[jboss-jira] [JBoss JIRA] Created: (JBRULES-1511) Can only reason over sub-objects if you use the From Conditional Element

[Aaron Dixon (JIRA)]

Can only reason over sub-objects if you use the From Conditional Element
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                 Key: JBRULES-1511
                 URL: http://jira.jboss.com/jira/browse/JBRULES-1511
             Project: JBoss Drools
          Issue Type: Bug
      Security Level: Public (Everyone can see)
          Components: Reteoo
    Affects Versions: 4.0.4
            Reporter: Aaron Dixon
         Assigned To: Mark Proctor


It appears that you MUST use the From Condition Element to reason over sub-objects or else Drools yields unpredictable behavior.

The first two rules below appear to be semantically equivalent. However the "bad" rule (the rule that does not use the from conditional element) does not get activated correctly when there is another rule (see the third rule) that modifies the age sub-property before the first two rules are activated:

rule "Older than 20 - Good"
salience -100
when
	person : Person( )
	Details( age > 20 ) from person.details
then
	System.out.println( "Older than 20 (good) : " + person );
end

rule "Older than 20 - Bad"
salience -100
when
	person : Person( details.age > 20 )
then
	System.out.println( "Older than 20 (bad) : " + person );
end

rule "30 is the new 20"
when
	person : Person( details.age == 30 )
then
	person.getDetails().setAge( 20 );
	System.out.println( "Now 20 : " + person );
	update( person );
end


Given that the "bad" rule is semantically equivalent to the second rule, Drools should treat both rules the same in the engine. See the referenced forum thread for further justification for this claim.

Also, see the attached zip for an executable example.



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