[rules-users] how to ensure that one rule only is executed once?

[Michael Anstis]

You'd need to make sure you inform the engine that Order's price has
changed:-

when
    ...
then
    modify( $o ) {
        setPrice( $o.getPrice() - 20);
    }

You could also consider using agenda-groups or lock-on-active to provide
your behaviour.

*agenda-groups
*
rule "rule 1"
//implied default agenda-group of MAIN
when
    $o : Order (amount>100 && <200);
then
    modify( $o ) {
        setPrice( $o.getPrice() - 10);
    }
    drools.setFocus("next step in calculation");
end

rule "rule 2"
//implied default agenda-group of MAIN
when
    $o:Order (amount>200);
then
    modify( $o ) {
        setPrice($o.getPrice() - 20);
    }
    drools.setFocus("next step in calculation");
end

rule "rule 3"
agenda-group "next step in calculation"
when
    $o : Order(....)
then
    ....
end

*lock-on-active*

rule "rule 1"
//implied default agenda-group of MAIN
lock-on-active true
when
    $o : Order (amount>100 && <200);
then
    modify( $o ) {
        setPrice( $o.getPrice() - 10);
    }
end

rule "rule 2"
//implied default agenda-group of MAIN
lock-on-active true
when
    $o:Order (amount>200);
then
    modify( $o ) {
        setPrice($o.getPrice() - 20);
    }
end

rule "rule 3"
agenda-group "next step in calculation"
when
    $o : Order(....)
then
    ....
end

On 18 March 2011 16:08, Gabor Szokoli <szocske at gmail.com> wrote:

> Hi,
>
> >From what I know, it's generally better to make the rules idempotent:
> In your case introduce a discountedPrice field, leaving the original
> price alone.
>
> If you insist on making it run only once instead, you can introduce a
> field or fact class to mark an order "discounted", then all
> discounting rules know to ignore it. (This gets really complicated if
> the order amount ever changes and you do need to run the discounting
> rules again.)
>
>
> Gabor
>
> 2011/3/18 yong zhao <cluncao at yahoo.com.cn>:
> > Hi
> > I just try to uses jboss rules in our projects. I met a question. for
> > example
> > package sample
> > rule "rule 1"
> > when
> >   $o:Order (amount>100 and amount<200);
> >  then
> > $o.setPrice($o.getPrice()-10);
> > end
> > rule "rule 2"
> > when
> >   $o:Order (amount>200);
> >  then
> > $o.setPrice($o.getPrice()-20);
> > end
> > if the fact , order's amount is 210. then the rule2 will be executed,
> then
> > the rule1 will be fired . I want to stop the session once some rule is
> > executed or how to control the rule flow.
> > thanks in advance
> > -Yong
> >
> >
> >
> >
> > _______________________________________________
> > rules-users mailing list
> > rules-users at lists.jboss.org
> > https://lists.jboss.org/mailman/listinfo/rules-users
> >
> >
>
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>
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