NAME

SYNOPSIS

  use Chatbot::Eliza;

  $mybot = new Chatbot::Eliza;
  $mybot->command_interface;

  # see below for details

DESCRIPTION

This program is a faithful implementation of the program described by Weizenbaum. It uses a simplified script language (devised by Charles Hayden). The content of the script is the same as Weizenbaum's.

This module encapsulates the Eliza algorithm in the form of an object. This should make the functionality easy to incorporate in larger programs.

INSTALLATION

  http://www.perl.com/CPAN/modules/by-module/Chatbot/

To install this package, just change to the directory which you created by untarring the package, and type the following:

        perl Makefile.PL
        make test
        make
        make install

This will copy Eliza.pm to your perl library directory for use by all perl scripts. You probably must be root to do this, unless you have installed a personal copy of perl.

USAGE

        use Chatbot::Eliza;

        $mybot = new Chatbot::Eliza;
        $mybot->command_interface;

You can also customize certain features of the session:

        $myotherbot = new Chatbot::Eliza;

        $myotherbot->name( "Hortense" );
        $myotherbot->debug( 1 );

        $myotherbot->command_interface;

These lines set the name of the bot to be "Hortense" and turn on the debugging output.

When creating an Eliza object, you can specify a name and an alternative scriptfile:

        $bot = new Chatbot::Eliza "Brian", "myscript.txt";

You can also use an anonymous hash to set these parameters. Any of the fields can be initialized using this syntax:

        $bot = new Chatbot::Eliza {
                name       => "Brian", 
                scriptfile => "myscript.txt",
                debug      => 1,
                prompts_on => 1,
                memory_on  => 0,
                myrand     => 
                        sub { my $N = defined $_[0] ? $_[0] : 1;  rand($N); },
        };

If you don't specify a script file, then the new object will be initialized with a default script. The module contains this script within itself.

You can use any of the internal functions in a calling program. The code below takes an arbitrary string and retrieves the reply from the Eliza object:

        my $string = "I have too many problems.";
        my $reply  = $mybot->transform( $string );

You can easily create two bots, each with a different script, and see how they interact:

        use Chatbot::Eliza

        my ($harry, $sally, $he_says, $she_says);

        $sally = new Chatbot::Eliza "Sally", "histext.txt";
        $harry = new Chatbot::Eliza "Harry", "hertext.txt";

        $he_says  = "I am sad.";

        # Seed the random number generator.
        srand( time ^ ($$ + ($$ << 15)) );      

        while (1) {
                $she_says = $sally->transform( $he_says );
                print $sally->name, ": $she_says \n";

                $he_says  = $harry->transform( $she_says );
                print $harry->name, ": $he_says \n";
        }

Mechanically, this works well. However, it critically depends on the actual script data. Having two mock Rogerian therapists talk to each other usually does not produce any sensible conversation, of course.

After each call to the transform() method, the debugging output for that transformation is stored in a variable called $debug_text.

        my $reply      = $mybot->transform( "My foot hurts" );
        my $debugging  = $mybot->debug_text;

This feature always available, even if the instance's $debug variable is set to 0.

Calling programs can specify their own random-number generators. Use this syntax:

        $chatbot = new Chatbot::Eliza;
        $chatbot->myrand(
                sub {
                        #function goes here!
                }
        );

The custom random function should have the same prototype as perl's built-in rand() function. That is, it should take a single (numeric) expression as a parameter, and it should return a floating-point value between 0 and that number.

What this code actually does is pass a reference to an anonymous subroutine ("code reference"). Make sure you've read the perlref manpage for details on how code references actually work.

If you don't specify any custom rand function, then the Eliza object will just use the built-in rand() function.

MAIN DATA MEMBERS

METHODS

    my $chatterbot = new Chatbot::Eliza;

    my $chatterbot = new Chatbot::Eliza 'Ahmad', 'myfile.txt';

    $chatterbot->command_interface;

    $string = preprocess($string);

    $string = postprocess($string);

     if ($self->_testquit($user_input) ) { ... }

     $self->_debug_memory()

    $reply = $chatterbot->transform( $string, $use_memory );

        $mybot->memory_on(0);

    $self->parse_script_data;
    $self->parse_script_data( $script_file );

Format of the script file

Each line in the script file can specify a key, a decomposition rule, or a reassembly rule.

  key: remember 5
    decomp: * i remember *
      reasmb: Do you often think of (2) ?
      reasmb: Does thinking of (2) bring anything else to mind ?
    decomp: * do you remember *
      reasmb: Did you think I would forget (2) ?
      reasmb: What about (2) ?
      reasmb: goto what
  pre: equivalent alike
  synon: belief feel think believe wish

The number after the key specifies the rank. If a user's input contains the keyword, then the transform() function will try to match one of the decomposition rules for that keyword. If one matches, then it will select one of the reassembly rules at random. The number (2) here means "use whatever set of words matched the second asterisk in the decomposition rule."

If you specify a list of synonyms for a word, the you should use a "@" when you use that word in a decomposition rule:

  decomp: * i @belief i *
    reasmb: Do you really think so ?
    reasmb: But you are not sure you (3).

Otherwise, the script will never check to see if there are any synonyms for that keyword.

Reassembly rules should be marked with reasm_for_memory rather than reasmb when it is appropriate for use when a user's comment has been extracted from memory.

  key: my 2
    decomp: * my *
      reasm_for_memory: Let's discuss further why your (2).
      reasm_for_memory: Earlier you said your (2).
      reasm_for_memory: But your (2).
      reasm_for_memory: Does that have anything to do with the fact that your (2) ?

How the script file is parsed

Next, it uses the string $entrytype to determine what sort of stuff to expect in the $entry variable, if anything, and parses it accordingly. In some cases, there is no second level of key-value pair, so the function does not even bother to isolate or create $key and $value.

$key is always a single word. $value can be null, or one single word, or a string composed of several words, or an array of words.

Based on all these entries and keys and values, the function creates two giant hashes: %decomplist, which holds the decomposition rules for each keyword, and %reasmblist, which holds the reassembly phrases for each decomposition rule. It also creates %keyranks, which holds the ranks for each key.

Six other arrays are created: "%reasm_for_memory, %pre, %post, %synon, @initial," and @final.

COPYRIGHT AND LICENSE

This is free software; you can redistribute it and/or modify it under the same terms as the Perl 5 programming language system itself.

AUTHOR

Implements the classic Eliza algorithm by Prof. Joseph Weizenbaum. Script format devised by Charles Hayden.