ans is C operator subgoaling
If an operator has been selected but cannot be applied to the current state,
a useful strategy is to create a subgoal to find a state where the operator
can be applied. This strategy is called *operator subgoaling* (also
{precondition satisfaction}) and is a common AI technique
Goal stack planning One of the earlier planning algorithms called goal stack planning. It was used by STRIPS. We work backwards from the goal, looking for an operator which has one or more of the goal literals as one of its effects and then trying to satisfy the preconditions of the operator. The preconditions of the operator become subgoals that must be satisfied. We keep doing this until we reach the initial state. Goal stack planning uses a stack to hold goals and actions to satisfy the goals, and a knowledge base to hold the current state, action schemas and domain axioms Goal stack is like a node in a search tree; if there is a choice of action, we create branches
operator overloading is a different concepts used in OOPS
For forward search which is data oriented we starte at the initial state and compute state transitions
For backward search which is goal oriented, we start at the goal and compute inverse state transitions