sub get_list {
    my ($class, %args) = @_;
    my ($id_name,$table) = @args{qw(_id _table)};
    my $sql = "SELECT $id_name FROM $table";

    # the database object is deliberately unavailable to the
    # programmers
    my @objects;
    my $ids = $DBO->_arrayref( $sql );
    foreach my $id ( @$ids ) {
        push @objects => $class->new(%args,open_id => $id);
    }
    return \@objects;
}