похоже, что будет работать
rule "deltas"
dialect "mvel"
salience 1000
when
$sQ : MyEvent($id1 : Id) from entry-point MyEventStream
$sQ2 : MyEvent($id2 : Id, $id1 == $id2 - 1) from entry-point MyEventStream
then
System.out.println( "Associated event " + $id1 + " with event " + $id2);
end