% File 'graph-description'
% Description of the graph
%        _________
%       |         |
%       |         v
%       0 -> 1 -> 2 -> 3 -> 4
%       ^                   |
%       |___________________|

:- sorts
  node.

:- objects
  0..4    :: node.

:- constants
  edge(node,node)	:: boolean.

:- variables
  X,Y			:: node.

edge(X, (X+1) mod 5).
edge(0,2).
default -edge(X,Y).	% no other edges