.. index:: Property Property ======== This is the name of the property to be replaced. It can be any property that a given event posses. If a property is selected that is empty for the event processed, an empty string is returned. A property is either an :doc:`event property <../references/eventproperties>`, a :doc:`custom property <../references/customproperties>`, a dynamic property or a :doc:`system property <../references/systemproperties>`. If a property is selected that is not present, the result will always be an empty string, no matter which other options have been selected.