Kaisse (1985) presents a theory of syntax–phonology interaction whereby a rule may require one element in the environment of the rule to ccommand another element in the environment. A crucial notion in that theory, hereafter referred to as the c-command theory, is domain ccommand, which is defined as follows (Kaisse 1985: 159): In the structure [ x max … α …], X max is defined as the domain of α. Then α c-commands any β in its domain.