DefaultData (Storage Keyword)
The value of this element is the name of a data storage node within the current storage definition.
Specifies the name of the DATA definition that the class compiler data structure generator uses to place any previously unstored properties. A property is “unstored” if it is storable but is not listed in any DATA definition.
If you add a new, non-transient, property to a persistent class definition, and do not explicitly define a storage location for it, then the class compiler will automatically find a storage location for the property within the storage node specified by the <DefaultData> element.
The default value for the <DefaultData> element is an empty string.