As stated in the previous sections, programs define how external actions passed through the backbone result in a more or less complex series of service calls, may be to the backbone functions, may be to the tasks' internal functions.

To care for this, the following program's internal structure is used so far:

The program defines all possible actions it will be reacting on.
It also defines all necessairy agents to do the service calls. There are different agenttypes for backbone functions and task functions.

An activated action activates on its turn a series of zero or more activities, each activating one single backbone function agent.
Before doing so, there might be the necessity to perform some local task functions, which is done through the activation of a task function agent per prestep.
Also afterwards there might be the nessecity to perform such functions, which is of course done by one or more poststeps.

Thus defined, the program serves as the motor behind the task when being executed by the engine.