Basic idea: associate a Watcher with each event.<br><br>class Watcher {<br> Value what;<br> int count = 1;<br> Set<Value> valueSet = new HashSet<Value>();<br> Watcher( Value first ){<br> valueSet.add( what = first );<br>
}<br> //...<br>}<br><br>And now the rules:<br><br>rule attachWatcher<br>when<br> $event : Value(
eval(parameterValueExceededLimit($eventA.getAlarms())) )<br> not( Watcher( what == $event ) )<br>then<br> insert( new Watcher( $event ) );<br>end<br><br>rule addEvent<br>when<br> $watcher : Watcher( $eventA : what, $set : valueSet )<br>
$eventB : Value( this after[0ms,1h] $eventA &&<br>
// this != $eventA && ### set includes Watcher.what<br>
eval(valueExceededLimit($eventB.getAlarms()) && ! $set.contains( this ) ) )<br>then<br> modify( $watcher ){<br> setValueList( $watcher.getValueSet().add( $eventB ),<br> setCount( $watcher.getCount() + 1 )<br>
}<br>end<br><br>rule testLimit<br>when<br> $watcher : Watcher( count > Limit )<br>then<br> // raise hell,<br> // probably: get rid of all in $watcher.set, and $watcher<br>end<br><br>(What and count are somewhat redundant, but this avoids clumsy patterns.)<br>
<br>Watcher should be declared as Event, with @expires, so they'll disappear with the (primary) Event each one is watching.<br><br>Cheers<br>-W<br><br><br><div class="gmail_quote">2010/8/5 Tina Vießmann <span dir="ltr"><<a href="mailto:tviessmann@stud.hs-bremen.de">tviessmann@stud.hs-bremen.de</a>></span><br>
<blockquote class="gmail_quote" style="border-left: 1px solid rgb(204, 204, 204); margin: 0pt 0pt 0pt 0.8ex; padding-left: 1ex;">
<div bgcolor="#ffffff" text="#000000">
Hi,<br>
<br>
I'm working on thinking in Drools rules. Right now I'm trying to solve
this:<br>
The rule shall fire if <u>a special event occurs more than 3 times
within 1 hour</u>.<br>
<br>
My <u>first thought of a solution</u> 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?<br>
And global variables must always be initialized from outside the rules
file, don't they?<br>
<br>
Because of these thoughts I've looked for a <u>different solution
without global variables</u>. I came up with:<br>
<br>
<blockquote>function boolean valueExceededLimit(Set<Alarms>
alarmSet) {<br>
//....<br>
}<br>
<br>
rule "more than 3 occurs within 1 hour"<br>
<br>
when<br>
// event #1<br>
$eventA : Value(
eval(parameterValueExceededLimit($eventA.getAlarms())) )<br>
// event #2<br>
$eventB : Value( this after[0ms,1h] $eventA &&<br>
this != $eventA &&<br>
eval(valueExceededLimit($eventB.getAlarms())) )<br>
// event #3<br>
$eventC : Value( this after[0ms,1h] $eventA &&<br>
this != $eventA &&<br>
this != $eventB &&<br>
eval(valueExceededLimit($eventC.getAlarms())) )<br>
// event #4 -> 4 > 3<br>
$eventD : Value( this after[0ms,1h] $eventA &&<br>
this != $eventA &&<br>
this != $eventB &&<br>
this != $eventC &&<br>
eval(valueExceededLimit($eventD.getAlarms())) )<br>
<br>
then<br>
// ... do something ...<br>
<br>
end <br>
</blockquote>
<br>
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.<br>
<br>
<br>
Thanks :)<br>
Tina<br>
</div>
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<br></blockquote></div><br>