Admitted.
End TrivialSimulations.
(* NOTE: This section could be moved to where the simulations are defined. *)
Section SimulationTransitivity.

Lemma HBSimulation_transitivity:
forall G1 G2 G3 TID SCH C1 C2 C3 res,
forall (Machine1 : @machine_semantics.ConcurSemantics G1 TID SCH _ C1 mem res)
(Machine2 : @machine_semantics.ConcurSemantics G2 TID SCH _ C2 mem res)
(Machine3 : @machine_semantics.ConcurSemantics G3 TID SCH _ C3 mem res),
HybridMachine_simulation Machine1 Machine2 ->
HybridMachine_simulation Machine2 Machine3 ->
HybridMachine_simulation Machine1 Machine3.