t b c asf friend Jane Joan Jack y Frank yar constructor some relation role_name1 role 1 constant a constant b role_name2 role 2 another relation constant c constant d yac constant g constant h empty constant h some relation role_name1 role 1 constant a constant b constant b b role_name2 role 2 another relation constant c constant d x role_name3 role 3 yet another relation constant b constant e constant b role_name3 role 3 b