Prolog

I want to make a rule dependency graph for a Prolog program. For instance, the following program


foo :- bar.
bar :- quux, coox.
baz.

would result in


depends(foo, [bar]).
depends(bar, [quux, coox]).
depends(baz, []).

(which I would turn into a graph using some graphic hackery). Any tips? (I've already read SICP.)

How many Prolog programmers does it take to change a lightbulb?