A little boy with rain boots takes a walk in the park.
A little boy with rain boots takes a walk in the park because he is lost from his mother.
The motivation of the boy in the park can be many things, not just because he is lost from his mother.  The boy may or may not be lost.  The boy may or may not have a living mother he can be lost from.
exists e1 s1 x1 x2 x3 x4 x5.(n_park(x5) & in(e1,x5) & Theme(e1,x4) & Actor(e1,x1) & v_take(e1) & n_walk(x4) & with(x1,x2) & n_boot(x2) & of(x2,x3) & n_rain(x3) & n_boy(x1) & a_little(s1) & Theme(s1,x1))
exists e1 p1 s1 x1 x2 x3 x4 x5 x6.(n_mother(x6) & of(x6,x5) & n_male(x5) & n_male(x5) & n_park(x5) & exists e2.(from(e2,x6) & Theme(e2,x5) & v_lose(e2)) & because(e1,p1) & in(e1,x5) & Theme(e1,x4) & Actor(e1,x1) & v_take(e1) & n_walk(x4) & with(x1,x2) & n_boot(x2) & of(x2,x3) & n_rain(x3) & n_boy(x1) & a_little(s1) & Theme(s1,x1))