Reasonning with Interface

[Jonathan MERCIER]

Dear,

Drools require to follow Java convention as example a fields name has a method getName(). With complex data model is interesting to put inside Interface a standardized way to communicate.

Interface Human extends Walkable, Speakable {
    String getName();
}

Interface Walkable{
    int speed;
    int[3] getPosition(); // x,y,z
    void move( int speed );
}

class Person implements Human {
    String name;
    int[3] position;
 ....
}

and reasonning by contract with Interface

rule "Human  walk"
  when
    $h : Human( speed > 0)
  then
   System.out.println( $h.getName() + " " + "walk" );
end


this do not work because drools try to find the name fields in Human definition intead of the Human instance.


Someone could say, how doing this in drools ?

I do not want to have all Object with a deep inheritance to do this.

regards
  

[Mark Proctor]

I’m not really understanding what you mean in the last 3 sentence.

Drools expects JavaBeans, so those interfaces will need to obey JavaBean specs for setters and getters. If it obeys the spec, it should work.

Mark

regards
  

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[Davide Sottara]

I agree with Mark, this use case should work. if you are getting errors, could you provide the stack trace and, possibly, a reproducer?

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[Jonathan MERCIER]

I though using interface worked before. Firslty I though I done a mistake somewhere but I see nothing abnormal and when I use the class instead of the Knowledge interface that build.

My code:

public interface Fact {
    public Observation  getObservation();
    public String       getName();
    public String       getSource();
    public void         setObservation(final Observation o);
    public void         setName(final String n);
    public void         setSource(final String s);
}

public interface Knowledge extends Fact{
    public Constraint          getConstraint();
    public List<Knowledge>     subKnowledges();
    public Knowledge           partOf();
    public int                 getGroup();
    public Conclusion          getConclusion();
    public void                setConstraint(final Constraint c );
    public void                setSubKnowledges(final List<Knowledge> lk);
    public void                setPartOf(final Knowledge k );
    public void                setConclusion(final Conclusion c );
    public void                setGroup(final int g );
    public void                add(final Knowledge k);
}

basic rules:
rule "Result infer to a knowledge not yet checked"
    when
        $k: Knowledge( observation == Observation.UNKNOWN )
        $r: Result( name == $k.name, observation != Observation.UNKNOWN )
    then
        $k.observation = $r.observation;
        update( $k );
        System.out.println($k.name +" "+ $k.observation + " " + $k.conclusion );
        System.out.println($r.name +" "+ $r.observation );
        //kieSession.getAgenda().getAgendaGroup( "conclusion" )
end

Stack trace:

java.lang.RuntimeException: Error while creating KieBase[Message [id=1, level=ERROR, path=fr/cea/ig/labgem/brools/biology/knowledge_reasoner.drl, line=48, column=0
   text=Rule Compilation error observation cannot be resolved or is not a field
observation cannot be resolved or is not a field
name cannot be resolved or is not a field
observation cannot be resolved or is not a field
conclusion cannot be resolved or is not a field
name cannot be resolved or is not a field
observation cannot be resolved or is not a field]]
	at org.drools.compiler.kie.builder.impl.KieContainerImpl.getKieBase(KieContainerImpl.java:365)
	at org.drools.compiler.kie.builder.impl.KieContainerImpl.newKieSession(KieContainerImpl.java:514)
	at org.drools.compiler.kie.builder.impl.KieContainerImpl.newKieSession(KieContainerImpl.java:485)

[Jonathan MERCIER]

using method defined in Interface works:

rule "Result infer to a knowledge not yet checked"
    when

        $k: Knowledge( this.getObservation() == Observation.UNKNOWN )
        $r: Result( this.getName() == $k.getName(), observation != Observation.UNKNOWN )
    then
        $k.setObservation( $r.getObservation() );
        update( $k );
        //System.out.println($k.name +" "+ $k.observation + " " + $k.conclusion );
        //System.out.println($r.name +" "+ $r.observation );
        //kieSession.getAgenda().getAgendaGroup( "conclusion" )
end

As you can see I do not use fields naming but the method name, this works but I hope that is not an hided eval.

[Jonathan MERCIER]

sorry guy now that work but I do not see which change fix it, my code is close than the old one.

Thanks you a lot to have answered on my question.

Regards

[Mario Fusco]

Hi,

which version are you using? I believe this problem has been already reported here https://issues.jboss.org/browse/DROOLS-509 and fixed as demonstrated by this test case https://github.com/droolsjbpm/drools/blob/master/drools-compiler/src/test/java/org/drools/compiler/integrationtests/Misc2Test.java#L6241

Note there that the interfaces I0 and I1 are defined as it follows

public interface I0 {
    String getValue();
}
public interface I1 extends I0 { }

and the pattern in the rule does 'I1( value == \"x\" )' that looks pretty identical to your test case.

Is your test case more complex than this? If so can you provide a complete reproducer of the problem?

Thanks,
Mario

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[Jonathan MERCIER]

Yes mario that is exactly this patrtern