Cranes work on the frame of a building under construction.
A building is under construction.
in both sentences, there is a building under construction.
exists x1 x2 x3 x4 x5.(n_frame(x3) & a_topic(x1) & on(x1,x3) & of(x3,x4) & under(x4,x5) & n_construction(x5) & n_building(x4) & n_work(x1) & (x1 = x2) & ne_nam_cranes(x2))
exists p1 x1.(exists x2.(under(x1,x2) & n_construction(x2)) & n_building(x1))