view release on metacpan or  search on metacpan

lib/AI/ExpertSystem/Simple.pm  view on Meta::CPAN

package AI::ExpertSystem::Simple;

use strict;
use warnings;

use XML::Twig;

use AI::ExpertSystem::Simple::Rule;
use AI::ExpertSystem::Simple::Knowledge;
use AI::ExpertSystem::Simple::Goal;

our $VERSION = '1.2';

sub new {
	my ($class) = @_;

	die "Simple->new() takes no arguments" if scalar(@_) != 1;

	my $self = {};

	$self->{_rules} = ();
	$self->{_knowledge} = ();
	$self->{_goal} = undef;
	$self->{_filename} = undef;

	$self->{_ask_about} = undef;
	$self->{_told_about} = undef;

	$self->{_log} = ();

	$self->{_number_of_rules} = 0;
	$self->{_number_of_attributes} = 0;
	$self->{_number_of_questions} = 0;

	return bless $self, $class;
}

sub reset {
	my ($self) = @_;

	die "Simple->reset() takes no arguments" if scalar(@_) != 1;

	foreach my $name (keys %{$self->{_rules}}) {
		$self->{_rules}->{$name}->reset();
	}

	foreach my $name (keys %{$self->{_knowledge}}) {
		$self->{_knowledge}->{$name}->reset();
	}

	$self->{_ask_about} = undef;
	$self->{_told_about} = undef;
	$self->{_log} = ();
}

sub load {
	my ($self, $filename) = @_;

	die "Simple->load() takes 1 argument" if scalar(@_) != 2;
	die "Simple->load() argument 1 (FILENAME) is undefined" if !defined($filename);

	if(-f $filename and -r $filename) {
		my $twig = XML::Twig->new(
			twig_handlers => { goal => sub { $self->_goal(@_) },
					   rule => sub { $self->_rule(@_) },
					   question => sub { $self->_question(@_) } }
		);

		$twig->safe_parsefile($filename);

		die "Simple->load() XML parse failed: $@" if $@;

		$self->{_filename} = $filename;

		$self->_add_to_log( "Read in $filename" );
		$self->_add_to_log( "There are " . $self->{_number_of_rules} . " rules" );
		$self->_add_to_log( "There are " . $self->{_number_of_attributes} . " attributes" );
		$self->_add_to_log( "There are " . $self->{_number_of_questions} . " questions" );
		$self->_add_to_log( "The goal attibutes is " . $self->{_goal}->name() );
		return 1;
	} else {
		die "Simple->load() unable to use file";
	}
}

sub _goal {
	my ($self, $t, $node) = @_;

	my $attribute = undef;
	my $text = undef;

	my $x = ($node->children('attribute'))[0];
	$attribute = $x->text();

	$x = ($node->children('text'))[0];
	$text = $x->text();

	$self->{_goal} = AI::ExpertSystem::Simple::Goal->new($attribute, $text);

	eval { $t->purge(); }
}

sub _rule {
	my ($self, $t, $node) = @_;

	my $name = undef;

	my $x = ($node->children('name'))[0];
	$name = $x->text();

	if(!defined($self->{_rules}->{$name})) {
		$self->{_rules}->{$name} = AI::ExpertSystem::Simple::Rule->new($name);
		$self->{_number_of_rules}++;
	}

	foreach $x ($node->get_xpath('//condition')) {
		my $attribute = undef;
		my $value = undef;

		my $y = ($x->children('attribute'))[0];
		$attribute = $y->text();

		$y = ($x->children('value'))[0];
		$value = $y->text();

		$self->{_rules}->{$name}->add_condition($attribute, $value);

		if(!defined($self->{_knowledge}->{$attribute})) {
			$self->{_number_of_attributes}++;
			$self->{_knowledge}->{$attribute} = AI::ExpertSystem::Simple::Knowledge->new($attribute);
		}
	}

	foreach $x ($node->get_xpath('//action')) {
		my $attribute = undef;
		my $value = undef;

		my $y = ($x->children('attribute'))[0];
		$attribute = $y->text();

		$y = ($x->children('value'))[0];
		$value = $y->text();

		$self->{_rules}->{$name}->add_action($attribute, $value);

		if(!defined($self->{_knowledge}->{$attribute})) {
			$self->{_number_of_attributes}++;
			$self->{_knowledge}->{$attribute} = AI::ExpertSystem::Simple::Knowledge->new($attribute);
		}
	}

	eval { $t->purge(); }
}

sub _question {
	my ($self, $t, $node) = @_;

	my $attribute = undef;
	my $text = undef;
	my @responses = ();

	$self->{_number_of_questions}++;

	my $x = ($node->children('attribute'))[0];
	$attribute = $x->text();

	$x = ($node->children('text'))[0];
	$text = $x->text();

	foreach $x ($node->children('response')) {
		push(@responses, $x->text());
	}

	if(!defined($self->{_knowledge}->{$attribute})) {
		$self->{_number_of_attributes}++;
		$self->{_knowledge}->{$attribute} = AI::ExpertSystem::Simple::Knowledge->new($attribute);
	}
	$self->{_knowledge}->{$attribute}->set_question($text, @responses);

	eval { $t->purge(); }
}

sub process {
	my ($self) = @_;

	die "Simple->process() takes no arguments" if scalar(@_) != 1;

	my $n = $self->{_goal}->name();

	if($self->{_knowledge}->{$n}->is_value_set()) {
		return 'finished';
	}

	if($self->{_ask_about}) {
		my %answers = ();

		$answers{$self->{_ask_about}}->{value} = $self->{_told_about};
		$answers{$self->{_ask_about}}->{setter} = '';

		$self->{_ask_about} = undef;
		$self->{_told_about} = undef;

		while(%answers) {
			my %old_answers = %answers;
			%answers = ();

			foreach my $answer (keys(%old_answers)) {
				my $n = $answer;
				my $v = $old_answers{$answer}->{value};
				my $s = $old_answers{$answer}->{setter};

				$self->_add_to_log( "Setting '$n' to '$v'" );

				$self->{_knowledge}->{$n}->set_value($v,$s);

				foreach my $key (keys(%{$self->{_rules}})) {
					if($self->{_rules}->{$key}->state() eq 'active') {
						my $state = $self->{_rules}->{$key}->given($n, $v);
						if($state eq 'completed') {
							$self->_add_to_log( "Rule '$key' has completed" );
							my %y = $self->{_rules}->{$key}->actions();
							foreach my $k (keys(%y)) {
								$self->_add_to_log( "Rule '$key' is setting '$k' to '$y{$k}'" );
								$answers{$k}->{value} = $y{$k};
								$answers{$k}->{setter} = $key;
							}
						} elsif($state eq 'invalid') {
							$self->_add_to_log( "Rule '$key' is now inactive" );
						}
					}
				}
			}
		}

		return 'continue';
	} else {
		my %scoreboard = ();

		foreach my $rule (keys(%{$self->{_rules}})) {
			if($self->{_rules}->{$rule}->state() eq 'active') {
				my @listofquestions = $self->{_rules}->{$rule}->unresolved();
				my $ok = 1;
				my @questionstoask = ();
				foreach my $name (@listofquestions) {
					if($self->{_knowledge}->{$name}->has_question()) {
						push(@questionstoask, $name);
					} else {
						$ok = 0;
					}
				}

				if($ok == 1) {
					foreach my $name (@questionstoask) {
						$scoreboard{$name}++;
					}
				}
			}
		}

		my $max_value = 0;

		foreach my $name (keys(%scoreboard)) {
			if($scoreboard{$name} > $max_value) {
				$max_value = $scoreboard{$name};
				$self->{_ask_about} = $name;
			}
		}

		return $self->{_ask_about} ? 'question' : 'failed';
	}
}

sub get_question {
	my ($self) = @_;

	die "Simple->get_question() takes no arguments" if scalar(@_) != 1;

	return $self->{_knowledge}->{$self->{_ask_about}}->get_question();
}

sub answer {
	my ($self, $value) = @_;

	die "Simple->answer() takes 1 argument" if scalar(@_) != 2;
	die "Simple->answer() argument 1 (VALUE) is undefined" if ! defined($value);

	$self->{_told_about} = $value;
}

sub get_answer {
	my ($self) = @_;

	die "Simple->get_answer() takes no arguments" if scalar(@_) != 1;

	my $n = $self->{_goal}->name();

	return $self->{_goal}->answer($self->{_knowledge}->{$n}->get_value());
}

sub log {
	my ($self) = @_;

	die "Simple->log() takes no arguments" if scalar(@_) != 1;

	my @return = ();
	@return = @{$self->{_log}} if defined @{$self->{_log}};

	$self->{_log} = ();

	return @return;
}

sub _add_to_log {
	my ($self, $message) = @_;

	push( @{$self->{_log}}, $message );
}

sub explain {
	my ($self) = @_;

	die "Simple->explain() takes no arguments" if scalar(@_) != 1;

	my $name  = $self->{_goal}->name();
	my $rule  = $self->{_knowledge}->{$name}->get_setter();
	my $value = $self->{_knowledge}->{$name}->get_value();

	my $x = "The goal '$name' was set to '$value' by " . ($rule ? "rule '$rule'" : 'asking a question' );
	$self->_add_to_log( $x );

	my @processed_rules;
	push( @processed_rules, $rule ) if $rule;

	$self->_explain_this( $rule, '', @processed_rules );
}

sub _explain_this {
	my ($self, $rule, $depth, @processed_rules) = @_;

	$self->_add_to_log( "${depth}Explaining rule '$rule'" );

	my %dont_do_these = map{ $_ => 1 } @processed_rules;

	my @check_these_rules = ();

	my %conditions = $self->{_rules}->{$rule}->conditions();
	foreach my $name (sort keys %conditions) {
		my $value = $conditions{$name};
		my $setter = $self->{_knowledge}->{$name}->get_setter();

		my $x = "$depth Condition '$name' was set to '$value' by " . ($setter ? "rule '$setter'" : 'asking a question' );
		$self->_add_to_log( $x );

		if($setter) {
			unless($dont_do_these{$setter}) {
				$dont_do_these{$setter} = 1;
				push( @check_these_rules, $setter );
			}
		}
	}

	my %actions = $self->{_rules}->{$rule}->actions();
	foreach my $name (sort keys %actions) {
		my $value = $actions{$name};

		my $x = "$depth Action set '$name' to '$value'";
		$self->_add_to_log( $x );
	}

	@processed_rules = keys %dont_do_these;

	foreach my $x ( @check_these_rules ) {
		push( @processed_rules, $self->_explain_this( $x, "$depth ", keys %dont_do_these ) );
	}

	return @processed_rules;
}

1;

=head1 NAME

AI::ExpertSystem::Simple - A simple expert system shell

=head1 VERSION

This document refers to verion 1.2 of AI::ExpertSystem::Simple, released June 10, 2003

=head1 SYNOPSIS

This class implements a simple expert system shell that reads the rules from an XML 
knowledge base and questions the user as it attempts to arrive at a conclusion.

=head1 DESCRIPTION

=head2 Overview

This class is where all the work is being done and the other three classes are only 
there for support. At present there is little you can do with it other than run it. Future 
version will make subclassing of this class feasable and features like logging will be introduced.

To see how to use this class there is a simple shell in the bin directory which allows you 
to consult the example knowledge bases and more extensive documemtation in the docs directory.

There is a Ruby version that reads the same XML knowledge bases, if you are interested.

=head2 Constructors and initialisation

=over 4

=item new( )

The constructor takes no arguments and just initialises a few basic variables.

=back

=head2 Public methods

=over 4

=item reset( )

Resets the system back to its initial state so that a new consoltation can be run

=item load( FILENAME )

This method takes the FILENAME of an XML knowledgebase and attempts to parse it to set up the data structures 
required for a consoltation.

=item process( )

Once the knowledgebase is loaded the consultation is run by repeatedly calling this method.

It returns four results:

=over 4