People in costumes are walking around in the street.
People are celebrating halloween
People in costumes walking around in the street  are not always celebrating halloween.
exists e1 p1 x1 x2 x3.(n_street(x3) & in(e1,x3) & exists s1.(Theme(s1,x1) & a_around(s1)) & Topic(e1,p1) & Actor(e1,x1) & v_walk(e1) & in(x1,x2) & n_costume(x2) & n_people(x1))
exists e1 x1 x2.(Theme(e1,x2) & Actor(e1,x1) & v_celebrate(e1) & n_halloween(x2) & n_people(x1))