Some researchers believe that a general executive function for an AI requires a "hardware solution," a specialized module as a part of the AI's cognitive architecture. (see the work of Dario D. Salvucci, for example) One argument in favor of this view is the belief that procedural knowledge and control processes are handled in different segments of the human brain, basal ganglia versus dorsolateral prefrontal cortex.
As a simple example of executive control, executive processes might pick the most activated schema and cause it to take control of cognition. Things get more difficult in situations where multitasking is required.
Other researchers believe that a general executive function might result from simply making task goals another element in working memory. In rule based systems, for example, one set of rules can control other rules by modifying the goals that are currently active in memory. (see the work of David Kieras for example) One argument in support of this view is the fact that modern computer operating system development typically minimizes the use of "hardware fixes" in dealing with control issues. (things like interrupt hardware)
This is all related to the question of what consciousness is and how it works, both in humans and in machines.