[rules-users] Detecting two instances of the same event with Fusion Rules

[Wolfgang Laun]

But

    $that : Thing(...)
    Thing( this != $that,...)

is the standard way of ensuring that a pattern matches two distinct objects
of the same class, and there is no reason why you shouldn't be able to use
it with not as well:

   $that : Thing(...)
   not ( Thing( this != $that,... ) )

"Given one Thing (with constraints...) and *not* having any *other* Thing
(with constraints...), then..."

-W


2010/5/26 Georg Maier <Georg.Maier at cjt.de>

>  Hi,
>
>
>
> I’m new to Drools and currently trying to implement some examples using CEP
> / Fusion. I got stuck on a problem to which I can’t find any solution in the
> online documentation, so I’m hoping for your help.
>
> I’m trying to write a rule, which is activated whenever a certain event
> occurs and no event of the same type occurred in the e.g. last 5 minutes (or
> just at the same time). I know how to do it if these are events of different
> types, but I can’t find any way for events of the same type. What I tried is
> something like that:
>
>
>
> $error : RouterErrorEvent ( $name : routerName ) *from* entry-point "abc"
>
> not ($otherError : RouterErrorEvent ( (*this* coincides $error) &&
> (routerName == $name) ) *from* entry-point "abc")
>
>
>
> First of all there’s the problem, that $error and $otherError will be the
> same instance if a “RouterEventError” has been inserted from the “abc” entry
> point. Adding a (this != $error) to the second, ($otherError) obviously is
> no solution to that as well.
>
> If it were two different events something like in example 2.19 would work:
>
>
>
> $error1 : ErrorOneEvent( $id : id )
>
> not ($error2 : ErrorTwoEvent( id == $id, this coincides $error1 ))
>
>
>
> I’m kinda sure I’m missing something pretty “easy” here… or is this
> approach completely wrong?
>
> As I’m aware of the fact that I couldn’t be more of a newbie J I would
> appreciate any suggestions for nice tutorials or further reading as well!
>
>
>
> Thanks in advance!
>
>
>
> Georg
>
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