4:15 a.m.
2010/8/5 Tina Vießmann <tviessmann(a)stud.hs-bremen.de>
Thank you for this approach, Wolfgang. That sounds great. :)
I just have some further question about your solution.
#1
I'm thinking about an approach without the need modifying things outside
the drl file. Is something like that doable?
Because I have to create the watcher class? (I don't expect it to be, but
why not ask. ;))
The DRL language provides "declare" (see Section 4.7 in the Expert manual).
Metadata is described in the Fusion manual.
#2
(What and count are somewhat redundant, but this avoids clumsy patterns.)
Am I right that what and count have to be defined as global variables and
initialized using setGlobal() (from a part of the java application)?
No! See the Java snippet "class Watcher". (If you use declare, you'll have
to do the initializations after creation.)
#3
rule addEvent
when
$watcher : Watcher( $eventA : what, $set : valueSet )
$eventB : Value( this after[0ms,1h] $eventA &&
// this != $eventA && ### set
includes Watcher.what
eval(valueExceededLimit($eventB.getAlarms()) && ! $set.contains( this ) ) )
I'm sorry, could you explain to me the part of $eventB in sentences,
please? I've got confused by the comments... :(
If there is
a Watcher watching $eventA and with a set of related events $set,
and
a Value less than 1hr later than $eventA and with more alarms than limit and
Watcher's $set does not contain this Value
then...
The line I commented out isn't necessary as I propose to add the very 1st
event tied to the Watcher to this Watcher's list.
Thank you very much! :)
You're welcome.
-W
Tina
Basic idea: associate a Watcher with each event.
class Watcher {
Value what;
int count = 1;
Set<Value> valueSet = new HashSet<Value>();
Watcher( Value first ){
valueSet.add( what = first );
}
//...
}
And now the rules:
rule attachWatcher
when
$event : Value( eval(parameterValueExceededLimit($eventA.getAlarms())) )
not( Watcher( what == $event ) )
then
insert( new Watcher( $event ) );
end
rule addEvent
when
$watcher : Watcher( $eventA : what, $set : valueSet )
$eventB : Value( this after[0ms,1h] $eventA &&
// this != $eventA && ### set
includes Watcher.what
eval(valueExceededLimit($eventB.getAlarms()) && ! $set.contains( this ) ) )
then
modify( $watcher ){
setValueList( $watcher.getValueSet().add( $eventB ),
setCount( $watcher.getCount() + 1 )
}
end
rule testLimit
when
$watcher : Watcher( count > Limit )
then
// raise hell,
// probably: get rid of all in $watcher.set, and $watcher
end
(What and count are somewhat redundant, but this avoids clumsy patterns.)
Watcher should be declared as Event, with @expires, so they'll disappear
with the (primary) Event each one is watching.
Cheers
-W
2010/8/5 Tina Vießmann <tviessmann(a)stud.hs-bremen.de>
> Hi,
>
> I'm working on thinking in Drools rules. Right now I'm trying to solve
> this:
> The rule shall fire if *a special event occurs more than 3 times within
> 1 hour*.
>
> My *first thought of a solution* was to count the count the detected
> events using a counter. But the counter has to be a global variable, hasn't
> it? And global variables are not to be used to frequently, aren't they?
> And global variables must always be initialized from outside the rules
> file, don't they?
>
> Because of these thoughts I've looked for a *different solution without
> global variables*. I came up with:
>
> function boolean valueExceededLimit(Set<Alarms> alarmSet) {
> //....
> }
>
> rule "more than 3 occurs within 1 hour"
>
> when
> // event #1
> $eventA : Value(
> eval(parameterValueExceededLimit($eventA.getAlarms())) )
> // event #2
> $eventB : Value( this after[0ms,1h] $eventA &&
> this != $eventA &&
>
> eval(valueExceededLimit($eventB.getAlarms())) )
> // event #3
> $eventC : Value( this after[0ms,1h] $eventA &&
> this != $eventA &&
> this != $eventB &&
>
> eval(valueExceededLimit($eventC.getAlarms())) )
> // event #4 -> 4 > 3
> $eventD : Value( this after[0ms,1h] $eventA &&
> this != $eventA &&
> this != $eventB &&
> this != $eventC &&
>
> eval(valueExceededLimit($eventD.getAlarms())) )
>
> then
> // ... do something ...
>
> end
>
>
> More than 3 is kind of a doable task. But I think of this solution as
> heavy in case its needed to detect a larger number of events. I would be
> thankful for other approaches to the problem.
>
>
> Thanks :)
> Tina
>
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>
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