fact: Definition dp_graph a1 a2 := In a1 DP /\ In a2 DP /\ exists p, exists s, int_red R # (sub s (rhs a1)) (sub s (shift p (lhs a2))).
imports: Coq(Lia) CoLoR(LogicUtil ATrs ListUtil RelUtil RelSub Path ARelation SN ListOccur ListNodup AShift VecUtil ASubstitution Iter Cycle)