A man in a blue shirt is writing sentences on a chalkboard.
A man is standing in front of the class writing on a chalkboard.
A man writing sentences on a chalkboard is too old to be a student. He is a teacher, standing in front of the class.
exists e1 s1 x1 x2 x3 x4.(on(e1,x4) & n_chalkboard(x4) & Theme(e1,x3) & Actor(e1,x1) & v_write(e1) & n_sentence(x3) & in(x1,x2) & n_shirt(x2) & a_blue(s1) & Theme(s1,x2) & n_man(x1))
exists e1 x1 x2 x3 x4 x5.(n_writing(x3) & of(x3,x4) & n_class(x4) & on(e1,x5) & n_chalkboard(x5) & in(e1,x2) & of(x2,x3) & n_front(x2) & Actor(e1,x1) & v_stand(e1) & n_man(x1))