Create a single fact, say Clock, with a field time. Assuming that this value is updated once in a while, depending on the precision with which your time supervision should work, you may then write rules such as

rule extract
when
     Clock( $time : time )
     e1 : Event (code == "LOGON", status == "ACTIVE",
            $ts: longTimeStamp < ($time - 100) )
then
     retract( e1 );
end

2009/4/30 <rsundaar@aretus.biz>
 
I have a need to "expire" some facts based on time. In other words, if an event occurs some time and if sufficient time has gone by, the fact should become inonsequential and be retracted. Here is my simple rule to do this:
 
rule"Retract expired facts"
dialect"mvel"
// salience -5
when
e1 : Event (code == "LOGON", status == "ACTIVE")
eval ((getCurrentTimeStamp ()- e1.getLongTimeStamp()) > 100)
then
System.out.println( "Retracting expired event with Timestamp: " + e1.longTimeStamp );
retract (e1);
end
 
This does not seem to work because the "eval" method does not evaluate the rule every cycle. And, there is no other change to the fact (event) to force the rule to re-evaluate the fact. Is there a way to make "eval" in the LHS evaluate every cycle? Is there any other method?
 
I would greatly appreciate any ideas.
 
Thanks,

Ravi.


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