RootAncestor is used internally by writer objects for dealing with form inheritance. It is used to iterate through ancestor components when writing properties in inherited forms. 

RootAncestor is always the ancestor form. For each component in Root, which is the inherited form, the Ancestor property tracks a corresponding component in RootAncestor. 

The writer object iterates through each of the Root form's owned components, comparing each to the corresponding component in the RootAncestor form. It then writes only those properties in the current component that differ in some way from those in the Ancestor component. 

Ancestor 

Owner 

Root 

WriteDescendent