Existing Instance ageable_knot.
Definition knot_rel (k1 k2:knot) :=
let (n,f) := unsquash k1 in
let (n',f') := unsquash k2 in
n = n' /\ Rel predicate predicate f f'.

Lemma knot_level : forall k:knot,
level k = fst (unsquash k).