Whenever a language has both a more explicit and less explicit way of forming relative clauses, then the more explicit type will be used lower down the hierarchy and the less explicit type higher up the hierarchy.
Standardized
IF there are two ways of forming relative clauses, THEN the more explicit type will be used lower down the hierarchy and the less explicit type higher up the hierarchy.
The generalization has a functional basis: the more difficult a position is to relativize, the more explicit indication is given of what position is being relativized, to facilitate recovery of this information.
The generalization has a functional basis: the more difficult a position is to relativize, the more explicit indication is given of what position is being relativized, to facilitate recovery of this information.