[rules-users] How to traverse a hierarchy?

[Charles Binford]

Greg,  I'm trying to test this out but am having trouble getting things
to run.  I'm not very experienced with java so I may be doing something
stupid on that side of things also.  Here are the key parts of what I
have and the results I'm getting:

In my class called File I have the following:
    public int[] classState = new int[] {0,0,0,0,0,0,0,0,0,0};
....
    public void setClassState(int idx, int val) {
        int oldState = classState[idx];
        if (oldState != val) {
            classState[idx] = val;
            changes.firePropertyChange("classState", oldState,
                classState);
        }
    }


In my drl file:
rule "user rule 1.1"
     agenda-group "classify"
     salience 3
     dialect "java"
     when
        $f : File(classState[0] == 1, classState[1] == 0 )
     then
    // do stuff
   $f.setClassState(1,1);
end

AND the error I get when I run....

org.drools.RuntimeDroolsException: Exception executing predicate eval(
classState[0] == 1 )
    at
org.drools.rule.PredicateConstraint.isAllowed(PredicateConstraint.java:216)
    at org.drools.reteoo.AlphaNode.assertObject(AlphaNode.java:137)
.....
Caused by: org.mvel.CompileException: illegal use of []: unknown type: null

Charles Binford

Greg Barton wrote:
> Edson's advice on this issue is spot on, but if you want a more incremental approach you may try this: optimize your hierarchy test.  A regex string match is not the fastest thing you could do to check what level the rule is in, and that test is the one done most frequently. (It's in every rule, and should be the first condition in the LHS, right?)  So some targetted optimization, if possible, could be helpful.  Could the hierarchy indicator be an array of integers?  The test for integer equality is orders of magnitude faster than regex.
>
> when
>     obj(level[0] == 1, level[1] == 2, level[2] == -1) //-1 indicates unset
>     ...
> then
>     objSetLevel(2, 1); //Set level[2] == 1
>     ....
> end
>
> Yes, messy looking, but probably a lot faster than regex.
>
> And as for the "changing the contents of the object and doing the update is not good for drools performance" idea, I guess it matters what your purpose is.  Changing the contents of objects and having the rules react to that change is what rules are for. :)  If this is something you intend to avoid you might want to look at sequential mode processing.
>
> --- On Mon, 4/13/09, Charles Binford <Charles.Binford at sun.com> wrote:
>
>   
>> From: Charles Binford <Charles.Binford at sun.com>
>> Subject: [rules-users] How to traverse a hierarchy?
>> To: "Rules Users List" <rules-users at lists.jboss.org>
>> Date: Monday, April 13, 2009, 4:56 PM
>> All,  I'm trying to figure out a better way to solve
>> this problem.  I
>> have a batch of objects that I want matched against a
>> hierarchy of
>> rules.  I check the rules in order, and as soon as I find a
>> match I'm
>> done for that level of the hierarchy.  In other words, If
>> the object
>> matches a rule, we'll check the rules children, but not
>> the siblings. 
>> Example:
>>
>> rule 1
>>   rule 1.1
>>   rule 1.2
>>     rule 1.2.1
>>     rule 1.2.2
>>   rule 1.3
>> rule 2
>>
>> If an object matches rule 1, check for a match at level
>> "1.*", but rule
>> 2 will never be checked.  If an object matches 1, 1.2, and
>> 1.2.1, we're
>> done as 1.2.1 has no children.
>>
>> My current implementation with drools works, but is very
>> inefficient.  I
>> have a "level" string in the objects and whenever
>> I find a match I
>> update the level of the object and force an object update. 
>> Each rule
>> tests that the level string is correct, e.g. rule 1.2.1
>> works as follows:
>> rule "1.2.1"
>> when
>>     obj(level matches "1.2.*",.....)
>>     ...
>> then
>>     objSetLevel("1.2.1.*");
>>     ....
>> end
>>  
>> I'm also using saliance to keep the evaluation order
>> like I want it.
>>
>> Changing the contents of the object and doing the update is
>> not good for
>> drools performance as I understand it so I'm looking
>> for a better way. 
>> The hierarchy and the order of the matching is key to my
>> application so
>> I'm not wanting to redesign that part of things. 
>>
>> I tried using activation-groups.  That worked great as long
>> as I only
>> had a single object to run through the hierarchy, but given
>> the way the
>> rest of the system is design I need to load up 10-100
>> objects before
>> each call to fireallrules() for performance purposes.
>>
>> Any suggestions are appreciated.
>>
>> Charles Binford
>>
>>
>> _______________________________________________
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>> rules-users at lists.jboss.org
>> https://lists.jboss.org/mailman/listinfo/rules-users
>>     
>
>
>       
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