a) Add an operator (action)
b) Add an ordering constraint between operators
In constructing a plan, there are typically two types of steps:
- Primitive Steps: These are basic, low-level actions that directly manipulate the environment or system. Primitive steps are typically simple and concrete actions that can be executed directly without further decomposition. For example, in a robotic navigation system, primitive steps might include moving forward a certain distance, turning left or right, or picking up an object.
- Composite Steps: These are higher-level actions that are composed of sequences of primitive steps or other composite steps. Composite steps abstract away the details of the underlying actions and provide a more abstract representation of the plan. They help in organizing and simplifying the planning process by breaking it down into manageable chunks. For example, a composite step in a cooking recipe might be “prepare ingredients”, which involves multiple primitive steps such as chopping vegetables, measuring ingredients, and preheating the oven.
In summary, while primitive steps directly interact with the environment, composite steps provide a higher-level representation of the plan by combining multiple primitive steps or other composite steps.