When an EventExpression or PreparedEventExpressionTemplate is created or when addMatchListener() is called on an event expression within a JMon monitor the event expression is not validated immediately. It is queued for processing later when the JMon monitor yields control back to the correlator. This means that a badly formed event expression does not cause an exception to be thrown from the constructor. Instead, the correlator logs an error message later when it tries to validate the event expression.