(* Definition of the expandM modality *)
Definition knot_rel (k1 k2:knot) :=
let (n,f) := unsquash k1 in
let (n',f') := unsquash k2 in
n = n' /\ Rel assert f f'.

Axiom expandM_trans : transitive _ expandM.
Hint Resolve expandM_refl expandM_trans.