Langacker and Munro (1975) that the verb "be" in passive constructions has meanings like existential, stative, stative-existential. Langacker and Munro say that the presence of BE in the underlying structure of the passive sentences is the presence of the equivalents of 'to be' in the surface structure of the passive construction. BE refers to the constituent of the underlying structure with the meaning assigned to it by Langacker and Munro (1975:820) , viz. 'stative, existential' indicating 'existence of state'. And 'be' refers to the constituent of the surface structure. What does stative-existential meaning in the underlying structure exactly mean for passive constructions in the surface structure? It has something to do with transformational grammar. Does this mean: The stative-existential meaning assigned to "be" in the underlying (deep) structure of the passive construction influences the presence of "be" in the surface structure. The transformation from the deep structure to the surface structure is responsible for the realization of the stative-existential meaning through the explicit appearance of "be" in the passive sentence. In summary, the underlying (deep) structure influences the surface structure in transformational grammar. The stative-existential meaning associated with "be" in the deep structure of the passive construction guides the transformation process to derive the surface structure, where "be" appears, marking the passive voice. Can you please shed some light in this aspect?