before or after within variable window?

I am trying to design a rule system where the rules themselves can be external configured, using a rule configuration object. Specifically, I want to configure externally to the DRL rule definition what the minimum time between rule firings for a particular type of rule should be.

My approach so far is to insert the rule configuration as a fact ValueRuleSpec:

rule "Any value detected"
when
    $r : ValueRuleSpec(mode == ValueRuleSpecMode.ANY(), $devices: devices)
    $e : SensorEvent(deviceId memberOf $devices) from entry-point FMSensorEvents
    not Activation(ruleSpec == $r, cause == $e)
then
    insert(new Activation($r, $e));
end

The $r ValueRuleSpec object has a property triggerEvery that contains the minimum number of seconds between activations. I know that this can be done statically by testing for the absence of an Activation object that is inside a specific range before $e using something like:

not Activation(this before[60s, 0s] $e)

How could I do this with a configurable time window, using the $r.triggerEvery property as the number of seconds?

Solution

Answering my own question based on the advice of laune.

The before keyword's behavior is described in the manual as:

$eventA : EventA( this before[ 3m30s, 4m ] $eventB ) 
The previous pattern will match if and only if the temporal distance between the time when $eventA finished and the time when $eventB started is between ( 3 minutes and 30 seconds ) and ( 4 minutes ). In other words:
3m30s <= $eventB.startTimestamp - $eventA.endTimeStamp <= 4m

Looking up the source code for the before evaluator we can see the same.

 @Override
 protected boolean evaluate(long rightTS, long leftTS) {
     long dist = leftTS - rightTS;
     return this.getOperator().isNegated() ^ (dist >= this.initRange && dist <= this.finalRange);
 }

Based on this I've modified my code accordingly, and it seems to work correctly now:

rule "Any value detected"
when
    $r : ValueRuleSpec(mode == ValueRuleSpecMode.ANY(), $devices: devices)
    $e : SensorEvent(deviceId memberOf $devices) from entry-point FMSensorEvents
    not Activation(ruleSpec == $r, cause == $e)
    // no activation within past triggerEvery seconds for same device
    not Activation(
        ruleSpec == $r, 
        deviceId == $e.deviceId, 
        start.time > ($e.start.time - ($r.triggerEvery * 1000))
    )
then
    insert(new Activation($r, $e));
end