Re: [rules-users] Controlling Rule Execution
On 31/07/2013, jking527467 <jason.king(a)openroadsconsulting.com> wrote:
All,
I'm new to Drools and I'm faced with what seems to be a pretty trivial task
that's taken a lot longer than expected.
I'm working mainly with distances and am looking for an plain English
response to this trivial problem.
Plain English? Here is it in DRL:
rule "not active thing"
when
Range( $near: near, $far: far )
$a: Actor()
$t: Thing( ! active )
then
end
rule "activate near range"
extends "not active thing"
when
eval( isInRange( $a, $t, $near ) )
then
modify( $t ){ setActive( true ) }
end
rule "activate far range"
extends "not active thing"
when
not ( $n: Thing( isInRange( $a, $n, $near ) ) )
eval( isInRange( $a, $t, $far ) )
then
modify( $t ){ setActive( true ) }
end
Here's the problem:
- Activate all things within x miles.
- If nothing is within x miles, activate all things within y miles.
It seems pretty straight forward but here's my dilemma. If I execute on y
miles first, everything within x miles will also be activated. I need to
ensure the things between x and y miles aren't activated if anything is
within x miles of a certain fact.
Don't think in terms of "executing first" and (needlessly) exercising
control.#
As you can see from the rules, simply transform your spec into LHS
patterns. Both clauses have their one-to-one correspondence in the
second and third rule, respectively, while the first one simply
addresses the "player" facts.
-W
Does this make any sense to anyone? I'm have a hard time grasping the
proper approach and have looked into activation groups, etc. but haven't
had
any luck.
Any help is GREATLY appreciated!!!
Thanks in advance!
Jason
--
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