Materializing properties is the process to derive a value from a property path (like Property A->Property B->Property C)  and store it as an artificial property of a document instance.

To materialize a property based on the current property (i.e. the property whose control this is), a property paths must be specified that originates on the property.

$<Persons->Name>=[Hanna]
$<Persons->Address->City>=[New York]