There's a lot more to be said about planning.

Planning is an important real-world problem.

You can imagine that all kinds of people have thought about it.

We've essentially looked at very simple backtracking search as an algorithm.

There are other possibilities to do planning.

You can transform to SAT.

You can transform into first-order logic, describing the worlds and describing adds and deletes in first-order logic.

You can do theoretical computer science, doing things with graphs. There's an algorithm called GraphPlan, which has good properties.

I'm not going to go all into this. I'd rather discuss what the limitations are and how you get around those.