jess
Class Defrule

java.lang.Object
  jess.Node
      jess.HasLHS
          jess.Defrule

All Implemented Interfaces:

jess.MatchInfoSource, Modular, Named, jess.NodeSink, java.io.Serializable, Visitable

public class Defrule

extends HasLHS

implements java.io.Serializable, jess.MatchInfoSource

A Defrule is a specific action meant to be taken when certain conditions are met in working memory. Although you can construct Defrules from the Java API, they are almost always parsed from "defrule" constructs in the Jess language. Building a Defrule from Java is very complicated.

(C) 2005 Sandia National Laboratories

See Also:

Serialized Form

Field Summary

Fields inherited from class jess.Node

LEFT, RIGHT

Constructor Summary

Defrule(java.lang.String name, java.lang.String docstring, Rete engine)

Method Summary

java.lang.Object	accept(Visitor jv) Defrule participates in the Visitor pattern.
void	addAction(Funcall fc) Add an action to this defrule
void	addCE(jess.ConditionalElementX ce, Rete engine) Add a conditional element (a pattern or group of patterns) to this rule.
void	callNodeLeft(int tag, Token token, Context context) An implementation detail, public only because Jave requires methods that implement an interface to be public.
int	evalSalience(Rete engine) Evaluate the salience of this rule.
Funcall	getAction(int idx) Fetch the idx-th RHS action of this rule.
boolean	getAutoFocus() Indicate whether this rule will automatically focus its module when it is activated.
java.lang.String	getConstructType() Return the type of this construct
int	getNActions() Fetch the number of actions on this rule's RHS
int	getSalience() Fetch the current salience value for this rule.
Value	getSalienceValue() Fetch the raw salience for this rule as a jess.Value.
boolean	hasNonDefaultSalience() Indicate whether this rule's salience is different from the default value.
boolean	isNoLoop() Indicate whether this rule can activate itself through actions it takes on its RHS.
boolean	isRelevantChange(int factIndex, Token token, Context context) Implementation detail.
void	setAutoFocus(boolean autoFocus) Tell this rule whether to automatically focus the module it appears in when the rule is activated.
void	setNoLoop(boolean b) Specify whether this rule can activate itself through actions it takes on its RHS.
void	setSalience(Value v, Rete engine) Set the salience of this rule.
java.lang.String	toString() Returns a brief description of this rule

Methods inherited from class jess.HasLHS

addNode, getConditionalElements, getDisplayName, getDocstring, getGroupSize, getModule, getName, getNext, getNodeCount, getNodeIndexHash, getNodes, getPatternCount, listNodes, setLHS, setNodeIndexHash

Methods inherited from class jess.Node

addJessListener, getSuccessors, removeJessListener

Methods inherited from class java.lang.Object

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

Constructor Detail

Defrule

public Defrule(java.lang.String name,
               java.lang.String docstring,
               Rete engine)
        throws JessException

Method Detail

getSalience

public final int getSalience()

Fetch the current salience value for this rule. This method won't re-evaluate the salienc; the last value previously computed will be returned.

Returns:

the salience of this defrule

getSalienceValue

public Value getSalienceValue()

Fetch the raw salience for this rule as a jess.Value. For rules with dynamic salience, the Value returned will be a jess.FuncallValue.

Returns:

the salience of this defrule

setSalience

public void setSalience(Value v,
                        Rete engine)
                 throws JessException

Set the salience of this rule. The value van be a fixed integer, or it can be a function call. The default salience is 0.

Parameters:

v - the salience expression

engine - a Rete object to provide an execution context

Throws:

JessException - if anything goes wrong

evalSalience

public int evalSalience(Rete engine)
                 throws JessException

Evaluate the salience of this rule. If the salience was set to a Funcall value during parsing, then this function may return different values over time. If the salience is constant, this is equivalent to getSalience. The computed value will be the next value returned by getSalience().

Parameters:

engine - The Rete engine the rule belongs to

Returns:

The evaluated salience

Throws:

JessException - If something goes wrong

hasNonDefaultSalience

public boolean hasNonDefaultSalience()

Indicate whether this rule's salience is different from the default value.

Returns:

true if this rule's salience is not the default.

getAutoFocus

public boolean getAutoFocus()

Indicate whether this rule will automatically focus its module when it is activated.

Returns:

the value of this property

setAutoFocus

public void setAutoFocus(boolean autoFocus)

Tell this rule whether to automatically focus the module it appears in when the rule is activated. The default value is false.

Parameters:

autoFocus - the desired value of this property.

addCE

public void addCE(jess.ConditionalElementX ce,
                  Rete engine)
           throws JessException

Add a conditional element (a pattern or group of patterns) to this rule. Normally this will only be called by the Jess parser or the XML parser, but it is theoretically possible for users to build their own rules this way.

Overrides:

addCE in class HasLHS

Parameters:

ce - the conditional element to add

engine - the rule engine that provides the execution context

Throws:

JessException - if anything goes wrong

callNodeLeft

public void callNodeLeft(int tag,
                         Token token,
                         Context context)
                  throws JessException

An implementation detail, public only because Jave requires methods that implement an interface to be public.

Throws:

JessException

getNActions

public int getNActions()

Fetch the number of actions on this rule's RHS

Returns:

The number of actions

getAction

public Funcall getAction(int idx)

Fetch the idx-th RHS action of this rule.

Parameters:

idx - The zero-based index of the action to fetch

Returns:

the action as a function call

addAction

public void addAction(Funcall fc)

Add an action to this defrule

Parameters:

fc - the action as a function call

accept

public java.lang.Object accept(Visitor jv)

Defrule participates in the Visitor pattern. Will call accept(this) on the Visitor.

Specified by:

accept in interface Visitable

Specified by:

accept in class HasLHS

Parameters:

jv - a Visitor

Returns:

whatever jv.accept(this) returns

toString

public java.lang.String toString()

Returns a brief description of this rule

Returns:

the String "Defrule rule-name"

setNoLoop

public void setNoLoop(boolean b)

Specify whether this rule can activate itself through actions it takes on its RHS. If this property is set to true, then modifying a fact on the RHS of this rule can't reactivate the same rule, even if that fact is matched by this rule. The default value is false.

Parameters:

b - the desired value of the property.

isNoLoop

public boolean isNoLoop()

Indicate whether this rule can activate itself through actions it takes on its RHS. If this property is true, then modifying a fact on the RHS of this rule can't reactivate the same rule, even if that fact is matched by this rule.

Returns:

the current value of the property.

getConstructType

public final java.lang.String getConstructType()

Return the type of this construct

Specified by:

getConstructType in interface Named

Returns:

the String "defrule"

isRelevantChange

public boolean isRelevantChange(int factIndex,
                                Token token,
                                Context context)

Implementation detail. Public only because Java requires methods that implement an interface to be public.

Specified by:

isRelevantChange in interface jess.MatchInfoSource