begin %RECURSION%

VIEW Travel(x,y,t)

SELECT1 city1, city2, t2

FROM1 go

WHERE1 t1=0

SELECT2 tl.x, g.city2, g.t2

FROM2 Travel as tl, go as g

WHERE2 tl.y=g.city1, tl.t=g.t1

end %RECURSION%