Any help with the query below would be much appreciated. I am assuming that
event retraction is not automatic using the pattern below, however I am
trying to come by an approach to ensuring only one event exists on an entry
point at any moment in time. One thought was that when a rule inserts a new
event, it first retracts the previous event, although I think that a rule
cannot have state and can therefore not maintain a handle to the previously
inserted event?

But a fact can have state. Event() is the event.

declare Window
event: Event
end

rule createWindow
when
$e: Event()
not Window()
then
insert( new Window( $e ) );
end

rule pushWindow
when
$e: Event()
$w: Window()
then
retract( kcontext.getKnowledgeRuntime().getFactHandle( $e.getEvent() ) );
modify( $w ){ setWindow( $e ) );
end

-W

What would be a good approach to achieving this?

Many thanks,

James

jwillans2 wrote:
>
> Hello,
>
> I am using sliding windows in the form:
>
> Obj(..) over window:length(1) from entry-point EP1
>
> Where many events are being inserted into EP1. Reading the documentation
> I expected Drools to infer from the window length that all events on EP1
> apart from the latest one can be retracted, is this correct? The reason I
> ask is that I am not seeing retraction of events from EP1 when I debug the
> session, and I am see behaviour which suggests the rule is firing against
> old events on the entry point.
>
> Basically I want to get to simulate that an entry point can only contain
> one event at any point in time and that this event is the latest one to
> arrive.
>
> Thanks,
>
> James
>

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