People gather at a roadside park with motorcycles.
A group of bikers are celebrating at a festival.
Not all gathered people with motorcycles are a group of bikers, and we can't assume that they are celebrating at a festival.
exists e1 x1 x2 x3 x4.(at(e1,x2) & with(x2,x4) & n_motorcycle(x4) & n_park(x2) & of(x2,x3) & n_roadside(x3) & Actor(e1,x1) & v_gather(e1) & n_people(x1))
exists e1 x1 x2 x3.(at(e1,x3) & n_festival(x3) & Actor(e1,x1) & v_celebrate(e1) & of(x1,x2) & n_biker(x2) & n_group(x1))