com.hp.hpl.jena.reasoner.rulesys.builtins.BaseBuiltin

BASE_URI

Constructor Summary

Drop()

Method Summary

java.lang.String	getName() Return a name for this builtin, normally this will be the name of the functor that will be used to invoke it.
void	headAction(Node[] args, int length, RuleContext context) This method is invoked when the builtin is called in a rule head.
boolean	isMonotonic() Returns false if this builtin is non-monotonic.

Methods inherited from class com.hp.hpl.jena.reasoner.rulesys.builtins.BaseBuiltin

bodyCall, checkArgs, getArg, getArgLength, getURI, isSafe

Methods inherited from class java.lang.Object

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

Constructor Detail

Drop

public Drop()

Method Detail

getName

public java.lang.String getName()

Return a name for this builtin, normally this will be the name of the functor that will be used to invoke it.

headAction

public void headAction(Node[] args,
                       int length,
                       RuleContext context)

This method is invoked when the builtin is called in a rule head. Such a use is only valid in a forward rule.

Specified by:

headAction in interface Builtin

Overrides:

headAction in class BaseBuiltin

Parameters:

args - the array of argument values for the builtin, this is an array of Nodes.

length - the length of the argument list, may be less than the length of the args array for some rule engines

context - an execution context giving access to other relevant data

isMonotonic

public boolean isMonotonic()

Returns false if this builtin is non-monotonic. This includes non-monotonic checks like noValue and non-monotonic actions like remove/drop. A non-monotonic call in a head is assumed to be an action and makes the overall rule and ruleset non-monotonic. Most JenaRules are monotonic deductive closure rules in which this should be false.

Specified by:

isMonotonic in interface Builtin

Overrides:

isMonotonic in class BaseBuiltin