On 23 March 2011 21:11, jwillans2 <span dir="ltr"><<a href="mailto:james.willans@ceteva.com">james.willans@ceteva.com</a>></span> wrote:<br><div class="gmail_quote"><blockquote class="gmail_quote" style="border-left: 1px solid rgb(204, 204, 204); margin: 0pt 0pt 0pt 0.8ex; padding-left: 1ex;">
Any help with the query below would be much appreciated. I am assuming that<br>
event retraction is not automatic using the pattern below, however I am<br>
trying to come by an approach to ensuring only one event exists on an entry<br>
point at any moment in time. One thought was that when a rule inserts a new<br>
event, it first retracts the previous event, although I think that a rule<br>
cannot have state and can therefore not maintain a handle to the previously<br>
inserted event?</blockquote><div><br>But a fact can have state. Event() is the event.<br><br>declare Window<br> event: Event<br>end<br><br>rule createWindow<br>when<br> $e: Event()<br> not Window()<br>then<br> insert( new Window( $e ) );<br>
end<br><br>rule pushWindow<br>when<br> $e: Event()<br>
$w: Window()<br>
then<br> retract( kcontext.getKnowledgeRuntime().getFactHandle( $e.getEvent() ) );<br>
modify( $w ){ setWindow( $e ) );<br>
end<br><br>-W<br><br><br><br> </div><blockquote class="gmail_quote" style="border-left: 1px solid rgb(204, 204, 204); margin: 0pt 0pt 0pt 0.8ex; padding-left: 1ex;"> What would be a good approach to achieving this?<br>
<br>
Many thanks,<br>
<br>
James<br>
<br>
<br>
jwillans2 wrote:<br>
><br>
> Hello,<br>
><br>
> I am using sliding windows in the form:<br>
><br>
> Obj(..) over window:length(1) from entry-point EP1<br>
><br>
> Where many events are being inserted into EP1. Reading the documentation<br>
> I expected Drools to infer from the window length that all events on EP1<br>
> apart from the latest one can be retracted, is this correct? The reason I<br>
> ask is that I am not seeing retraction of events from EP1 when I debug the<br>
> session, and I am see behaviour which suggests the rule is firing against<br>
> old events on the entry point.<br>
><br>
> Basically I want to get to simulate that an entry point can only contain<br>
> one event at any point in time and that this event is the latest one to<br>
> arrive.<br>
><br>
> Thanks,<br>
><br>
> James<br>
><br>
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