package MyClass;

use strict;
use warnings;

use DBI;
use base qw(Class::DBI::Pg);

{
   __PACKAGE__->connection("dbi:Pg:dbname=mydb", 'some-user', 'some-password', 
                                               { RaiseError => 1, AutoCommit => 1 });
 }
########################################################
package MyClass::Event;

use base qw/MyClass/;

_PACKAGE__->set_up_table('event');
__PACKAGE__->has_a(signature => 'MyClass::Signature');


########################################################
package MyClass::Signature;

use base qw/MyClass/;

_PACKAGE__->set_up_table('signature');
__PACKAGE__->has_many(events => 'MyClass::Event' => signature);

# ....