Two models are sequential by nature if the first model necessarily waits while the second model is running, and vice-versa. The sequence is imposed by the exchange of coupling fields.
Two models are concurrent by nature if coupling data produced by one model depend on other coupling data produced previously by the other model during the same coupling timestep, and vice-versa.
Two models are concurrent by construction if they are sequential by nature but forced to run concurrently. This requires, at a given timestep, that coupling data produced at the preceding timestep are used as input.
Two models are sequential by construction if they are concurrent by nature but forced to run sequentially. This requires, at a given timestep, that coupling data produced at the preceding timestep are used as input.
