COSC-270: Artificial Intelligence

Project 2
Spring 2022

Due: F 2/25 @ 5 PM ET
9 points

For this project, you will implement a resolution theorem prover for propositional logic.

I have divided the project into three phases:

  1. For the first phase, write the classes and methods necessary to read, parse, store, and output propositional well-formed formulas (wffs). Formulas must be stored internally as expression trees.

    The following grammar specifies the syntax for wffs.

    formula ::= '(' proposition ')'
             | '(' 'not' formula-or-proposition ')'
             | '(' 'or' formula-or-proposition formula-or-proposition ')'
             | '(' 'and' formula-or-proposition formula-or-proposition ')'
             | '(' 'cond' formula-or-proposition formula-or-proposition ')'
    formula-or-proposition ::= formula | proposition
    proposition ::= letter letters-and-digits
    letters-and-digits ::= letter-or-digit letters-and-digits | \epsilon
    letter-or-digit ::= letter | digit
    letter ::= 'a'..'z' | 'A'..'Z'
    digit ::= '0'..'9'

    Examples of wffs written in this syntax are:

    To support development, I put some starter code on cs-class. To get started, log on to cs-class and copy over the following zip file:

    cs-class-1% cd
    cs-class-1% cp ~maloofm/cosc270/ ./
    cs-class-1% unzip
    In the p2 directory, you will find a class implementation for Tokenizer and a partial implementation for Formula. The Tokenizer class demonstrates how to configure Scanner to tokenize propositional logic formulae. The directory also contains files for the two proofs we discussed in lecture, Example 1 and the proof that beggars do not ride horses. As you can see in the files, comments begin with a forward slash, formulas begin with a left parenthesis, and both are confined to a single physical line. By convention, the last formula in the file is the conclusion.

    In addition to the these proofs, you must find two additional proofs from reputable sources consisting of at least three formulas and three propositions. Include these proof files with your submission to Autolab. Naturally, I will test your program on my own set of proofs.

    For this first phase, you must implement the class Formula with the methods

    When you submit to Autolab, the autograder will call these three methods. Naturally, you will need to implement additional methods.

  2. For the second phase, implement the routines to convert wffs to clausal form. Clauses must be stored internally as expression trees or more precisely a linked list of literals. The following grammar specifies the syntax for clauses.
    clause ::= '{' literals '}'
    literals ::= literal literals-comma-separated | \epsilon
    literals-comma-separated ::= ',' literal literals-comma-separated | \epsilon
    literal ::= proposition
             | '(' 'not' proposition ')'

    You must implement

  3. Finally, implement the routines required to conduct proofs using resolution. For this final phase, you must implement so it takes a file name as a command-line argument (e.g., java Main lecture.txt), reads the formulas in the file, negates the conclusion, converts the formulas to clauses, and conducts a proof using resolution. Main.main should print the formulas, the converted clauses, and a message indicating whether the conclusion follows from the premises.

    You must implement

Include with your submission the proof files and a transcript of your program's execution for the four proofs. The transcript should be a plain ASCII file named README. In a file named HONOR, include the following statement:

In accordance with the class policies and Georgetown's Honor Code,
I certify that, with the exceptions of the class resources and those
items noted below, I have neither given nor received any assistance
on this project.


When you are ready to submit your project for grading, put your source files, Makefile, proof files, transcript, and honor statement in a zip file named Upload the zip file to Autolab using the assignment p2. Make sure you remove all debugging output before submitting.

Plan B

If Autolab is down, upload your zip file to Canvas.

Copyright © 2022 Mark Maloof. All Rights Reserved. This material may not be published, broadcast, rewritten, or redistributed.