[rules-users] Erratic behaviour of Drools
Poissy.B
poissy.b at gmail.com
Mon Jun 16 00:16:48 EDT 2014
Thanks a lot for your explanations.
I think a good rule of thumb for a Drools beginner like myself is to use a
modify{} whenever I modify a fact in the working memory and use
@PropertyReactive and @watch to tweak performance.
Thanks again.
On Mon, Jun 16, 2014 at 12:05 AM, Wolfgang Laun <wolfgang.laun at gmail.com>
wrote:
> The basic rule is this: If modify is called on a fact it causes
> reevaluation of all LHSs where facts of that type are used.
>
> You may omit modify if the change does not have any effect on the
> logic, and you may omit it if this particular change should be hidden
> from the engine. (There's the use case of collecting facts A in a
> Collection property of fact B with a rule combining a (new) A with a
> B: clearly, modify of B would cause the rule to fire over and over
> again, which might be prevented using no-loop - but other occurrences
> of B might be reevaluated, too.)
>
> A more selective reaction to modification is possible using the
> "property reactive" feature - see the docs.
>
> -W
>
>
>
> On 15/06/2014, Poissy.B <poissy.b at gmail.com> wrote:
> > Thanks Wolfgang. Actually I kind of figured out how to fix it but am not
> > sure why it is fixed.
> >
> > First to explain the context, this erratic rule belongs to a rule
> > flow-group B that is executed right after another group (A).
> >
> > There is actually a rule in A that modifies $mainProcess, more
> > specifically, it adds the actual ItemAwareElements that should be
> returned
> > by the methods getGivenResources and getReceivedResources. However I did
> > not enclose that in a "modify" statement. My point was that it is useless
> > to let the WM know as that modification has no influence on group A
> rules.
> > And I was thinking that it does not even matter for group B rules as I am
> > playing with fact's internal properties and not the fact per se.
> > (specifically: a HashSet having Set values).
> >
> > I guess I was wrong assuming all this. So my question is:
> > - Do we need to use the modify statement whenever the state of an object
> > from the working memory is changed? (even if the part of the state that
> > changed is not relevant to the reasoner)
> > - In other words, can we sometimes avoid the modify when manipulating
> facts
> > to prevent the rules from being re-evaluated uselessly?
> >
> > Thanks!
> >
> >
> > On Sun, Jun 15, 2014 at 3:59 PM, Wolfgang Laun <wolfgang.laun at gmail.com>
> > wrote:
> >
> >> OK, it's a bug all right. 5.4.0 had some problems. It might be worth
> >> trying a later 5.x version.
> >> -W
> >>
> >> On 15/06/2014, Poissy.B <poissy.b at gmail.com> wrote:
> >> > Yes it does fire if I comment either of them, and I get the exact same
> >> > response.
> >> >
> >> > I am using Drools 5.4.0.Final runtime.
> >> >
> >> > Actually Products is the name property of an object of type
> >> > DataObjectReference (wich implements ItemAwareElementAdapter). The
> >> > point
> >> of
> >> > providing the output was just to show you that the
> >> > List<ItemAwareElementAdapter> returned by both getGivenResources() and
> >> > getReceivedResources() is indeed not empty so the "exists" constraint
> >> > should have been matched.
> >> >
> >> > Thanks!
> >> >
> >> >
> >> > On Sun, Jun 15, 2014 at 2:06 PM, Wolfgang Laun
> >> > <wolfgang.laun at gmail.com>
> >> > wrote:
> >> >
> >> >> See inline.
> >> >>
> >> >> On 15/06/2014, Poissy.B <poissy.b at gmail.com> wrote:
> >> >> > Hello,
> >> >> >
> >> >> > I am a little bit confused as I don't get what I am doing wrong.
> >> >> > Here
> >> >> > is
> >> >> my
> >> >> > rule:
> >> >> >
> >> >> > **************************
> >> >> > rule "Exchange Pattern"
> >> >> > when
> >> >> > $p2: ProcessAdapter()
> >> >> > $mainProcess: ProcessAdapter( isMainProcess(), this!=$p2)
> >> >> > MessageFlowAdapter ( fromProcess == $mainProcess,
> >> >> > toProcess==$p2)
> >> >> > MessageFlowAdapter ( fromProcess == $p2,
> >> >> > toProcess==$mainProcess)
> >> >> > exists ItemAwareElementAdapter( ) from
> >> >> > $mainProcess.getReceivedResources($p2)
> >> >> > exists ItemAwareElementAdapter( ) from
> >> >> > $mainProcess.getGivenResources($p2)
> >> >> > then
> >> >> > System.out.println("** FOUND EXCHANGE PATTERN betwwen
> >> >> > "+$mainProcess.getParticipant().getName()+" AND
> >> >> > "+$p2.getParticipant().getName());
> >> >> > System.out.println("Given:
> >> >> >
> >> >>
> >>
> "+$mainProcess.getGivenResources($p2)+$mainProcess.getGivenResources($p2).size());
> >> >> > System.out.println("Received:
> >> >> >
> >> >>
> >>
> "+$mainProcess.getReceivedResources($p2)+$mainProcess.getReceivedResources($p2).size());
> >> >> > System.out.println("Intersection:
> >> >> >
> >> >>
> >>
> "+$mainProcess.intersectGivenAndReceivedResourcesWithProcess($p2)+$mainProcess.intersectGivenAndReceivedResourcesWithProcess($p2).size());
> >> >> > end
> >> >> > **************************
> >> >> >
> >> >> > This rule is never fired, although I know it should.
> >> >> >
> >> >> > When I comment out the ONE OF the two "exists" constraints, I get
> >> >> > this
> >> >> > output:
> >> >>
> >> >> Does the rule fire when you comment out either "exists" conditional
> >> >> element,
> >> >> i.e., it doesn't matter which one is removed?
> >> >>
> >> >> Which Drools version are you using?
> >> >>
> >> >> -W
> >> >>
> >> >> >
> >> >> > **************************
> >> >> > ** FOUND EXCHANGE PATTERN betwwen Amazon AND Ship.Comp.
> >> >> > Given: [Products (ID:DataObjectReference_2)]1
> >> >> > Received: [Products (ID:DataObjectRefeference_GEN7)]1
> >> >> > Intersection: [Products (ID:DataObject_2)]1
> >> >> > **************************
> >> >>
> >> >> I can't say that a display of fact type "Products" is clearly
> >> >> indicating
> >> >> the
> >> >> presence of an ItemAwareElementAdapter. That said, the rule shouldn't
> >> >> fire even with a single "exists", so I assume this is an interface
> >> >> implemented
> >> >> by Products.
> >> >>
> >> >> >
> >> >> > >From the output you can see that the rule should have been fired
> >> >> > with
> >> >> the
> >> >> > two "exists" constrains as both conditions are met, but it doesn't.
> >> >> > I am kind of new to Drools so I may be doing an horrible mistake
> but
> >> >> google
> >> >> > haven't been my friend so far. Any help will be very appreciated!
> >> >> >
> >> >> > Thanks.
> >> >> > Anis
> >> >> >
> >> >> _______________________________________________
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> >> >>
> >> >
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