graphviz directed graph with parents at top -

this directed graph

digraph g {     semigroup     monoid -> semigroup     band -> semigroup } 

renders dot as

but want semigroup @ top. have bigger example this, hacks using rank aren't going work. general theme want arrows point upwards instead of downwards.

i tried using -y parameter, makes no difference.

if use <- in file getting top/down order correct, i'd need way reverse drawing of arrow.

you add graph

    rankdir = bt;