1 % nodes and values
   2 node(X) :- edge(X,Y).
   3 node(Y) :- edge(X,Y).
   4 num_edges(N) :- N = #sum { 1 : edge(X,Y) }.
   5 num(0).
   6 num(N) :- num(N1), N=N1+1, num_edges(E), N<=E.
   7 
   8 % assignment to nodes
   9 { value(X,N) : num(N) } = 1 :- node(X).
  10 
  11 % assignment to edges
  12 { edge_value(edge(X,Y),N) : num(N), N>0 } = 1 :- edge(X,Y).
  13 
  14 % relates node values with edge values
  15 :- not edge_value(edge(X,Y),M-N), edge(X,Y), value(X,M), value(Y,N), N < M.
  16 :- not edge_value(edge(X,Y),N-M), edge(X,Y), value(X,M), value(Y,N), N > M.
  17 
  18 % alldifferent values
  19 :- value(X,N), value(Y,N), num(N), X<Y.
  20 :- edge_value(X,N), edge_value(Y,N), num(N), X<Y.