When the type attribute is VARSTRING, the value attribute is a String with predefined variables that is substituted using the “arg” node. For example, you could have a Property with a type equal to VARSTRING, and a value equal to “Device {0} deleted from Network {1}”.

The “arg”s defined inside the property node defines how attributes {0} and {1} are evaluated. Arguments follow the same style as property nodes. The types that are allowed for Arg nodes are CONSTANT and XPATH.

For Example:

<Transform eventName = "DeviceDeleteEvent">
      <Property name="EVENTSTRING" type="VARSTRING" 
value="Device {0} deleted from Network {1}">
<arg key="0" value="/VoyenceEvent/Device/DeviceDeleteEvent/DeviceId/Name"/>
<arg key="1" value="/VoyenceEvent/Device/DeviceDeleteEvent/NetworkId/Name"/>