Explain Goal Stack Planning.

·         In this method, the problem solver makes use of a single stack that contains both goals and operators that have been proposed to satisfy those goals.

·         The problem solver also relies on a database that describes the current situation, and a set of operators described as PRECONDITION, ADD, and DELETE lists.

·         The goal stack planning method attacks problems which involve conjoined goals. It does so, by solving the goals one at a time, in order.

·         A plan generated by this method contains a sequence of operators for attaining the first goal, followed by a complete sequence for the second goal, and so on.

    ·      At each succeeding step, the top goal on the stack will be pursued.

   

    ·         When a sequence of operators that satisfies it is found, that sequence is applied to the state description, thereby yielding new description.

·         Next, the goal that is then at the top of the stack, is explored, and an attempt is made, to satisfy it. This is done starting from the situation that was produced as a result of satisfying the first goal.

    ·         This process continues until the goal stack is empty.

   ·         Then, as one last check, the original goal is compared to the final state derived.

    ·         If any components of the goal are not satisfied in that state, then those unsolved parts of the goal are re-inserted onto the stack, and the process is resumed.