Planning is a long-standing sub-area of Artificial Intelligence (AI). Planning is the task of finding a procedural course of action for a declaratively described system to reach its goals while optimizing overall performance measures.

Planning AI works well in system with predefined symbols: driving, legal contracts, etc. Its contextualized logic.

It’s called planning artificial intelligence because you still have to plan out how to match your symbols and patterns. Tries to solve the problem of the long lists that you get with the expert systems. Instead, it uses something called heuristic reasoning.

This reasoning gives artificial intelligence a form of common sense. It tries to limit what patterns the program has to match at any one time. This is sometimes called limiting the search space.

Google knows that there´s a limited set of choices you can choose from.
Its key to be accurate not to cumulate errors because it breaks the hole reasoning.

eg the first node expect always some constrained expression: hello, how are you, etc. so it doesn´t need to run the hole list. This is Google Places: it has all the options, but shows you the ones relevant.