#===================================
sub inherited_permission {
#===================================
    my $self = shift;
    unless (defined $self->{_inh}) {
        my $object = $self->object;
        my $object_parent_id = $object->parent_id;
        my @object_groups = $object->groups;
        my $own_object_id = $object->id;
        my @object_ids = (
            $own_object_id,
            @object_groups,
            $object_parent_id
        );

        my $subject = $self->subject;
        my $subject_parent_id = $subject->parent_id;
        my @subject_groups = $subject->groups;
        
        my $own_subject_id = $subject->id;
        my @subject_ids = (
            $own_subject_id,
            @subject_groups,
            $subject_parent_id
        );

        my $inherited_permission = $self->permission;
        foreach my $object_id (@object_ids) {
            foreach my $subject_id (@subject_ids) {
                next if !($subject_id && $object_id)
                        || ($subject_id == $own_subject_id 
                            && $object_id == $own_object_id);
                            
                my $permission = $self->new({
                    object   => $self->base_class->new($object_id),
                    subject  => $self->base_class->new($subject_id)
                });
                $inherited_permission|=$permission->inherited_permission;
            }
        }
        $self->{_inh} = $inherited_permission & $self->mask;
        my @saved = delete @{$self}{'_subject','_object'};
        $self->save_to_cache;
        @{$self}{'_subject','_object'}= @saved;
    }
    return $self->{_inh};
}