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This is the in-class activity for Thursday February 17.
The materials that you will need for this in-class activity are:

In Class Activity: Planning and PDDL

Today in class, we will look at a classical planning algorithms that use a language for defining plans called PDDL (Planning Domain Definition Language). PDDL and classic planning are all defined in the Russell and Norvig textbook AI A Modern Approach, in chapter 11. I also recommend this tutorial by Kory Becker: Artificial Intelligence Planning with STRIPS, A Gentle Introduction. She has an online demo that lets you upload your own PDDL-specified problems, and find solutions to them.

We will use this Python library:

In PDDL, we can define action schema to represent actions. Here is an example of an action schema for flying a plane from one location to another:

(:action fly
     :parameters (?p - plane ?from - airport ?to - airport)
     :precondition (and (plane ?p) (airport ?from) (airport ?to) (at ?p ?from))
     :effect (and (at ?p ?to)) (not (at ?p ?from)))
)

This defines an action called fly, which takes 3 arguments: a plane p, a starting airport from and a destination airport to. In order for this action to be applied, several preonditions must be satisified:

  1. p must be a plane
  2. from must be be an airport
  3. to must be be an airport
  4. p must initially be located at from.

Once the action is applied, then it has the effect of changing several states in the world.

  1. p is no longer located at from
  2. p is now located at to

In general, a schema consists of:

  • an action name
  • a list of all the variables use in the schema
  • a precondition - a conjunction of literals (positive or negated atomic logical sentences)
  • an effect - a conjunction of literals

Note: The enforcement of argument types like (plane ?p) can be left out of the action schema if we specify types in the domain PDDL file.

What to do

  1. Open Planning and PDDL.ipynb.
  2. Save a copy of it in your own drive by choosing File > Save a Copy in Drive from the Colab menu. This will ensure that your changes are saved.
  3. Create pairs of PDDL files for the following problems:
    • move-item-to-location
    • go-fishing
    • feed-troll If you’ve got extra time, you’re welcome to work on PDDL definitions for other parts of the Action Castle game.
  4. Please submit your work to Gradescope by Monday, February 21, 2022 before 11:59PM.