Build control on top of functionality.

• When static measures do not suffice to isolate unwanted interactions, then components must implement dynamic control.
• Deal with aliasing -- unless statically disallowed, assume that any two references could refer to the same component.
• Deal with interference -- unless statically disallowed, assume that any two components may interefere with each other's operations.
• Place coordination at the lowest layer in which it can be managed.