Module Type KNOT_BASIC.
Declare Module KI:KNOT_FULL_BASIC_INPUT.
Parameter knot: Type.
Parameter ageable_knot : ageable knot.
Existing Instance ageable_knot.
Parameter predicate: Type.
Parameter squash : (nat * F predicate) -> knot.
Parameter unsquash : knot -> (nat * F predicate).
Parameter approx : nat -> predicate -> predicate.

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