sub location {
    my $self = shift;

    my $expat = $self->{Expat};

    my @properties = ( ColumnNumber => $expat->current_column,
		       LineNumber => $expat->current_line,
		       BytePosition => $expat->current_byte,
		       Base => $expat->base );

    # FIXME these locations change while parsing external entities
    push (@properties, PublicId => $self->{Source}{PublicId})
	if (defined $self->{Source}{PublicId});
    push (@properties, SystemId => $self->{Source}{SystemId})
	if (defined $self->{Source}{SystemId});

    return { @properties };
}