com.ibm.able.rules
Class AblePatternMatchEngine

java.lang.Object
  com.ibm.able.rules.AbleInferenceEngine
      com.ibm.able.rules.AblePatternMatchEngine

All Implemented Interfaces:

java.io.Serializable

public class AblePatternMatchEngine

extends AbleInferenceEngine

implements java.io.Serializable

This class provides the inferencing algorithm for processing a set of pattern match rules in a ruleblock using data-driven or forward chaining. This engine implements the Rete' network algorithm which caches partial matches. It will produce identical results to the AblePatternMatchLiteEngine but with be more efficient when used for problems with large numbers of rules and/or working memory objects. When objects are added to working memory, only those test conditions which must be evaluated are processed.

The AblePatternMatchEngine processes AbleAssertionRules and AblePatternMatchRules and ignores all others.

The major processing method is infer() which is called by the AbleRuleSet bean as part of the normal bean process() method.

Instances of this class are not directly constructed by the user but are dynamically created by the AbleRuleBlock init() method.

See Also:

AbleRuleSet, AbleRuleBlock, AblePatternMatchRule, AblePatternMatchLiteEngine, Serialized Form

Nested Class Summary

protected static class

AblePatternMatchEngine.patternMatchRuleComparator

Field Summary

protected java.util.TreeSet	conflictSet
protected java.util.Hashtable	firedRuleBindingPairs
protected AblePatternMatchNetwork	myPatternMatchNet

Fields inherited from class com.ibm.able.rules.AbleInferenceEngine

myDebugLevel, myRuleBlock, myRuleSet, myRulesFiredCount, myTracer, myWorkingMemory

Constructor Summary

AblePatternMatchEngine(AbleRuleSet theRuleSet, AbleLogger theTracer, AbleRuleBlock theRuleBlock)
Create a new inference engine.

Method Summary

boolean	addRuleToConflictSet(AblePatternMatchRule theRule) Inserts the Rule into the conflict set based on priority and specificity.
AbleWorkingMemory	allocateWorkingMemory() Retrieve the workingMemory object (may be null).
protected void	evalPatternMatchRule(AblePatternMatchRule theRule) Evaluate a pattern-match (when-do) rule.
java.lang.Object	getControlParameter(java.lang.String theControlParameter) Returns the specified control parameter on the associated inference engine.
void	infer(AbleRuleBlock theRuleBlock) Fire the rules in the ruleset using pattern match rules and forward chaining inferencing.
boolean	isRuleBlockValid(AbleRuleBlock theRuleBlock) Make sure the current ruleblock is "executable" by this inference engine.
protected void	logConflictSet(java.util.SortedSet conflictSet) Write the contents of the conflict set (triggered rules) to the Inference trace log
protected void	logWorkingMemory() Write the contents of working memory out to the Inference trace log.
boolean	removeRuleFromConflictSet(AblePatternMatchRule theRule) Inserts the Rule into the conflict set based on priority and specificity.
void	setControlParameter(java.lang.String theControlParameter, java.lang.Object theValue) Set the specified control parameter on the associated inference engine.

Methods inherited from class com.ibm.able.rules.AbleInferenceEngine

askUser, conditionalRulesValid, evalAntecedentClause, evalAntecedentExpression, evalAssertionClause, evalAssertionRule, evalConditionalRule, evalConsequentClause, evalDoUntilRule, evalDoWhileRule, evalForLoopRule, evalIfThenElseRule, evalSwitchRule, evaluateDoActions, evalWhileDoRule, fireEngineBreakpoint, firePropertyChange, getRuleSet, getRulesFiredCount, getWorkingMemory, init, processAssertions, processConsequent, processConsequent, processConsequentClauses, processRuleBlock, reset, resetRuleSet, setControlParameters, setDebugLevel, setInferenceContext, setInferenceContext, setInferenceContext, setRuleSet, setWorkingMemory, startDebugConsole, stopDebugConsole, toString

Methods inherited from class java.lang.Object

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

Field Detail

myPatternMatchNet

protected AblePatternMatchNetwork myPatternMatchNet

firedRuleBindingPairs

protected transient java.util.Hashtable firedRuleBindingPairs

conflictSet

protected transient java.util.TreeSet conflictSet

Constructor Detail

AblePatternMatchEngine

public AblePatternMatchEngine(AbleRuleSet theRuleSet,
                              AbleLogger theTracer,
                              AbleRuleBlock theRuleBlock)

Create a new inference engine.

Parameters:

theRuleSet - A ruleset whose context is used for inferencing by this inference engine.

theTracer - A tracer object to which this inference engine can log information. This may be null, in which case no information is logged.

theRuleBlock - A ruleblock whose rules are to be used for inferencing by this inference engine.

Method Detail

isRuleBlockValid

public boolean isRuleBlockValid(AbleRuleBlock theRuleBlock)

Make sure the current ruleblock is "executable" by this inference engine. Only assertion rules and pattern match rules are processed.

The ruleblock is invalid if any of the following are present in the ruleblock:

Conditional rule

If-then-else rule

Predicate rule

Iteration rule

All reasons for validation failures are appended to the AbleRuleSet's myIsExReason variable. If validation fails, the inference engine must call myRuleSet.addIsExReason(java.lang.String) to append the reason.

Specified by:

isRuleBlockValid in class AbleInferenceEngine

Returns:

true, if the ruleset is OK; false, if the ruleset is not executable.

infer

public void infer(AbleRuleBlock theRuleBlock)
           throws AbleDataException

Fire the rules in the ruleset using pattern match rules and forward chaining inferencing.

The order of processing is as follows:

1. Sequentially process all assertion rules in the ruleblock.
2. Evaluate all pattern match rules using forward chaining and a working memory.

Specified by:

infer in class AbleInferenceEngine

Parameters:

theRuleBlock - The ruleblock to be processed.

Throws:

AbleDataException - When any error occurs.

evalPatternMatchRule

protected void evalPatternMatchRule(AblePatternMatchRule theRule)
                             throws AbleDataException

Evaluate a pattern-match (when-do) rule.

Procesing is as follows:

• Evaluate the pattern match clause.
• If the match returns any bindings the rule is triggered and could be selected to fire.

Overrides:

evalPatternMatchRule in class AbleInferenceEngine

Throws:

AbleDataException - when the data types are incompatible, or when the relational operator is invalid for the current situation or unrecognized.

logWorkingMemory

protected void logWorkingMemory()

Write the contents of working memory out to the Inference trace log. Trace logging is presumed on.

logConflictSet

protected void logConflictSet(java.util.SortedSet conflictSet)

Write the contents of the conflict set (triggered rules) to the Inference trace log

addRuleToConflictSet

public boolean addRuleToConflictSet(AblePatternMatchRule theRule)

Inserts the Rule into the conflict set based on priority and specificity.

Parameters:

theRule - the Rule that needs to be added

Returns:

True if the rule was already in the conflict set.

removeRuleFromConflictSet

public boolean removeRuleFromConflictSet(AblePatternMatchRule theRule)

Inserts the Rule into the conflict set based on priority and specificity.

Parameters:

theRule - The Rule that needs to be removed.

setControlParameter

public void setControlParameter(java.lang.String theControlParameter,
                                java.lang.Object theValue)
                         throws AbleDataException

Set the specified control parameter on the associated inference engine.

Specified by:

setControlParameter in class AbleInferenceEngine

Throws:

AbleDataException

getControlParameter

public java.lang.Object getControlParameter(java.lang.String theControlParameter)
                                     throws AbleDataException

Returns the specified control parameter on the associated inference engine.

Specified by:

getControlParameter in class AbleInferenceEngine

Throws:

AbleDataException

allocateWorkingMemory

public AbleWorkingMemory allocateWorkingMemory()

Description copied from class: AbleInferenceEngine

Retrieve the workingMemory object (may be null).

Overrides:

allocateWorkingMemory in class AbleInferenceEngine

Returns:

The current working memory, or null if no working memory exists.