A man is skateboarding in front of a group of people.
A man riding a bike.
A man cannot be skateboarding while riding a bike.
exists e1 x1 x2 x3 x4.(in(e1,x2) & of(x2,x3) & of(x3,x4) & n_people(x4) & n_group(x3) & n_front(x2) & Actor(e1,x1) & v_skateboard(e1) & n_man(x1))
exists e1 x1 x2 x3.(a_topic(x1) & Theme(e1,x3) & Actor(e1,x2) & v_ride(e1) & n_bike(x3) & (x1 = x2) & n_man(x1))