README file for Chatbot::Eliza 1.04
NAME
Chatbot::Eliza - A clone of the classic Eliza program
SYNOPSIS
use Chatbot::Eliza;
$mybot = new Chatbot::Eliza;
$mybot->command_interface;
# see below for details
DESCRIPTION
This module implements the classic Eliza algorithm. The original
Eliza program was written by Joseph Weizenbaum and described in
the Communications of the ACM in 1966. Eliza is a mock Rogerian
psychotherapist. It prompts for user input, and uses a simple
transformation algorithm to change user input into a follow-up
question. The program is designed to give the appearance of
understanding.
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
The current version of Chatbot::Eliza.pm is available on CPAN:
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
This is all you need to do to launch a simple Eliza session:
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
Each Eliza object uses the following data structures to hold the
script data in memory:
%decomplist
*Hash*: the set of keywords; *Values*: strings containing the
decomposition rules.
%reasmblist
*Hash*: a set of values which are each the join of a keyword and
a corresponding decomposition rule; *Values*: the set of
possible reassembly statements for that keyword and
decomposition rule.
%reasmblist_for_memory
This structure is identical to `%reasmblist', except that these
rules are only invoked when a user comment is being retrieved
from memory. These contain comments such as "Earlier you
mentioned that...," which are only appropriate for remembered
comments. Rules in the script must be specially marked in order
to be included in this list rather than `%reasmblist'. The
default script only has a few of these rules.
@memory
A list of user comments which an Eliza instance is remembering
for future use. Eliza does not remember everything, only some
things. In this implementation, Eliza will only remember
comments which match a decomposition rule which actually has
reassembly rules that are marked with the keyword
"reasm_for_memory" rather than the normal "reasmb". The default
script only has a few of these.
%keyranks
*Hash*: the set of keywords; *Values*: the ranks for each
keyword
@quit
"quit" words -- that is, words the user might use to try to exit
the program.
@initial
Possible greetings for the beginning of the program.
@final
Possible farewells for the end of the program.
%pre
*Hash*: words which are replaced before any transformations;
*Values*: the respective replacement words.
%post
*Hash*: words which are replaced after the transformations and
after the reply is constructed; *Values*: the respective
replacement words.
%synon
*Hash*: words which are found in decomposition rules; *Values*:
words which are treated just like their corresponding synonyms
during matching of decomposition rules.
Other data members
There are several other internal data members. Hopefully these
are sufficiently obvious that you can learn about them just by
reading the source code.
METHODS
new()
my $chatterbot = new Chatbot::Eliza;
new() creates a new Eliza object. This method also calls the
internal _initialize() method, which in turn calls the
parse_script_data() method, which initializes the script data.
my $chatterbot = new Chatbot::Eliza 'Ahmad', 'myfile.txt';
The eliza object defaults to the name "Eliza", and it contains
default script data within itself. However, using the syntax
above, you can specify an alternative name and an alternative
script file.
See the method parse_script_data(). for a description of the
format of the script file.
command_interface()
$chatterbot->command_interface;
command_interface() opens an interactive session with the Eliza
object, just like the original Eliza program.
If you want to design your own session format, then you can
write your own while loop and your own functions for prompting
for and reading user input, and use the transform() method to
generate Eliza's responses. (*Note*: you do not need to invoke
preprocess() and postprocess() directly, because these are
invoked from within the transform() method.)
But if you're lazy and you want to skip all that, then just use
command_interface(). It's all done for you.
During an interactive session invoked using command_interface(),
you can enter the word "debug" to toggle debug mode on and off.
You can also enter the keyword "memory" to invoke the
_debug_memory() method and print out the contents of the Eliza
instance's memory.
preprocess()
$string = preprocess($string);
preprocess() applies simple substitution rules to the input
string. Mostly this is to catch varieties in spelling,
misspellings, contractions and the like.
preprocess() is called from within the transform() method. It is
applied to user-input text, BEFORE any processing, and before a
reassebly statement has been selected.
It uses the array `%pre', which is created during the parse of
the script.
postprocess()
$string = postprocess($string);
postprocess() applies simple substitution rules to the
reassembly rule. This is where all the "I"'s and "you"'s are
exchanged. postprocess() is called from within the transform()
function.
It uses the array `%post', created during the parse of the
script.
_testquit()
if ($self->_testquit($user_input) ) { ... }
_testquit() detects words like "bye" and "quit" and returns true
if it finds one of them as the first word in the sentence.
These words are listed in the script, under the keyword "quit".
_debug_memory()
$self->_debug_memory()
_debug_memory() is a special function which returns the contents
of Eliza's memory stack.
transform()
$reply = $chatterbot->transform( $string, $use_memory );
transform() applies transformation rules to the user input
string. It invokes preprocess(), does transformations, then
invokes postprocess(). It returns the tranformed output string,
called `$reasmb'.
The algorithm embedded in the transform() method has three main
parts:
1 Search the input string for a keyword.
2 If we find a keyword, use the list of decomposition rules for
that keyword, and pattern-match the input string against
each rule.
3 If the input string matches any of the decomposition rules, then
randomly select one of the reassembly rules for that
decomposition rule, and use it to construct the reply.
transform() takes two parameters. The first is the string we
want to transform. The second is a flag which indicates where
this sting came from. If the flag is set, then the string has
been pulled from memory, and we should use reassembly rules
appropriate for that. If the flag is not set, then the string is
the most recent user input, and we can use the ordinary
reassembly rules.
The memory flag is only set when the transform() function is
called recursively. The mechanism for setting this parameter is
embedded in the transoform method itself. If the flag is set
inappropriately, it is ignored.
How memory is used
In the script, some reassembly rules are special. They are
marked with the keyword "reasm_for_memory", rather than just
"reasm". Eliza "remembers" any comment when it matches a
docomposition rule for which there are any reassembly rules for
memory. An Eliza object remembers up to `$max_memory_size'
(default: 5) user input strings.
If, during a subsequent run, the transform() method fails to
find any appropriate decomposition rule for a user's comment,
and if there are any comments inside the memory array, then
Eliza may elect to ignore the most recent comment and instead
pull out one of the strings from memory. In this case, the
transform method is called recursively with the memory flag.
Honestly, I am not sure exactly how this memory functionality
was implemented in the original Eliza program. Hopefully this
implementation is not too far from Weizenbaum's.
If you don't want to use the memory functionality at all, then
you can disable it:
$mybot->memory_on(0);
You can also achieve the same effect by making sure that the
script data does not contain any reassembly rules marked with
the keyword "reasm_for_memory". The default script data only has
4 such items.
parse_script_data()
$self->parse_script_data;
$self->parse_script_data( $script_file );
parse_script_data() is invoked from the _initialize() method,
which is called from the new() function. However, you can also
call this method at any time against an already-instantiated
Eliza instance. In that case, the new script data is *added* to
the old script data. The old script data is not deleted.
You can pass a parameter to this function, which is the name of
the script file, and it will read in and parse that file. If you
do not pass any parameter to this method, then it will read the
data embedded at the end of the module as its default script
data.
If you pass the name of a script file to parse_script_data(),
and that file is not available for reading, then the module
dies.
Format of the script file
This module includes a default script file within itself, so it
is not necessary to explicitly specify a script file when
instantiating an Eliza object.
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
Each line in the script file contains an "entrytype" (key,
decomp, synon) and an "entry", separated by a colon. In turn,
each "entry" can itself be composed of a "key" and a "value",
separated by a space. The parse_script_data() function parses
each line out, and splits the "entry" and "entrytype" portion of
each line into two variables, `$entry' and `$entrytype'.
Next, it uses the string `$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'.
CHANGES
* Version 1.02-1.04 - January 2003
Added a Norwegian script, kindly contributed by
Mats Stafseng Einarsen. Thanks Mats!
* Version 1.01 - January 2003
Added an empty DESTORY method, to eliminate
some pesky warning messages. Suggested by
Stas Bekman.
* Version 0.98 - March 2000
Some changes to the documentation.
* Versions 0.96-0.97 - October 1999
One tiny change to the regex which implements
reassemble rules. Thanks to Gidon Wise for
suggesting this improvement.
* Versions 0.94-0.95 - July 1999
Fixed a bug in the way the bot invokes its random function
when it pulls a comment out of memory.
* Version 0.93 - June 1999
Calling programs can now 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.
You can also now use a reference to an anonymous hash
as a parameter to the new() method to define any fields
in that bot instance:
$bot = new Chatbot::Eliza {
name => "Brian",
scriptfile => "myscript.txt",
debug => 1,
};
* Versions 0.91-0.92 - April 1999
Fixed some misspellings.
* Version 0.90 - April 1999
Fixed a bug in the way individual bot objects store
their memory. Thanks to Randal Schwartz and to
Robert Chin for pointing this out.
Fixed a very stupid error in the way the random
function is invoked. Thanks to Antony Quintal
for pointing out the error.
Many corrections and improvements were made
to the German script by Matthias Hellmund.
Thanks, Matthias!
Made a minor syntactical change, at the suggestion
of Roy Stephan.
The memory functionality can now be disabled by setting the
$Chatbot::Eliza::memory_on variable to 0, like so:
$bot->memory_on(0);
Thanks to Robert Chin for suggesting that.
* Version 0.40 - July 1998
Re-implemented the memory functionality.
Cleaned up and expanded the embedded POD documentation.
Added a sample script in German.
Modified the debugging behavior. The transform() method itself
will no longer print any debugging output directly to STDOUT.
Instead, all debugging output is stored in a module variable
called "debug_text". The "debug_text" variable is printed out
by the command_interface() method, if the debug flag is set.
But even if this flag is not set, the variable debug_text
is still available to any calling program.
Added a few more example scripts which use the module.
simple - simple script using Eliza.pm
simple.cgi - simple CGI script using Eliza.pm
debug.cgi - CGI script which displays debugging output
deutsch - script using the German script
deutsch.cgi - CGI script using the German script
twobots - script which creates two distinct bots
* Version 0.32 - December 1997
Fixed a bug in the way Eliza loads its default internal script data.
(Thanks to Randal Schwartz for pointing this out.)
Removed the "memory" functions internal to Eliza.
When I get them working properly I will add them back in.
Added one more example program.
Fixed some minor errors in the embedded POD documentation.
* Version 0.31
The module is now installable, just like any other self-respecting
CPAN module.
* Version 0.30
First release.
AUTHOR
John Nolan
[email protected] January 2003.
Implements the classic Eliza algorithm by Prof. Joseph
Weizenbaum. Script format devised by Charles Hayden.
