A relative clause of this kind, as in '(a) [the pobble] who had no toes', is reffered to as a DEFINING RELATIVE CLAUSE. All defining relative clauses are embedded and function as Qualifier in either a nominal or an adverbial group. They contrast with NON–DEFINING RELATIVE CLAUSES, which do not function as Qualifier and are not embedded. - Halliday (1985), a pag.167