DBFieldDef :: get_depend - DEPENDENT option
This option marks the instances in the collection as dependent. When this option is set, referenced instances are deleted when being removed from the reference, although the reference is not marked as owner of the instances.
References are by definitions depend. For relationships, which are not depend by definition, this option can be set explicitly. The option need not to be set for owning relationships or references.
The value YES means that all instances referenced by the relationship depends on the relationship and will be deleted, when they are removed from the relationship ( SDB_Relationship :: depend ).