private void WriteSimpleType (DataColumn col)
{
w.WriteStartElement ("xs", "simpleType", xmlnsxs);
w.WriteStartElement ("xs", "restriction", xmlnsxs);
w.WriteStartAttribute ("base", String.Empty);
WriteQName (MapType (col.DataType));
w.WriteEndAttribute ();
w.WriteStartElement ("xs", "maxLength", xmlnsxs);
w.WriteAttributeString ("value",
XmlConvert.ToString (col.MaxLength));
w.WriteEndElement (); // maxLength
w.WriteEndElement (); // restriction
w.WriteEndElement (); // simpleType
}