People gather outdoors at a market.
The people are merchants.
People at a market could be buyers and not just merchants.
exists e1 x1 x2 x3.(at(e1,x3) & n_market(x3) & Theme(e1,x2) & Actor(e1,x1) & v_gather(e1) & n_outdoors(x2) & n_people(x1))
exists p1 x1.(n_people(x1) & exists x2.((x1 = x2) & n_merchant(x2)))