Execution Cycle

The execution cycle of Teton is the main decision loop consisting of the following seven steps:
  1. Select a goal using the goal selection rules. Create an impasse if no unique selection can be found.
  2. If an operation is to be selected, select one using the operator selection rules.
  3. If the selected operator has unmet preconditions, create new goals for satisfying those preconditions.
  4. If the operator can be assumed completed because of a shortcut condition or because its preconditions are met, then mark it complete. Go to 1.
  5. If the operation is primitive, mark it complete. Go to 1.
  6. Execute the operation. Go to 1.
The execution cycle first decides what to do by interpreting selection rules, then performs the operation by interpreting the body of the operator selected. The execution cycle will automatically create an impasses if no operator is uniquely selected. Impasses are resolved by multiple methods, including psychologically plausible ones such as simply skipping it or randomly choosing an operator. One important property of this selection method is that it is NON-LIFO, in other words any current goal can be selected for achievement, not simply the last goal created. The execution cycle also checks to see if the current goal has a shortcut condition. The presence of a shortcut condition is a flag that the goal has already been achieved, and that what the executor is now working on is what is called ' goal-reconstruction', because one or more previously accomplished goals have been forgotten. In this case the goals do not need to be executed and can simply be marked as completed.

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