[rules-users] suprises when using auto-focus with salience or lock-on-active

[Olli Knuuttila]

Thank you for your fast reply.

First:

I don't want to dictate an execution order in the style of A->B->C. I want
that my agenda-groups will get focused in a predictable manner if there is a
conflict between auto-focused rules. To use the order in which they appear
in the drl-file seems to be a bit risky: this feature is not documented, it
is inconvenient to use and I can't count on it to continue working the same
way in a future version. As salience already exists, I don't see why it
couldn't be used for this purpose also. To me it would seem logical.

Second:

I must have written the second part somehow unclear. I want that the rule
that grabs the focus for the group gets fired even if it has lock-on-active
set to true. Now it just grabs the focus but doesn't fire. Using the
following example to clarify:

rule "ruleA"
agenda-group "a group"
auto-focus true
lock-on-active true
when
    Fact(name="fact1")
then
    System.out.println("ruleA fired");
end

rule "ruleB"
agenda-group "a group"
no-loop true
when
    f : Fact(name=="fact1")
then
    System.out.println("ruleB fired");
    f.setValue("new value");
    update(f);
end


Now the printed output from this is

ruleB fired

even though I would expect it to be

ruleA fired
ruleB fired

If I would put the no-loop instead of lock-on-active to ruleA, then the two
rules would get locked in an infinite dog-chasing-the-tail kinda situation.

Hopefully I managed to clarify my point.

Olli



On Tue, Dec 29, 2009 at 12:23 AM, Greg Barton <greg_barton at yahoo.com> wrote:

> First:
>
> According to the drools docs: "Only rules in the agenda group that has
> acquired the focus are allowed to fire."
>
> Salience is an inter-rule directive, affecting the execution order between
> two rules that are currently eligible to fire.  Since only one agenda-group
> can be active at once, by definition the saliences of rules in different
> groups have no bearing on each other.
>
> If you want to dictate the execution order of groups of rules I'd suggest
> using ruleflows and ruleflow-group.  With those you have far more nuance and
> control than just simple salience.  Because of that I doubt there would be
> any addition of an "agenda group salience" feature, unless you write it.
>
> Second:
>
> Did you intend to add lock-on-active to rule3?  You seem to imply that.  If
> so, and if you intend rule3 to be default salience, it makes sense that
> rule3 would fire and not rule2.  rule3 fires first because of it's higher
> salience, and then the activation of rule2 is discarded because of
> lock-on-active.  If you want rule2 to fire first, and not rule3, you will
> have to flip their salience order.  If you want both to fire, but just once,
> (unless the matched properties in the LHS are changed) then use no-loop.
>  I'm not sure from what you've written that you want another behavior.
>
> --- On Mon, 12/28/09, oknuutti <olli.knuuttila at gmail.com> wrote:
>
> > From: oknuutti <olli.knuuttila at gmail.com>
> > Subject: [rules-users] suprises when using auto-focus with salience or
> lock-on-active
> > To: rules-users at lists.jboss.org
> > Date: Monday, December 28, 2009, 4:29 AM
> >
> > While evaluating Drools 5.1.0 M1, I came across two issues
> > which strike me
> > somewhat undesirable. Maybe there's good reasons why they
> > exist; perhaps I'm
> > missing something?
> >
> > First:
> >
> > If I have two agenda groups, each with a rule that has
> > auto-focus set to
> > true and different saliences, the group which will get the
> > focus first seems
> > to be determined by the order in which the auto-focused
> > rules appear in the
> > drl-file, not by their salience.
> >
> > // example snippet:
> > rule "rule1"
> > salience 0
> > agenda-group "group1"
> > auto-focus true
> > when
> > then
> >     System.out.println("rule1 fired");
> > end
> >
> > rule "rule2"
> > salience -100
> > agenda-group "group2"
> > auto-focus true
> > when
> > then
> >     System.out.println("rule2 fired");
> > end
> >
> > // output of the example:
> > rule2 fired
> > rule1 fired
> >
> > If I change the salience of rule2 to 100 the result is
> > still the same. It
> > seems reasonable to me that the salience would be taken
> > into account also in
> > this situation.
> >
> > Second:
> >
> > This issue is with auto-focus and lock-on-active. If I add
> > "lock-on-active
> > true" to rule2 and also a third rule:
> >
> > // continuing the earlier example:
> > rule "rule3"
> > agenda-group "group2"
> > when
> > then
> >     System.out.println("rule3 fired");
> > end
> >
> > then I get the following puzzling output:
> >
> > rule3 fired
> > rule1 fired
> >
> > It seems that auto-focus activates the agenda group first
> > and then tries to
> > activate rule2 but the activation is discarded by
> > lock-on-active. I feel
> > that this is a bit too strong loop prevention. I would
> > rather see rule2
> > fired once, with no consecutive activations in the case
> > that it would have
> > some conditions that were changed by rule3.
> >
> > Any comments?
> >
> > Olli
> > --
> > View this message in context:
> http://n3.nabble.com/suprises-when-using-auto-focus-with-salience-or-lock-on-active-tp101839p101839.html
> > Sent from the Drools - User mailing list archive at
> > Nabble.com.
> > _______________________________________________
> > rules-users mailing list
> > rules-users at lists.jboss.org
> > https://lists.jboss.org/mailman/listinfo/rules-users
> >
>
>
>
>
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