I'm playing with Drools Fusion 5.1.1 a bit to try and evaluate whether it is an appropriate tool for a project I'm working on. As part of that, I'm playing a bit with its event capabilities, but I'm running into a problem and I'm not sure whether its a bug or something that I'm doing.

I'm trying to write a rule that looks for a series of two events and I want to preclude another specific type of event from coming between the two. I've tried a couple of ways of doing this, and am now trying to use a sliding window with the following rule:

declare Event
	@role(event)
	@expires(30ms)
end

rule TestWindow
	when
		$up : Event (type == "linkup", $inf : extra)
		$window : ArrayList () from collect (
			Event (extra == $inf) over window:length(2))
		$down : Event (type == "linkdown", this before $up) from $window
	then
		channels["up"].send($up);
end


This is the only rule in my knowledge base. I create a stateful session and start inserting facts into it. First a "linkdown" event and then a "linkup" event with the same "extra" value. I get the following exception when inserting the second event:

Exception in thread "main" java.lang.ClassCastException: org.drools.common.DefaultFactHandle cannot be cast to org.drools.common.EventFactHandle
	at org.drools.base.evaluators.BeforeEvaluatorDefinition$BeforeEvaluator.evaluateCachedLeft(BeforeEvaluatorDefinition.java:333)
	at org.drools.rule.VariableRestriction.isAllowedCachedLeft(VariableRestriction.java:110)
	at org.drools.rule.VariableConstraint.isAllowedCachedLeft(VariableConstraint.java:115)
	at org.drools.common.SingleBetaConstraints.isAllowedCachedLeft(SingleBetaConstraints.java:142)
	at org.drools.reteoo.FromNode.checkConstraintsAndPropagate(FromNode.java:274)
	at org.drools.reteoo.FromNode.assertLeftTuple(FromNode.java:138)
	at org.drools.reteoo.SingleLeftTupleSinkAdapter.doPropagateAssertLeftTuple(SingleLeftTupleSinkAdapter.java:189)
	at org.drools.reteoo.SingleLeftTupleSinkAdapter.propagateAssertLeftTuple(SingleLeftTupleSinkAdapter.java:64)
	at org.drools.reteoo.AccumulateNode.evaluateResultConstraints(AccumulateNode.java:662)
	at org.drools.reteoo.AccumulateNode.assertLeftTuple(AccumulateNode.java:181)
	at org.drools.reteoo.SingleLeftTupleSinkAdapter.doPropagateAssertLeftTuple(SingleLeftTupleSinkAdapter.java:189)
	at org.drools.reteoo.SingleLeftTupleSinkAdapter.createAndPropagateAssertLeftTuple(SingleLeftTupleSinkAdapter.java:138)
	at org.drools.reteoo.LeftInputAdapterNode.assertObject(LeftInputAdapterNode.java:148)
	at org.drools.reteoo.SingleObjectSinkAdapter.propagateAssertObject(SingleObjectSinkAdapter.java:59)
	at org.drools.reteoo.AlphaNode.assertObject(AlphaNode.java:145)
	at org.drools.reteoo.CompositeObjectSinkAdapter.doPropagateAssertObject(CompositeObjectSinkAdapter.java:450)
	at org.drools.reteoo.CompositeObjectSinkAdapter.propagateAssertObject(CompositeObjectSinkAdapter.java:368)
	at org.drools.reteoo.ObjectTypeNode.assertObject(ObjectTypeNode.java:190)
	at org.drools.reteoo.EntryPointNode.assertObject(EntryPointNode.java:145)
	at org.drools.common.AbstractWorkingMemory.insert(AbstractWorkingMemory.java:1174)
	at org.drools.common.AbstractWorkingMemory.insert(AbstractWorkingMemory.java:1123)
	at org.drools.common.AbstractWorkingMemory.insert(AbstractWorkingMemory.java:917)
	at org.drools.impl.StatefulKnowledgeSessionImpl.insert(StatefulKnowledgeSessionImpl.java:251)
	at net.wlauer.DroolsEngine.NonSpringRulesEngine.main(NonSpringRulesEngine.java:71)


Browsing the mailing list seems to indicate that this means that for some reason Drools is interpretting one of my facts as of role fact instead of role event. I'm not sure why this would be event that the only things I'm inserting are Event objects, which can be seen above to have the role of event. 

Am I doing something wrong here? Is there something wrong with my rule (and is it going to do what I think its doing)? Or have I encountered a bug with the sliding window implementation?

Any thoughts or help would be appreciated.

Will
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