belkajm sent me a great bit of code to handle the unification problem in AI::Perlog, of which you can download the latest copy at this link. Unfortunately, belkajm didn't make his post a root node, which I think it should have been because it was a very well-explained solution to the problem. Go vote for it :)

To show how interesting this is (to me, at least), consider the problem listed in Who's a thief?. The code I have below solves the listed problem. You can compare this to code in AI in Perl - proof of concept. That code is much clumsier, less scalable, and not as easy to modify.

Also, I want to take a closer look at the code that arhuman put together in AI::Perlog(2) unification proposition and an explanatory follow-up. It has some interesting features that I hadn't considered, but also haven't had the time to delve into. All in all, I have to say "thanks" to both arhuman and belkajm for their help and am looking forward to seeing more.

Enjoy!

#!/usr/bin/perl -w
use strict;
use AI::Perlog;

my $pg = AI::Perlog->new;
load_data();

my $acts_of_horror = who_steals_from_whom();

unless ( @$acts_of_horror ) {
    print "Looks like everybody's safe\n";
}
else {
    foreach my $crime ( @$acts_of_horror ) {
        my ( $thief, $victim ) = @$crime;
        print "$thief will steal from $victim.\n";
    }
}

exit;

sub who_steals_from_whom {
    my $thieves = $pg->thief( '$person' );
    my $victims = $pg->owns( qw/ $person _ / );

    my @crimes;
    foreach my $victim ( @$victims ) {
        my $curr_victim = $victim->{person};
        foreach my $thief ( @$thieves ) {
            my $curr_thief = $thief->{person};
            if (rich($curr_victim) and ! $pg->knows($curr_thief,$curr_
+victim)){
                push @crimes =>  [$curr_thief, $curr_victim];
            }
        }
    }
    return \@crimes;
}

sub rich {
    my $person = shift;
    my $items = $pg->owns( $person, '$item' );
    local $_;
    foreach ( @$items ) {
        return 1 if $pg->valuable( $_->{ item } );
    }
    return;
}

sub load_data {
    while ( <DATA> ) {
        chomp;
        next if ( ! $_ or substr( $_, 0, 1 ) eq '#' );
        my @fact = split /\t/;
        $pg->add_fact( @fact );
    }
}

__DATA__
owns    merlyn    gold
owns    Ovid    pocket lint
owns    Ovid    cheap whiskey
owns    kudra    domination fund

valuable    gold
valuable    domination fund

thief    badguy
thief    badgirl

# :)
knows    badgirl    merlyn

[download]

Cheers,
Ovid

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In reply to AI::Perlog - more thieves by Ovid

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