Controlling structural resource management.  Let us turn then to the use of ◊,□ as control devices. The control can take two forms: one is to license access to a structural option that would be overgenerating if globally available; the second is to occasionally block a structural capability of the grammar. For the licensing type of control, compare the multimodal treatment of extraction in terms of a distinction ⊗c vs ⊗d, with the ◊-controlled version below, which relies on a single binary composition operation, and narrows down the ‘movement’ potential entirely to ◊-marked resources.