Assignment 1: Symbolic Planning

In this assignment, you will use PDDL to formally define domains and problem descriptions for a planner. The goal of this exercise is to build familiarity with precise planning domain descriptions. There are three parts to this assignment, and each part will require you to create a domain definition file and a problem definition file for a total of six files (three domain definition files and three problem definition files).

Important: We will only work with the STRIPS subset of the PDDL 1.2 specifications for this assignment. The only requirement your PDDL files should include is (:requirements :strips) .

Part 1: Getting started

For this assignment, you will use the FastDownward planning system to design and test planning domains and problems. Note: version >= 23.06 compiles using the C++20 standard. The autograder runs version 22.12.

To get the planner and compile it: If you run into issues,

1. Install dependencies as listed in the FastDownard build instructions.
   • Windows users: Make sure to install the Visual Studio Build Tools Supporting C++. These are also contained in the "Desktop development with C++" workload that you can download via the Visual Studio Installer. You may also need to create a new, empty C++ project for the libraries to register.
2. Clone the code for fast-downward:

    git clone <https://github.com/aibasel/downward.git>  
    cd downward
    git checkout origin/release-22.12
   

3. Compile using the provided build script:

   ./build.py
   

   • Windows users: See the FastDownward build instructions above.

To run the planner and check the results:

1. Run the planner with a planner configuration (lama-first used here)

   ./fast-downward.py --alias lama-first {domain-file.pddl} {problem-file.pddl}
   

   For example:

    ./fast-downward.py --alias lama-first cake-domain.pddl cake-problem.pddl
   

2. If a plan is found, it will be saved in the file sas_plan by default. You can inspect the plan in the file:
   cat sas_plan

References:

• FastDownward project website: https://www.fast-downward.org/
• Repository for FastDownward: https://github.com/aibasel/downward
• FastDownward supported PDDL features list: https://planning.wiki/ref/planners/fd
• Environment setup Dependencies: https://github.com/aibasel/downward/blob/main/BUILD.md

Part 1: Complex Eat-Cake

You have been provided a cake-domain.pddl and cake-problem.pddl for the have-cake-eat-cake problem discussed in class. Modify the domain and the problem to create a more complex setting:

1. Create file, cake-complex-domain.pddl with conntent from cake-domain.pddl. Modify the domain in cake-complex-domain.pddl so that once something is baked, the dishes are dirty, and need to be cleaned using the "clean" action. The resulting plan in the simple eat-cake-have-cake problem but using this complex domain should be:

   (bake cake)  
   (eat cake)  
   (clean )  
   (bake cake)
   

   What to turn in: cake-complex-domain.pddl , which should be compatible with the original provided cake-problem.pddl .

2. Create file, cake-complex-problem.pddl with content from cake-problem.pddl. Expand the problem in cake-complex-domain.pddl to satisfy the additional objects pie and cookies, and to have a goal condition that includes eaten pie and eaten cookies.
   The initial state must be empty.
   The goal condition must be: (and (eaten cake) (eaten pie) (eaten cookies))

   What to turn in: cake-complex-problem.pddl, which should be compatible with the original provided cake-domain.pddl .

Part 2: Single-Piece King Moves

1. Create a PDDL domain definition, king in file single-king-domain.pddl, for a single king chess piece moving on an arbitrary sized board. You must use the following predicates, and no others:

• (at ?p ?x ?y) - Indicates that piece ?p is at the square ?x, ?y
• (adjacent ?y1 ?y2) - Indicates that the x- or y- coordinates ?y1, ?y2 are adjacent
• (occupied ?x ?y) - Indicates that the square ?x, ?y is occupied by another (untitled) piece The domain definition must define a move action with the following signature:

  (:action move
        :parameters (?p ?x1 ?y1 ?x2 ?y2)
  

2. Create a compatible PDDL problem definition, single-king-problem in file single-king-problem.pddl, for an 8x7 (8 squares along y direction, and 7 along x direction) board, with the following initial state:

• The king starts out from the lower left corner of the board (1, 1).
• Mark the coordinates (7,7) and (6,7) as occupied.

The final condition should be for the king to reach (7, 8) Your objects section must contain only the following:

(:objects
    king
    x1 x2 x3 x4 x5 x6 x7
    y1 y2 y3 y4 y5 y6 y7 y8
)

The domain definition must be precise enough to ensure that all valid moves are permissible and that all invalid moves are disallowed - we will test your domain definition for correctness.

What to turn in: The file single-king-domain.pddl , which defines the king's move, and the file single-king-problem.pddl that defines the above problem.

Part 3: Single-Piece Knight Moves

Create a PDDL domain definition, knight in file single-knight-domain.pddl, for a single knight chess piece moving on an arbitrary sized board. You must use the following predicates, and and no others:

• (at ?p ?x ?y) - Indicates that piece ?p is at the square ?x, ?y
• occupied ?x ?y) - Indicates that the square ?x, ?y is occupied by another (untitled) piece
• (delta1 ?y1 ?y2)- Indicates that the x- or y- coordinates ?y1, ?y2 are adjacent
• (delta2 ?y1 ?y2) - Indicates that the x- or y- coordinates ?y1, ?y2 are separated by one square

The domain definition must define a move action with the following signature:

(:action move
    :parameters (?p ?x1 ?y1 ?x2 ?y2)

2. Create a compatible PDDL problem definition, single-knight-problem in file single-knight-problem.pddl, for an 8x7 (8 squares along y direction, and 7 along x direction) board, with the following initial state:

• The knight starts out from the lower left corner of the board (1, 1).
• Mark the coordinates (2,3) and (6,6) as occupied. The final condition should be for the knight to reach (7, 8) Your objects section must contain only the following:

(:objects
    knight
    x1 x2 x3 x4 x5 x6 x7
    y1 y2 y3 y4 y5 y6 y7 y8
)

The domain definition must be precise enough to ensure that all valid moves are permissible and that all invalid moves are disallowed - we will test your domain definition for correctness.

What to turn in: The file single-knight-domain.pddl , which defines the king's move, and the file single-knight-problem.pddl that defines the above problem.

Extra Credit: Dual Knight Moves

Create a PDDL problem definition, dual-knights-problem in file dual-knights-problem.pddl, for an 8x7 (8 rows, 7 columns) board with two knight chess pieces. This problem definition must be compatible with the domain definition in part 3. Your objects section must contain only the following:

(:objects
    knight1 knight2
    x1 x2 x3 x4 x5 x6 x7
    y1 y2 y3 y4 y5 y6 y7 y8
)

The initial state must have:

• knight1 at (1,1)
• knight2 at (7,8)
• Mark the coordinates (2,3) and (6,6) as occupied. The final condition should be for knight1 and knight2 to swap positions.

What to turn in: The file dual-knights-problem.pddl , which must be compatible with your single-knight-domain.pddl from part 3.

Submission Instructions

Place the following files into a flat zip file (no directories) and submit in Gradescope under AI388U-assignment1:

1. cake-complex-domain.pddl for part 1.1
2. cake-complex-problem.pddl for part 2.2
3. single-king-domain.pddl for part 2.1
4. single-king-problem.pddl for part 2.2
5. single-knight-domain.pddl for part 3.1
6. single-knight-problem.pddl for part 3.2
7. dual-knights-problem.pddl for Extra Credit